Photography glossary

From the camera obscura and early photographic plates to roll film, autofocus SLRs and digital reflex cameras: 636 terms for reading old manuals, understanding equipment and making photographs.

This glossary covers photographic processes, camera designs, lenses, exposure, lighting, darkroom work and DSLR-era digital imaging. Film rangefinders and view cameras belong here too. The boundary is technological rather than a cut-off year: DSLRs and digital mirrorless cameras overlapped.

Choose a letter, search the glossary, or follow a linked term. Dimensions labelled as format names are often nominal; compatibility and processing instructions should always be checked against the exact equipment or material.

0-9

4 × 5 #

A large-format sheet-film size measured in inches, also written 5 × 4. It describes the sheet, rather than the exact exposed image area.

6 × 6 #

A nominal medium-format frame size, usually around 56 × 56 mm on 120 or 220 film. Other nominal sizes include 6 × 4.5, 6 × 7, 6 × 8 and 6 × 9.

8 × 10 #

A large-format sheet-film size in inches, also written 10 × 8. It permits a sizeable contact print without enlargement.

16 mm subminiature #

Still photography using film 16 mm wide, supplied in various proprietary cassettes or loaded from bulk stock. Image dimensions and perforation requirements depend on the camera.

35 mm film #

Perforated film 35 mm wide, most commonly used for 24 × 36 mm still photographs. The film width and the picture dimensions are different measurements. See 135 film and Half-frame.

110 film #

Cartridge film producing a nominal 13 × 17 mm image, used in pocket cameras. Its small negative needs substantial enlargement for a conventional print.

120 film #

Paper-backed roll film used by many medium-format cameras. The camera determines the frame size, such as 6 × 4.5, 6 × 6 or 6 × 9 cm; these are nominal format names.

126 film #

Cartridge film associated with Instamatic cameras, usually making square images approximately 28 × 28 mm. It is unrelated to 120 roll film.

127 film #

Roll film narrower than 120, used by cameras including the original Vest Pocket Kodak and some small twin-lens reflex cameras. Frame dimensions depend on the camera.

135 film #

The standard daylight-loading cassette designation for 35 mm still-camera film. Most full-frame cameras make 24 × 36 mm exposures on it.

220 film #

Medium-format roll film with paper leader and trailer but no continuous backing paper behind the image area. It gives roughly twice the exposures of 120 and requires compatible film transport and pressure-plate arrangements.

620 film #

Film with the same width as 120 but wound on a different spool with smaller end flanges and core. A camera accepting 620 does not necessarily accept a 120 spool.

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A

Aberration #

An optical imperfection that prevents a lens from reproducing an ideal image. Examples include spherical aberration, coma, astigmatism, field curvature and chromatic aberration.

Achromat #

A lens arrangement that brings two selected wavelengths towards a common focus, reducing chromatic aberration. An achromatic doublet commonly combines two different optical glasses.

Actinic #

Capable of producing a photochemical effect. Actinic light is defined by its effect on a particular material, not merely by how bright it looks to the eye.

Active autofocus #

Automatic focusing that sends out a signal, such as infrared light or ultrasound, to estimate subject distance. Glass, dark surfaces and distant subjects can cause difficulties, depending on the system.

Acutance #

The apparent crispness of boundaries between light and dark areas. High acutance can make an image look sharp even when its ability to resolve very fine detail is modest.

Adapter #

A fitting used to join equipment with different interfaces, usually a lens and camera. Physical attachment does not guarantee infinity focus, aperture control, metering or autofocus.

Additive colour #

Colour formation by combining light, usually red, green and blue. Early screen-plate processes and electronic displays use additive principles; colour dyes in most prints work subtractively.

AE #

Automatic exposure: the camera selects one or more exposure settings from its meter reading. The photographer still needs to choose how the subject should be rendered and check operating limits.

AE lock #

Autoexposure lock: holds a metered exposure while the photographer recomposes or waits. Whether it also locks flash exposure or focus depends on the camera.

Aerial image #

An optical image formed in space without a focusing screen at that position. Some specialised finder and focusing systems use it for inspection.

AF #

Autofocus: automatic adjustment of lens focus. AF mode, point selection and subject tracking are separate controls on many cameras.

AF assist #

Light or a projected pattern used to help autofocus in poor conditions. It is separate from the flash that illuminates the recorded exposure.

AF lock #

Autofocus lock: holds a focus distance rather than allowing the camera to refocus. It is useful for recomposing but can introduce focus errors at close distances and wide apertures.

AF microadjustment #

A DSLR setting that offsets the camera’s separate phase-detection autofocus calibration for a lens. It does not repair optical faults or guarantee accuracy at every focal length and distance.

AF-D #

A Nikon designation indicating that a lens supplies focus-distance information for compatible metering and flash systems. D does not by itself specify an in-lens autofocus motor.

AF-S #

In Nikon lens names, identifies an in-lens Silent Wave Motor focusing design. In camera focus-mode menus, AF-S commonly means single-servo autofocus; the two uses should not be confused.

Agitation #

Movement of film, paper or chemistry during processing to renew solution at the emulsion surface. The pattern and frequency affect development evenness and contrast.

AI coupling #

Nikon’s Automatic Indexing aperture-coupling arrangement for compatible F-mount lenses and cameras. Earlier non-AI lenses can damage some bodies if fitted without the required modification or allowance.

AI-S #

A development of Nikon’s AI lens specification with aperture-control characteristics used by certain bodies. It does not mean the lens has autofocus.

Air release #

A pneumatic shutter release using a bulb and flexible tube. Air pressure operates a small piston at the camera, allowing release without touching the body.

Air-spaced #

Describes lens elements separated by an air gap rather than cemented together. The gap is part of the optical design and should not be altered casually.

Albumen print #

A photographic paper print with an egg-white binder carrying the image-forming silver. Its smooth surface helped make finely detailed nineteenth-century prints from glass negatives.

Aliasing #

False patterns or jagged boundaries caused when image detail exceeds the sampling ability of a digital sensor. Moiré is one visible form.

Ambient light #

Light already present in the scene, whether daylight or artificial illumination. Flash can supplement it, overpower it or be balanced with it.

Ambrotype #

A collodion image on glass that looks positive against a dark backing. The image itself is a thin negative, and the usual result is a unique object.

Anastigmat #

A lens corrected to reduce astigmatism and associated off-axis image problems. The marking describes a design goal, not a guarantee of perfect performance.

Angle of view #

The angular extent of the scene recorded by a particular lens and image format. The same focal length covers a narrower angle on a smaller format.

Anti-aliasing filter #

An optical low-pass filter ahead of a sensor that slightly spreads fine detail to reduce moiré and false colour. Some DSLRs omit or cancel its blurring effect.

Anti-curl layer #

A coating intended to balance stresses in photographic film and reduce curling. It is one of several layers that may be present beyond the light-sensitive emulsion.

Anti-halation layer #

A film layer or backing that absorbs stray light after it passes through the emulsion, reducing halos caused by reflections from the film base or camera interior.

Anti-reflection coating #

A thin optical coating that reduces reflections at glass surfaces, improving light transmission and limiting flare. Single coatings and multicoatings differ in construction and effectiveness.

Aperture #

The opening that admits light through a lens. Its diameter affects image brightness, depth of field and diffraction; the f-number relates that diameter to focal length.

Aperture priority #

An automatic exposure mode in which the photographer selects the aperture and the camera chooses shutter speed. Common dial markings are A and Av.

Aperture ring #

A lens ring used to select the diaphragm setting. On some electronic cameras it is replaced by a body control; an A position may hand control to the camera.

APEX #

Additive System of Photographic Exposure: a logarithmic system for expressing exposure quantities. Av and Tv survive as labels for aperture and shutter-speed values and exposure modes.

Apochromat #

A lens with more extensive colour correction than a basic achromat. APO is a common marking, but manufacturers’ design criteria and marketing usage vary.

APS film #

Advanced Photo System: a cartridge-based film system using 24 mm-wide film. Its H, C and P print choices generally specify different crops of the recorded frame.

APS-C #

A digital sensor format smaller than 24 × 36 mm, widely used in DSLRs. Dimensions vary by maker; common crop factors are approximately 1.5× and 1.6×.

APS-H #

A designation used for some digital sensors between APS-C and 24 × 36 mm in size. Canon’s DSLR implementation is about a 1.3× crop; the name does not specify one universal dimension.

Archival #

Intended for long-term preservation. No material lasts indefinitely: processing, enclosure, temperature, humidity, light exposure and digital migration all affect survival.

ASA #

An older arithmetic film-speed scale associated with the American Standards Association. Its familiar numbers, such as 100 and 400, continue in the arithmetic part of ISO film ratings.

Aspect ratio #

The relationship between image width and height, such as 3:2, 4:3 or 1:1. It is independent of the size at which the image is displayed.

Aspherical element #

A lens element with at least one surface that is not part of a sphere. It can help correct aberrations or reduce the number of elements required.

Astigmatism #

An aberration in which differently oriented detail away from the optical axis focuses at different positions. An off-centre point may appear stretched rather than sharply rendered.

Autochrome #

An early commercial colour transparency process using a screen of dyed starch grains on a glass plate. It records colour through an additive screen rather than modern colour-film dye layers.

Autofocus #

A system that adjusts focus automatically. Film and DSLR cameras use several methods, including active ranging, dedicated phase detection and image-sensor contrast detection.

Autographic film #

A historical roll-film arrangement allowing notes to be written through an opening in a compatible camera back and photographically recorded on the film margin.

Automatic diaphragm #

A mechanism that holds the lens open for viewing and stops it down to the selected aperture for exposure. Older preset and manual diaphragms require different handling.

Available light #

Existing illumination used to make a photograph without adding a separate light source. Often used for low-light work, although the term also includes bright daylight.

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B

Back #

A camera’s rear assembly, which may carry film, a ground glass, a digital sensor or processing mechanisms for instant material. Interchangeable backs are common in some medium- and large-format systems.

Back focus #

Can mean the distance behind a lens to its image plane, or an autofocus fault where sharp focus falls behind the intended subject. Establish the context before interpreting a specification.

Back-button focus #

Assigning autofocus activation to a rear camera button, separate from the shutter release. The arrangement can help control when continuous autofocus starts and stops.

Backing paper #

Opaque paper protecting roll film from light and carrying frame numbers for some cameras. It does not make exposed film safe to handle in daylight once separated from the film.

Backlight #

Illumination from behind the subject towards the camera. It can produce silhouettes, glowing edges and flare, and may mislead a reflective exposure meter.

Bag bellows #

A flexible, bag-shaped bellows used on view cameras, especially with wide-angle lenses. It allows movements at short lens-to-film distances where pleated bellows can become restrictive.

Ball head #

A tripod head with a ball-and-socket joint that allows movement in several directions. Locking strength and resistance to creeping matter with heavy equipment.

Banding #

Unwanted stripes in an image, caused by effects such as electronic readout noise, uneven lighting or flickering lamps. Tonal banding can also describe visible steps in a smooth gradient.

Barn doors #

Adjustable flaps on a lighting fixture that control spill. They shape where light goes but do not necessarily create a sharply focused edge.

Barnack camera #

A name commonly used for early Leica screw-mount cameras and related designs associated with Oskar Barnack. It is a historical family description, not a lens-mount specification.

Barrel distortion #

Geometric distortion that bows straight lines outwards near the frame edges. It differs from converging verticals caused by camera position.

Barrel lens #

A lens supplied without an integral shutter, historically used with a separate shutter, lens cap or timed exposure. A lens barrel can also simply mean a lens’s mechanical housing.

Baryta #

A barium sulphate coating beneath the emulsion of many fibre-based photographic papers. It helps provide a smooth, bright support for the image.

Base plus fog #

The minimum density contributed by the film support and unwanted background density after processing. It is a reference point when assessing a negative‘s useful image densities.

Baseboard #

The platform supporting an enlarger or, in some cameras, the folding bed. Context determines which part is meant.

Battery check #

A camera or meter function indicating whether the power supply meets a specified condition. Passing it does not prove shutter, meter or autofocus accuracy.

Bayer array #

A common sensor colour-filter arrangement repeating red, green and blue filters, usually with twice as many green sites as red or blue. Full-colour output requires demosaicing.

Bayonet mount #

A fitting that locks by inserting and turning mating lugs. Different bayonet systems are generally incompatible even when their diameters look similar.

Beam splitter #

An optical component dividing light into two paths. Cameras use beam splitters for some viewing, focusing, metering and specialised colour-recording arrangements.

Bellows #

A light-tight flexible connection between camera sections, or an extension accessory for close-up photography. Extra extension increases magnification and can require additional exposure.

Bellows factor #

Exposure compensation for increased lens extension. For a simple approximately symmetrical lens, the exposure multiplier is roughly (extension / focal length) squared. At twice the focal length, the multiplier is four, or two stops. More complex lenses may need a pupil-magnification correction.

Between-lens shutter #

A shutter located within a lens assembly, usually a leaf shutter. It commonly permits flash synchronisation over a wider range of speeds than a focal-plane shutter.

Bit depth #

The number of bits used to encode a value. A 14-bit raw channel can represent more numerical levels than an 8-bit channel, but bit depth alone does not determine usable dynamic range.

Black and white #

Photography rendered without the original scene’s full colour information, usually as tones of grey. The image may contain silver, dyes, pigments or digital values.

Black point #

The tonal value mapped to output black during printing or editing. Moving it can strengthen contrast while discarding shadow detail.

Bleach #

A processing chemical that alters or removes an image substance. Colour processing commonly converts developed silver so that it can be removed, leaving a dye image.

Blix #

A combined bleach-fix bath used in some colour processes. It is not interchangeable with a separate bleach or fixer without a process designed for it.

Blooming #

In digital imaging, charge overflow from a saturated photosite into neighbouring areas, particularly associated with some CCDs. In older lens descriptions, blooming can mean an anti-reflection coating.

Blown highlights #

Bright image areas recorded or rendered without recoverable tonal detail. A clipped JPEG preview does not always prove that every raw colour channel is clipped.

Bokeh #

The character of out-of-focus rendering, including blur boundaries, highlights and background texture. It describes blur quality rather than simply how much blur is present.

Box camera #

A simple camera built around a rigid box, usually with limited focusing and exposure controls. Many made roll-film photography accessible to beginners.

Bracketing #

Making a series with deliberately varied settings, commonly exposure. It can provide alternatives or source images for techniques such as HDR and focus stacking.

Breech-lock mount #

A lens mounting arrangement secured by a rotating collar or locking ring. The lens itself need not rotate against the body’s mating surface during attachment.

Bridge camera #

A fixed-lens camera offering more extensive controls or a larger zoom range than a simple compact. It may resemble an SLR externally without having a reflex mirror.

Bright-line finder #

A viewfinder showing illuminated or bright framing outlines. The outlines indicate approximate picture coverage and may shift to compensate for parallax.

Brilliant finder #

A small reflex finder with a lens that presents a bright miniature viewing image. Common on older box and folding cameras, it is mainly a framing aid rather than a precise focusing screen.

Broad lighting #

Portrait lighting in which the side of the face turned towards the camera receives the main illumination. Its effect depends on head angle and the position of the light.

Bromide paper #

Black-and-white photographic paper using an emulsion containing silver bromide. The term is closely associated with developing-out papers suitable for enlargement.

Bromoil #

A printing process in which a silver print is bleached and its gelatin prepared to accept oily ink selectively. The final appearance is shaped by hand inking.

Bronzing #

A metallic-looking surface effect in some prints, visible at particular angles. The cause depends on the image material and process, so the word alone is not a diagnosis.

Bubble level #

A spirit level used to align a camera or support. Keeping the camera level can help with architectural framing and stitched panoramas.

Buffer #

Temporary memory holding image data while the camera processes and writes files. A full buffer can reduce continuous shooting speed even with space left on the card.

Bulb #

A shutter setting, usually B, that holds the shutter open while the release remains engaged. Some electronic cameras offer a press-to-start, press-to-stop variant.

Bulk loading #

Loading lengths of film from a larger roll into reusable cassettes. The emulsion must remain protected from light throughout the appropriate loading stages.

Burning-in #

Giving a selected part of a print extra exposure under an enlarger, usually to darken it. Digital burning tools apply a related local tonal adjustment.

Burst mode #

Continuous shooting while the shutter release is held or otherwise activated. The sustained rate depends on settings, autofocus, shutter speed, buffer and storage performance.

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C

C-41 #

A standard chromogenic colour-negative processing sequence. Some black-and-white films also use C-41 and form dye images rather than conventional silver-only images.

C-type print #

A chromogenic colour print, usually made on colour photographic paper from a negative or digital exposure. It is a chemical photographic print, not a general term for every colour print.

Cabinet card #

A mounted photographic portrait format larger than a carte de visite. The term describes the presentation format, not a unique photographic chemistry.

Cabinet portrait #

A portrait presented as a cabinet card. It identifies a historical mount format rather than a specific lens or camera type.

Cable release #

A flexible mechanical cable whose inner plunger operates a threaded shutter-release socket. Electronic remote releases perform a similar job but use a different interface.

Callier effect #

A difference in the apparent printing density of a scattering photographic image under different illumination geometries. It helps explain why condenser and diffusion enlargers can print the same negative differently.

Calotype #

An early developed paper-negative process associated with William Henry Fox Talbot. A negative could make several positive prints, unlike the usual unique daguerreotype.

Camera lucida #

An optical drawing aid that lets an artist see the subject and drawing surface together. It does not project an image onto sensitised material in the way a camera obscura does.

Camera movements #

See Movements: adjustments of lens and image standards used to control framing and the orientation of sharp focus.

Camera obscura #

A darkened chamber or box in which an opening or lens forms an inverted image of an outside scene. The optical principle predates photographic recording.

Camera shake #

Unintended camera movement during an exposure, causing blur. It differs from subject movement, although both may appear in the same photograph.

Carbon print #

A pigment image held in hardened gelatin, traditionally transferred from sensitised tissue. Its image substance differs from the metallic silver of a gelatin silver print.

Carbon tissue #

A gelatin-and-pigment layer used in carbon-transfer printing. Light hardening and transfer establish the final image rather than conventional silver development on the final support.

Carte de visite #

A small photograph mounted on a visiting-card-sized card, widely collected and exchanged in the nineteenth century. Many examples are albumen prints.

Cassette #

A light-tight film container, such as the 135 cassette. Cartridge is also used, but particular cassette and cartridge systems have different loading and transport mechanisms.

Catadioptric lens #

A lens using both mirrors and refracting elements, commonly called a mirror lens. Many photographic examples have a fixed aperture and produce ring-shaped out-of-focus highlights.

Catchlight #

A visible reflection of a light source in a subject’s eye. Its position and shape can reveal the lighting arrangement.

CCD #

Charge-coupled device: an image-sensor technology that transfers charge through the device for readout. CCD construction alone does not guarantee a global shutter or a particular image character.

CdS meter #

An exposure meter using a cadmium sulphide light-dependent resistor. It requires electrical power and may respond slowly after a large change in illumination.

Cement separation #

Deterioration or detachment of the optical cement joining lens elements. It may appear as edge patterns, coloured fringes or milky areas and differs from ordinary internal dust.

Centre filter #

A graduated neutral-density filter darker at its centre, used to reduce illumination fall-off with certain wide-angle lenses. It requires exposure compensation.

Centre-weighted metering #

Metering that gives greater importance to the central region while considering a larger part of the frame. The weighting pattern varies by camera.

Changing bag #

A light-tight bag with arm sleeves for handling film without a darkroom. Loading a reel and freeing a jammed film are typical uses.

Characteristic curve #

A graph showing how a photographic material’s density changes with log exposure. Its toe, straight-line region and shoulder help describe tonal response.

Chemical fog #

Unwanted image density arising from chemical action rather than the intended exposure. Exhausted chemistry, contamination and processing conditions can contribute.

Chiaroscuro #

The use of strong light-and-dark relationships to model form or create atmosphere. The term comes from the visual arts and predates photography.

Chimping #

Informal DSLR-era slang for repeatedly checking photographs on the rear display. Reviewing a histogram or focus detail can be a deliberate technical check rather than a distraction.

Chromatic aberration #

Failure to bring different wavelengths into matching image positions or focus. It can appear as coloured fringes; lateral and longitudinal forms behave differently.

Chromatic focus shift #

Variation of best-focus position with wavelength. Infrared focusing marks on some lenses provide a correction for specified conditions, not a universal adjustment for every infrared material.

Chromogenic #

Describes a photographic process in which development forms image dyes. Colour-negative film, most colour print papers and some black-and-white films use this principle.

Circle of confusion #

The blur circle used as an acceptable-sharpness criterion in depth-of-field calculations. The acceptable size depends on enlargement, viewing distance and the required result.

Circular polariser #

A polarising filter combining a linear polariser with a quarter-wave plate. It is usually the appropriate type for cameras whose metering or autofocus systems are affected by linear polarisers.

CLA #

Clean, lubricate and adjust: a common description of camera servicing. The abbreviation does not specify which parts were inspected, replaced or calibrated.

Clipping #

Mapping values beyond a limit to that limit, losing distinctions in highlights, shadows or colour channels. Capture clipping and clipping introduced during editing are different problems.

Close-up lens #

An auxiliary positive lens fitted in front of a taking lens to allow closer focusing. Its strength is commonly stated in dioptres.

CMOS #

Complementary metal-oxide-semiconductor: the technology used for most later DSLR sensors. Noise, dynamic range and shutter behaviour depend on the particular sensor design, not just the CMOS label.

Coating separation #

Failure or change in a surface coating, sometimes loosely described in condition reports. It should be distinguished from cement separation between bonded lens elements.

Cold shoe #

An accessory mounting shoe without a built-in electrical flash-triggering contact. A mounted flash may still be triggered through a separate cable.

Collodion #

A solution that forms a thin film as its solvents evaporate. In wet-plate photography it binds the light-sensitive material to glass or a dark-coated metal support.

Collotype #

A photomechanical printing process using a treated gelatin surface to control ink acceptance. It can reproduce delicate tonal gradations without the regular halftone screen of many commercial prints.

Colour balance #

The relationship between colours in an image, especially whether neutral subjects appear neutral. Film choice, lighting, filters, processing and digital white balance can all affect it.

Colour coupler #

A chemical component that forms an image dye by reacting with products of colour development. In most chromogenic materials couplers are incorporated in the photographic layers.

Colour negative #

A film image with reversed tones and complementary colours, intended for printing or scanning. Most modern colour negatives have an orange mask that must be accounted for in reproduction.

Colour rendering index #

CRI: a measure of how a light source renders test colours relative to a reference source. A high number does not by itself describe every photographic colour-rendering issue.

Colour separation filter #

A filter used to isolate part of the spectrum for colour-separation photography. A set of filtered records can be combined to reproduce a colour image.

Colour space #

A defined system for representing colours, such as sRGB or Adobe RGB. Profiles and output conversion matter when images move between devices.

Colour temperature #

A description of a light source’s colour using kelvin, based on a reference radiator. Lower values look warmer; higher values look cooler, but the number does not fully describe a light’s spectrum.

Coma #

An off-axis aberration that makes a point of light look smeared or comet-shaped. It can be conspicuous in photographs of stars made at large apertures.

Combination printing #

Making a single print from more than one negative. It long predates digital compositing and can combine subjects, skies or other image elements.

Compact camera #

A relatively small camera with a built-in lens. The category includes simple film point-and-shoots and sophisticated digital models; compact does not specify sensor or film size.

CompactFlash #

A removable memory-card format used by many early and professional DSLRs. Type, capacity and interface compatibility must be checked against the camera manual.

Compensating developer #

A developer or development method that restrains highlight density relative to shadows. Its effect depends on formulation, dilution, agitation and exposure.

Compound lens #

A lens made from multiple optical elements. A compound shutter, by contrast, can refer to a particular historical pneumatic shutter design.

Compression #

Reducing the data needed to store a file, either losslessly or with information discarded. Optical perspective compression is an unrelated visual effect associated with distant viewpoints.

Condenser enlarger #

An enlarger using condenser lenses to direct light through the negative. Its printing character and visibility of dust can differ from those of a diffusion enlarger.

Contact print #

A print made with the negative placed directly against the printing material. It is approximately the same size as the negative.

Contact sheet #

A group of small positive images made by contact printing negatives, or a digital equivalent. It helps compare frames and record selections.

Continuous autofocus #

An autofocus mode that keeps updating focus while active, often labelled AF-C or AI Servo. Performance depends on the subject, lens, settings and camera.

Continuous light #

Illumination that remains on rather than firing briefly like flash. Tungsten lamps, fluorescent fixtures and LEDs can all provide it.

Contrast #

The separation between light and dark tones, either across the whole image or locally. A high-contrast scene can exceed the recording medium’s dynamic range.

Contrast-detection autofocus #

Focusing that evaluates image contrast and adjusts the lens towards a sharp result. Many DSLRs use it in live view even when their optical-finder autofocus uses phase detection.

Copy camera #

A camera arranged for photographing flat originals, often with careful alignment and controlled illumination. Process cameras are specialised examples used in reproduction work.

Correction lens #

An eyepiece lens that adjusts viewfinder focus for the photographer’s eyesight. It changes the finder view, not the taking lens‘s focus.

Coupled rangefinder #

A rangefinder mechanically linked to the taking lens‘s focusing mechanism. Aligning its images sets focus, provided the body and lens are correctly calibrated.

Crop factor #

The ratio between a reference format’s diagonal, usually 24 × 36 mm, and another format’s diagonal. It helps compare angle of view; it does not physically change lens focal length.

Cross processing #

Developing a photographic material in a process intended for another material, such as slide film in C-41. Colour, contrast and density may shift substantially.

Cross-type AF point #

A phase-detection autofocus point sensitive to detail in two orientations. Whether it operates as a cross-type point can depend on the fitted lens and maximum aperture.

Curtain shutter #

A shutter using flexible curtains, commonly moving across the focal plane. Curtain material, travel direction and timing vary across camera generations.

Curvature of field #

An aberration in which the sharpest image lies on a curved surface rather than a plane. Focusing the centre and edges together can therefore be difficult.

Cyanotype #

An iron-based photographic process producing a characteristic blue image. It can make contact prints or photograms without a silver-based emulsion.

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D

Daguerreotype #

An early direct-positive photographic object on silver-coated copper. Its reflective image changes appearance with viewing angle and is vulnerable to damage.

Daguerreotype case #

A protective enclosure for a daguerreotype‘s plate, cover glass and mount. A similar case may hold an ambrotype, so the enclosure alone does not identify the process.

Dark bag #

Another name for a Changing bag, used for light-sensitive handling when a suitable darkroom is unavailable.

Dark cloth #

An opaque cloth placed over a photographer’s head and a view camera‘s rear to shade the ground glass. It improves visibility for composition and focusing.

Dark frame #

An exposure made without scene light, used to study or compensate for some sensor-related artefacts. It cannot remove the random photon noise of the original light exposure.

Dark slide #

An opaque sliding cover protecting film or plates in a holder or back. It must be withdrawn for exposure and replaced before removing the holder.

Darkroom #

A space with controlled light for handling and processing photographic materials. Safelight suitability depends on the material; some tasks require complete darkness.

Data back #

A camera back that records information, often the date, onto film. More elaborate backs can provide interval timing or exposure information.

Daylight-balanced film #

Colour film designed to give its intended colour balance under a specified daylight-like source. Tungsten lighting generally requires filtration or a deliberate colour shift.

Dedicated flash #

A flash designed to communicate with a particular camera system. Shoe fit alone does not establish TTL compatibility, safe trigger voltage or full functionality.

Deep focus #

An image treatment in which subjects across a substantial distance range appear sharp. Small apertures, shorter focal lengths and careful focus placement can help achieve it.

Demosaicing #

Reconstructing a full-colour digital image from samples recorded through a sensor’s colour-filter array. Different algorithms balance detail, noise and false-colour artefacts differently.

Densitometer #

An instrument measuring optical density in film or prints. Transmission and reflection densitometers are used for different materials.

Density #

A logarithmic measure of how strongly a material blocks or reflects light. A denser negative transmits less light to the printing paper or scanner.

Depth of field #

The range of subject distances judged acceptably sharp at a given focus setting. Aperture, magnification, format, output size and viewing conditions affect the judgement.

Depth of focus #

The tolerance for displacement of the image plane behind a lens while retaining acceptable sharpness. It is different from depth of field in subject space.

Depth scale #

Lens markings indicating approximate near and far depth-of-field limits for selected apertures. Their acceptable-blur assumptions may be too generous for large enlargements.

Depth-of-field preview #

A control that closes the diaphragm to the selected aperture for inspection through an optical finder. The view becomes darker as the aperture closes.

Developer #

Chemistry that converts an exposed latent image into a visible image. The formulation and process determine which material it can develop and how it behaves.

Developer exhaustion #

Loss of a developer‘s useful activity through use, oxidation or contamination. Capacity, storage and replenishment instructions determine when it should be replaced.

Developing-out paper #

Photographic paper that receives a brief exposure to form a latent image, then develops chemically. It contrasts with printing-out paper, whose image forms visibly during exposure.

Development #

The stage that makes a latent photographic image visible, or the processing of raw digital data into a viewable image. The chemical and digital uses describe different mechanisms.

Diaphragm #

The mechanism controlling the lens opening. An iris uses overlapping blades; some early lenses use fixed openings, rotating discs or Waterhouse stops.

Dichroic head #

An enlarger head with adjustable colour filtration. It can balance colour prints or control contrast with suitable variable-contrast black-and-white paper.

Diffraction #

The spreading of light at an opening. At small apertures it limits fine-detail sharpness even with a well-corrected lens.

Diffuser #

Material or a device that scatters light. Softness depends largely on the apparent size of the light source as seen from the subject, not merely the presence of a diffuser.

Diffusion enlarger #

An enlarger that illuminates the negative with diffuse light. It commonly renders dust and small surface marks less harshly than a condenser arrangement.

Digital back #

A sensor-based recording unit fitted to a compatible camera in place of a film back. Mount, trigger, power and software compatibility all matter.

Digital ICE #

An infrared-assisted dust and scratch detection technology used in some scanners. Conventional silver black-and-white films and certain other materials can interfere with infrared correction.

Digital negative #

Either a raw digital capture in broad usage, or a digitally produced transparency used for contact printing. DNG is a particular raw-file format, not the sole meaning of the phrase.

Digital zoom #

Cropping and enlarging an image electronically to give tighter framing. It does not provide the same additional subject detail as using a suitable longer optical focal length.

DIN #

A logarithmic film-speed scale. An increase of 3° represents approximately twice the speed; ISO 100/21° combines arithmetic and logarithmic ratings.

Dioptre #

A unit of optical power equal to the reciprocal of focal length in metres. Close-up attachments and viewfinder correction lenses commonly use it.

Direct flash #

Flash aimed straight at the subject without bouncing from another surface. Its shadows and reflections differ from bounced or off-camera lighting.

Direct positive #

A positive image formed without making a separate negative for subsequent printing. Daguerreotypes and certain papers are examples, although their mechanisms differ.

Disc film #

A consumer film system with small frames arranged around a flat disc inside a cartridge. It is unrelated to optical discs and digital storage.

Distortion #

A change in image geometry, such as barrel or pincushion distortion. It differs from perspective, which is determined by viewpoint.

DNG #

Digital Negative: a documented raw-image container format developed by Adobe. Converting to DNG does not guarantee preservation of every proprietary feature or item of metadata.

Dodging #

Reducing exposure to a selected part of a darkroom print to keep it lighter. Digital dodging tools similarly lighten chosen areas.

Double exposure #

Two exposures recorded on the same frame or combined to resemble that result. Film cameras may offer a multiple-exposure control to avoid advancing the film.

Double extension #

A camera’s ability to extend the lens approximately twice its focal length from the image plane. With a simple lens, that permits roughly life-size reproduction.

Doublet #

A lens group made from two elements, cemented together or separated by air. Different doublet designs correct different combinations of aberrations.

DPI #

Dots per inch: primarily a printer or marking-device measure. It is often confused with image pixels per inch, but a printer can use several ink dots to reproduce one image pixel.

Drop bed #

A folding-camera bed that can be lowered beyond its normal position, often to keep it out of a wide-angle lens‘s field. Supported focusing and movements depend on the design.

Dry mounting #

Attaching a print to a support with heat-activated adhesive tissue or a related process. It can flatten a print but affects reversibility and conservation choices.

Dry plate #

A sensitised photographic plate that can be stored and exposed dry. Gelatin dry plates removed the need to prepare and develop each plate while wet.

Dry plate camera #

A camera designed for ready-sensitised dry plates. Plate dimensions, holder fit and image-plane registration must all match, even where nominal format names agree.

DSLR #

Digital single-lens reflex camera: a digital camera whose reflex viewing system shows the taking lens‘s image through an optical finder. During normal exposure the mirror moves out of the light path.

Dual card slots #

Two memory-card slots in one camera, with options that may include backup, overflow or separating file types. Two slots do not automatically mean every photograph is duplicated.

Duotone #

A reproduction made using two inks or colour components to shape tone and colour. It differs from a conventional neutral black-and-white print.

Duplex loading #

Loading two sheets or plates in a double-sided holder, one on each face. Each side normally has its own dark slide and exposure identification.

DX coding #

Machine-readable coding on 35 mm film cassettes, commonly used to set film speed automatically. Other parts of the DX system encode additional information.

Dynamic range #

The span between the darkest and brightest signals a system can usefully record or reproduce. The result depends on the noise threshold and measurement method, not just bit depth.

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E

E-6 #

A standard processing sequence for many colour reversal films, producing transparencies. Not all historical slide films use E-6.

Easel #

An enlarging accessory that holds paper flat and defines print borders. Adjustable blades allow different image sizes and margins.

ED glass #

Extra-low-dispersion glass used to help control chromatic aberration. ED and similar markings describe optical material or design features, not a complete measure of lens quality.

EF mount #

Canon’s electronically controlled EOS lens mount used by its autofocus film SLRs and many DSLRs. EF-S and later RF lenses have different compatibility restrictions; an EOS name alone is insufficient.

EF-S #

Canon’s lens specification for compatible APS-C EOS DSLR bodies. EF-S lenses are not intended to mount on Canon full-frame or APS-H DSLRs.

Effective aperture #

The working f-number after allowing for factors such as close-focus extension. It can be smaller in light-gathering terms than the nominal aperture marked on the lens.

Electronic first-curtain shutter #

EFCS: exposure begins electronically and ends with a mechanical curtain. Some DSLRs offer it in particular modes to reduce vibration; limits vary by camera.

Electronic flash #

A light source producing a short burst by discharging stored electrical energy, usually through a xenon tube. Power setting affects flash duration differently across designs.

Electronic shutter #

Exposure timing controlled electronically at the sensor, rather than solely by moving shutter curtains. Some DSLRs provide electronic functions only in live view or particular modes.

Emulsion #

The light-sensitive coating of a photographic material, usually silver halides held in gelatin. Film can contain several emulsion layers and additional functional layers.

Enlarger #

A darkroom projector that forms an image of a negative or transparency on sensitised paper. Lens choice, alignment and illumination affect the print.

Entrance pupil #

The apparent image of the aperture stop viewed through the front of a lens. Its diameter defines the f-number, and its location matters for parallax-free panorama rotation.

Equivalent focal length #

A focal length stated relative to another format to compare angle of view. A 50 mm-equivalent lens does not necessarily have an actual focal length of 50 mm.

EV #

Exposure value: a number representing combinations of aperture and shutter speed. At a fixed ISO, a change of one EV corresponds to a doubling or halving of exposure.

Evaluative metering #

Multi-area metering that uses an algorithm to assess the scene and recommend exposure. Names such as matrix and multi-segment describe related approaches with maker-specific behaviour.

EXIF #

Exchangeable Image File Format metadata, commonly containing exposure settings, camera identification and capture time. Metadata can be absent, edited or stripped and is not proof of authenticity.

Exit pupil #

The apparent image of the aperture stop viewed through the rear of a lens. Its position affects how rays reach the image plane and related optical calculations.

Exposure #

The amount of light reaching the recording surface over time. In ordinary camera operation it is controlled by aperture, shutter duration and scene illumination; ISO influences metering and digital signal handling.

Exposure compensation #

An instruction to an automatic exposure system to render brighter or darker than its metered recommendation. Positive compensation generally increases exposure, subject to the camera’s operating limits.

Exposure index #

EI: the speed rating chosen by the photographer for metering a film. It may differ from the manufacturer’s ISO rating to suit processing, equipment or the intended tonal result.

Exposure latitude #

The range of exposure variation over which a material can still deliver an acceptable result. It is related to, but different from, dynamic range.

Exposure triangle #

A teaching model connecting aperture, shutter speed and ISO. Physically, ISO does not admit more light: aperture and duration govern exposure for a given scene illumination.

Extension tube #

A hollow spacer between a lens and body that allows closer focusing. It generally sacrifices distant focus and may affect automatic aperture and electronic functions.

Eye relief #

The distance from a finder eyepiece at which the full viewing field can be seen. Generous eye relief helps photographers who wear spectacles.

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F

F mount #

Nikon’s long-running bayonet mount used across many film SLR and DSLR generations. Mechanical fit does not guarantee safe mounting, metering, aperture control or autofocus.

F-number #

Focal length divided by entrance-pupil diameter. Smaller f-numbers indicate larger relative apertures; adjacent full stops differ by approximately the square root of two.

Fast lens #

A lens with a large maximum relative aperture, such as f/1.4 or f/2. It permits shorter exposures in a given light but does not necessarily focus faster.

FD mount #

Canon’s manual-focus SLR lens system preceding EF. FD lenses do not mount directly on an EF body, and adaptation introduces focus and functional limitations.

Ferrotype #

Another name for a tintype. The support is iron, despite the familiar tin-based name.

Fibre-based paper #

Photographic paper whose support is paper fibre rather than a plastic-coated paper base. It usually needs more washing and more careful drying than resin-coated paper.

Field camera #

A portable view camera, often with a folding bed. It typically offers fewer or more restricted movements than a studio monorail camera.

Field of view #

The extent of the scene recorded. It may be expressed as an angle or as subject dimensions at a stated distance.

Fill flash #

Flash used to lift shadows or adjust the relationship between a subject and ambient light. It need not be the dominant illumination.

Film base #

The transparent or translucent support carrying the photographic layers. Historical nitrate, acetate and polyester bases have different handling and preservation characteristics.

Film flatness #

How consistently film lies in the intended image plane. Pressure plates, vacuum backs, film holders and film curl can affect it.

Film gate #

The opening that defines the exposed frame in a film camera. Dirt or damage here can mark film or intrude into the image.

Film holder #

A light-tight holder positioning a sheet or plate at the camera’s image plane. The holder’s type, dimensions and registration must match the camera.

Film leader #

The leading portion of film used for loading and transport. On 35 mm film it is often cut to a narrower tongue.

Film pack #

A light-tight pack of individual sheets arranged for sequential exposure in a compatible holder. Historical film packs differ from ordinary roll-film cartridges and modern sheet-film boxes.

Film plane #

The surface where film is positioned for exposure. A mark resembling a circle crossed by a line identifies its location on many camera bodies.

Film speed #

A standardised measure of a film’s response to light under specified conditions. A higher rating generally permits less exposure, with trade-offs that depend on the emulsion.

Filter factor #

The exposure multiplier required for a filter under specified conditions. A factor of 2 corresponds to one stop; actual compensation can depend on the light spectrum and recording material.

Finder #

The viewing device used to compose or focus. Optical, reflex, waist-level, sports and electronic finders present different information and limitations.

Fine grain #

A description of film or development producing a relatively unobtrusive grain pattern. It does not guarantee high resolution or high acutance.

Firmware #

Software stored within a camera or accessory that controls its operation. Updates must match the exact model and follow the manufacturer’s power and installation instructions.

Fisheye #

An extremely wide-angle lens that deliberately uses a non-rectilinear projection. Straight lines away from the image centre commonly appear curved.

Fixer #

Chemistry that removes remaining undeveloped silver halides and makes the processed image substantially insensitive to further exposure. Fixing does not replace adequate washing.

Flag #

An opaque screen used to block light from part of a scene or keep unwanted light off a lens. It can control spill without changing the lamp itself.

Flange focal distance #

The specified distance from a lens mount‘s reference flange to the image plane. It is important for lens adaptation and accurate infinity focus.

Flare #

Unwanted light scattered or reflected within a lens or camera. It can lower contrast across the image or create visible shapes and ghosts.

Flash bulb #

A single-use light source producing a flash by burning material within a glass envelope. Its timing and ignition requirements differ from electronic flash.

Flash cube #

A rotating package of four single-use flash bulbs. Electrically fired cubes and mechanically fired Magicubes require different triggering systems.

Flash duration #

The length of the light pulse, measured using a stated intensity threshold such as t.1 or t.5. It can govern motion freezing when flash dominates the exposure.

Flash exposure compensation #

A control that raises or lowers automatic flash output relative to the flash system’s recommendation. It can be independent of ambient exposure compensation.

Flash powder #

An early flash illumination method based on a rapidly burning mixture. It belongs to the history of photography rather than routine modern camera operation.

Flash synchronisation #

Coordination of flash output with the shutter‘s open interval. Incorrect timing can produce partial illumination or a dark band.

Flashmatic #

A distance-linked automatic flash-exposure arrangement, often setting aperture from focus distance and flash guide number. It differs from a system that meters flash reflected from the subject.

Floating element #

A lens group that changes position relative to other groups during focusing to preserve correction. It is especially useful in lenses designed for close distances.

Focal length #

The optical distance from a lens’s rear principal plane to the image plane when focused at infinity. It affects image scale and angle of view for a given format.

Focal reducer #

An optical adapter that reduces effective focal length and image-circle size. It may increase image-plane illumination, but fit and mirror clearance are critical and most modern examples target mirrorless bodies.

Focal-plane shutter #

A shutter close to the film or sensor, usually using moving curtains or blades. At fast speeds a slit travels across the frame, limiting normal flash synchronisation.

Focus breathing #

A change in angle of view as focus distance changes. It can matter when framing close-ups, stacking images or recording video with a DSLR.

Focus confirmation #

An indicator showing that the camera judges focus to be achieved. Its tolerance and accuracy may differ from what is needed for a large print or a very wide aperture.

Focus shift #

Movement of the best-focus position when aperture changes, often associated with residual spherical aberration. It is different from an incorrectly calibrated autofocus system.

Focus stacking #

Combining photographs focused at different distances to extend the apparent sharp region. Subject movement and changing magnification can create alignment artefacts.

Focusing cloth #

Another name for a dark cloth, used to shade a view camera‘s focusing screen.

Focusing screen #

A surface on which the lens forms a visible image for focusing, particularly in reflex and view cameras. Its texture and optical aids affect ease of use.

Fog #

Unwanted density in film or paper, caused by factors including stray light, age, heat, radiation or chemistry. It reduces useful separation between image tones.

Folding camera #

A camera that collapses for storage, usually using bellows and a hinged bed or front assembly. Check bellows condition and locking mechanisms before use.

Format #

The dimensions or class of the recorded image, such as 35 mm, medium format or large format. For digital files, format can instead mean the file structure, such as JPEG or TIFF.

Four Thirds #

A DSLR system built around a sensor approximately 17.3 × 13 mm with a 4:3 aspect ratio. It is distinct from the later Micro Four Thirds mirrorless system.

Foveon sensor #

A sensor design using stacked light-sensitive layers to distinguish colour at each spatial location. It differs from the more common surface colour-filter mosaic used by most DSLRs.

FP flash #

Historically, a long-burning focal-plane flash bulb for slit shutters. Later FP or high-speed sync uses repeated electronic pulses; the two technologies are different.

Frame counter #

A display indicating the number of exposures made or remaining. Mechanical counters may need manual resetting, while electronic estimates depend on the camera and medium.

Frame rate #

The number of frames recorded per second in a burst or moving-image sequence. It does not indicate how many frames can be sustained before the buffer fills.

Fresnel screen #

A screen with fine concentric optical grooves that redirects light to improve viewing brightness. In a view camera its position relative to the ground glass must follow the manufacturer’s design.

Front cell focusing #

Focusing by moving a lens’s front group rather than the complete optical assembly. It is common on some older folding and simple cameras.

Front standard #

The part of a view camera that carries the lens board. Its rise, shift, tilt and swing provide framing and focus-plane controls.

Front-curtain sync #

Flash firing near the beginning of an exposure. Moving subjects lit by both ambient light and flash can show a trail extending ahead of the flash-frozen position.

Full frame #

In DSLR usage, a sensor approximately 24 × 36 mm, matching the common 35 mm still frame. Elsewhere the phrase may simply mean the entire uncropped frame.

Fungus #

Fungal growth that may develop on optical surfaces under favourable storage conditions. Cleaning can remove growth, but etched coatings or glass may remain damaged.

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G

Gamma #

A measure or description of tonal response, used differently in sensitometry and digital encoding. In film work it commonly relates to the slope of part of the characteristic curve.

Gelatin silver print #

A black-and-white photographic print whose silver image is held in a gelatin binder. It became a principal twentieth-century photographic printing method.

Ghosting #

A secondary image or shape, often produced by internal optical reflections. The word can also describe motion artefacts in HDR composites and other multi-image techniques.

Glass plate #

A glass support carrying a photographic image layer. It may be a negative, transparency or direct-positive object depending on the process.

Global shutter #

Exposure timing in which the image area is sampled over the same interval, avoiding row-by-row timing differences. It is a shutter characteristic, not a synonym for CCD.

Golden hour #

A loose term for low-angle sunlight around sunrise or sunset. Its duration and colour depend on latitude, season, weather and local geography.

Graded paper #

Black-and-white printing paper manufactured with a fixed contrast grade. Changing print contrast normally requires another grade or a change in processing.

Graduated filter #

A filter whose strength varies across its surface. A graduated neutral-density filter can reduce brightness differences between a sky and foreground.

Grain #

The visible granular structure of a photographic image, especially when film is enlarged. The appearance relates to developed image material and differs from a simple map of individual original crystals.

Grain focuser #

An enlarging aid that magnifies the projected negative so its grain or fine structure can be focused sharply at the paper plane.

Grey card #

A reference target with a specified neutral reflectance, used for exposure or colour-balance checks. Its angle and illumination affect the reading.

Ground glass #

A translucent focusing surface on which a lens forms an image. In a view camera the image is typically upside down and laterally reversed.

Guide number #

A flash-output rating: at a stated ISO and coverage, guide number equals aperture f-number multiplied by flash-to-subject distance. Units and zoom-head position must match the specification.

Gum bichromate #

A pigment printing process using a light-hardened gum binder, traditionally sensitised with dichromate. Several layers can build colour and tonal effects.

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H

Halation #

A halo or spreading glow around bright areas caused by light scattering or reflecting within photographic material. Anti-halation layers are intended to reduce it.

Half-frame #

Usually a 35 mm still-camera format making approximately 18 × 24 mm images. It gives about twice as many exposures as 24 × 36 mm on the same film length.

Halftone #

A printed reproduction that simulates continuous tones through a pattern of dots or other marks. It is distinct from a continuous-tone photographic print.

Hand colouring #

Adding colour manually to a photographic image. It is a colouring technique, not evidence that the original camera recorded colour.

Hard light #

Light producing relatively well-defined shadow edges, usually from a source small in angular size at the subject. Distance and source size both affect it.

Haze #

A cloudy reduction in optical clarity caused by deposits, degraded materials or other changes. It can reduce contrast and increase flare even when individual dust particles are not obvious.

HDR #

High dynamic range: a recording or processing approach accommodating a wide brightness range, often by combining bracketed exposures. HDR is not synonymous with exaggerated colour or halos.

Heliography #

A name associated with Niépce’s early light-based image-making experiments, including light-hardened bitumen. It belongs to the experimental beginnings of permanent photography.

High key #

An image treatment dominated by light tones. It can retain controlled shadows and full detail rather than simply being overexposed.

High-speed sync #

Electronic flash operation that provides illumination while a focal-plane shutter‘s slit crosses the frame at speeds above normal sync. Effective output and working distance are reduced.

Histogram #

A graph showing the distribution of image brightness or colour-channel values. A camera’s histogram is commonly based on its processed preview rather than directly on unprocessed raw data.

Hot pixel #

A sensor pixel that appears unusually bright under particular conditions, often in long exposures. It differs from a permanently dead pixel and from ordinary random noise.

Hot shoe #

An accessory shoe with electrical contacts, commonly used to mount and trigger flash. Additional contacts and protocols are system-specific.

Hot spot #

A local area of unusually high brightness, such as a reflection from a light source. In infrared photography, a lens can also produce a central bright patch through internal reflections.

Hybrid autofocus #

An autofocus arrangement combining methods, commonly phase and contrast detection. Some later DSLRs use sensor-based hybrid systems in live view.

Hyperfocal distance #

A calculated focus distance that places the far depth-of-field limit at infinity for a chosen aperture and acceptable blur criterion. Infinity at that limit is not rendered as sharply as the exact focus plane.

Hypo #

A traditional name for sodium thiosulphate and, more loosely, photographic fixer. Not every fixer uses sodium thiosulphate as its active fixing agent.

Hypo clearing agent #

A wash aid that helps remove residual fixer components from suitable photographic materials. It does not replace fixing or the specified final wash.

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I

ICC profile #

A description used by colour-management systems to interpret a device’s or colour space‘s values. Assigning a profile and converting between profiles perform different operations.

Image circle #

The circular area a lens projects at the image plane with usable illumination or quality. Camera movements require coverage beyond the frame’s normal corners.

Image stabilisation #

A system that compensates for camera movement using lens elements, a moving sensor or other methods. It does not freeze movement of the subject.

Image stabiliser switch #

A control enabling or selecting a lens or body’s stabilisation mode. Tripod use and panning instructions depend on the particular system.

Incident metering #

Measuring light falling onto the subject rather than light reflected from it. The meter position and receptor direction should suit the intended lighting measurement.

Infinity #

A focusing setting for sufficiently distant subjects that incoming rays can be treated as parallel. The marked stop may not be exact after repair, adaptation or temperature changes.

Infrared photography #

Photography using sensitivity beyond the visible red end of the spectrum. Film, filters, focusing corrections and digital-camera modifications require material-specific handling.

Instant film #

A material system that incorporates chemistry to produce a photograph shortly after exposure. Integral and peel-apart materials differ in construction and handling.

Integral film #

Instant film in which the image and processing layers remain within a single finished unit. It differs from peel-apart material that requires separation after processing.

Interchangeable lens #

A lens designed to be removed and replaced through a camera’s mount. Not all removable lens cells are intended as routine interchangeable-lens systems.

Internal focusing #

Focusing by moving internal lens groups rather than the entire lens assembly. The lens’s outer length may remain unchanged, while its effective focal length can vary.

Intervalometer #

A device or built-in function that triggers exposures at set intervals. It is used for time-lapse sequences, monitoring and repeated long exposures.

Inverted telephoto #

Another name for a retrofocus lens: a wide-angle design with extended clearance behind the lens for mechanisms such as an SLR mirror.

Iris #

A diaphragm with overlapping blades that vary the lens opening. Blade number and shape influence the appearance of stopped-down highlights and diffraction stars.

ISO #

A standards designation used for film-speed ratings and digital-camera sensitivity settings. Raising digital ISO does not make the sensor receive more light; it changes signal handling and the exposure the meter recommends.

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J

JPEG #

A widely used processed-image format, usually using lossy compression. Camera JPEGs incorporate choices such as white balance, tone curve, sharpening and noise reduction.

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K

Kelvin #

The unit used for colour-temperature settings, written K. It describes one aspect of light colour rather than the complete spectral distribution.

Key light #

The main light shaping a subject. Fill, rim and background lights are described in relation to its role.

Kodachrome #

A family of colour reversal films whose specialised processing introduced the image dyes. It does not use the E-6 process used by many later slide films.

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L

Large format #

Photography using large sheets or plates, commonly 4 × 5 inches and above. Definitions vary, but the term usually implies individual sheet handling and often a view camera.

Latent image #

The invisible image change formed by exposure in a photographic material before development. Storage conditions and delay before processing can affect it.

Latitude #

Shorthand for exposure latitude: the tolerance for exposure variation while retaining a usable result. Negative and reversal materials often behave differently.

Leaf shutter #

A shutter using overlapping blades, commonly within a lens. Many can synchronise electronic flash at all marked speeds, subject to the particular shutter and flash combination.

Lens board #

A removable plate used to mount a lens and often its shutter to a view camera. Size, light trap and hole dimensions must suit the equipment.

Lens cap exposure #

An exposure timed by removing and replacing the lens cap, historically used when exposure times were long enough. It is unsuitable for precise short timing.

Lens hood #

A shade that reduces unwanted light reaching the lens front. A hood designed for the wrong angle of view can intrude into the photograph.

Lens mount #

The mechanical interface attaching lens and camera, sometimes with electrical or mechanical couplings. A shared brand does not guarantee a shared mount or full compatibility.

Light leak #

Unintended light entering a camera, film holder or processing container. Worn seals, pinholes and poor assembly can create characteristic fogging patterns.

Light meter #

An instrument estimating exposure from measured light. Reflective and incident meters measure different things and require different interpretation.

Light seal #

A strip, gasket, labyrinth or other barrier that prevents stray light entering equipment. Ageing foam can become sticky, crumble or fail.

Light value #

LV: a lighting-level notation sometimes used with exposure tables and meters. Its relationship to EV depends on the convention and reference ISO being used.

Line pairs per millimetre #

A resolution measure describing pairs of alternating light and dark lines per millimetre. Results depend on contrast, test method and where in the image they are measured.

Linear polariser #

A filter transmitting light of a selected linear polarisation. It can interfere with some camera metering and autofocus systems, which is one reason circular polarisers are used.

Lith printing #

A darkroom printing method using suitable papers and highly diluted lith developer to produce distinctive tones and grain-like texture. Exposure and development interact strongly.

Live view #

Viewing a continuous image from the main sensor on a screen. In a DSLR the mirror is normally raised, changing optical-finder availability and often autofocus behaviour.

Long exposure #

An exposure long enough for movement, camera stability, heating or reciprocity effects to become relevant. There is no single shutter duration that defines it.

Long-exposure noise reduction #

A digital-camera function that commonly records a second dark exposure to identify some fixed-pattern noise and hot pixels. It can occupy the camera for roughly another exposure-length interval.

Lossless compression #

File compression designed to permit exact reconstruction of the encoded data. It reduces storage requirements without the intentional data discard of lossy compression.

Lossy compression #

Compression that discards information to reduce file size. Repeated editing and resaving in a lossy format can accumulate artefacts.

Loupe #

A small magnifier used to inspect a ground glass, negative, slide or print. Ground-glass focusing requires the magnifier to be set to the correct screen surface.

Low key #

An image treatment dominated by dark tones, usually with controlled highlights. It need not be underexposed or lack shadow detail.

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M

M sync #

Flash synchronisation timed to allow a medium-peak flash bulb to reach useful brightness. It generally fires earlier than X sync for electronic flash.

M42 mount #

A screw lens mount usually using a 42 mm-diameter, 1 mm-pitch thread for still-camera lenses. Automatic diaphragm pins and open-aperture metering couplings vary across implementations.

Macro #

Close-up photography at substantial reproduction ratios; 1:1 means a subject is recorded life-size on the film or sensor. Marketing use of macro can include much lower magnifications.

Magnification #

The ratio of recorded image size to actual subject size, or the enlargement used for viewing or printing. State which meaning is intended.

Manual exposure #

Exposure control in which the photographer selects aperture and shutter speed. If Auto ISO remains enabled on a digital camera, the camera may still vary its sensitivity setting automatically.

Manual focus #

Focusing by the photographer rather than an autofocus system. It may use a distance scale, rangefinder, screen or magnified live view.

Masking #

Blocking or modifying selected image areas during exposure, printing or editing. It can be physical, photographic or digital.

Mat #

A cut mounting board surrounding a print, also called a window mount. It can separate the image from glazing and define its presentation.

Match-needle metering #

An exposure display in which the photographer aligns an indicator with a meter needle or reference mark. It is common on manual-exposure cameras.

Matt screen #

A textured focusing surface that makes the lens image visible. Its brightness and focusing precision depend on construction and the lens’s aperture.

Maximum aperture #

The largest opening a lens provides, expressed by its smallest f-number. Some zoom lenses have a maximum aperture that becomes smaller towards the long end.

Medium format #

A camera format larger than common 35 mm but generally smaller than conventional large format. Film examples often use 120 or 220; digital medium format covers several sensor sizes.

Megapixel #

One million image pixels. Pixel count alone does not describe lens performance, dynamic range, noise, colour accuracy or usable print detail.

Mercury battery #

A historical battery type used in some exposure meters and cameras. Its voltage behaviour differs from many replacements, so substitution can affect meter accuracy.

Meter coupling #

A mechanical or electronic link communicating settings such as aperture to a meter. A lens may mount physically while lacking the coupling needed for accurate open-aperture metering.

Metering mode #

The pattern and method by which a camera measures scene brightness. Spot, centre-weighted and multi-area modes can recommend different exposures for the same scene.

Microdrive #

A miniature hard disk made in a CompactFlash-compatible form, used by some early digital cameras. Power needs, physical fit and camera support differ from solid-state cards.

Microprism #

A focusing-screen aid made from tiny prisms that shimmer or break up an out-of-focus image. It can darken or become difficult to use with slower lenses.

Mirror blackout #

The loss of the optical finder image while an SLR mirror is raised. The duration affects the photographer’s ability to follow a moving subject.

Mirror lens #

Another name for a catadioptric photographic lens. It uses mirrors to fold the light path and reduce physical length.

Mirror lock-up #

Raising and holding an SLR mirror before exposure to reduce vibration or permit particular operations. Sensor-cleaning lock-up is a separate function on many DSLRs.

Mirror slap #

Vibration caused by movement of an SLR’s reflex mirror. It can reduce sharpness at susceptible shutter speeds even on a tripod.

Mirrorless #

A useful boundary term here: an interchangeable-lens digital camera without a DSLR’s reflex viewing mirror. Such cameras overlapped with DSLRs; the eras do not have a single clean dividing date.

Modelling light #

A continuous lamp in or near a flash head that helps preview direction and shadows. It does not necessarily match the flash’s colour or exact exposure balance.

Moiré #

A false repeating pattern caused by interference between fine scene detail and a sampling structure. Fabrics and screens are common triggers in digital photography.

Monobloc #

A studio flash unit containing its flash tube, controls and power electronics in one housing. It differs from a head powered by a separate pack.

Monochrome #

An image using one colour family or a single channel of tonal information. Black-and-white photography is one form, but monochrome can also be tinted.

Monorail camera #

A view camera whose standards move along a rail. It commonly offers extensive movements and extension at the cost of bulk.

Motor drive #

A powered mechanism that advances film and may also cock the shutter or rewind. A winder often offers a lower continuous rate, although manufacturers’ naming varies.

Movements #

View-camera adjustments such as rise, fall, shift, tilt and swing. They control framing, focus-plane orientation and image geometry in ways unavailable to a fixed camera body.

MTF #

Modulation transfer function: a description of how an imaging system transfers contrast at different spatial frequencies. Reading a chart requires knowing its test conditions and whether it is measured or calculated.

Multiple exposure #

More than one exposure combined in a single frame. Some cameras allow exposure compensation or blending options, while mechanical cameras may simply prevent film advance.

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N

Negative #

An image with brightness relationships reversed relative to the subject. A colour negative also has complementary colour relationships and commonly an orange mask.

Neutral-density filter #

A filter intended to reduce light without changing colour balance. It allows longer exposures or wider apertures; strong filters can still produce colour shifts.

Newton rings #

Interference patterns caused when smooth surfaces are separated by a very small, uneven gap. They can appear when film contacts glass during scanning or printing.

Nitrate film #

Film with a cellulose nitrate base. Its serious fire and deterioration characteristics distinguish it from later safety film and call for specialist collection handling.

Nodal point #

One of a lens’s cardinal optical points. The no-parallax rotation point used for panorama stitching is usually associated with the entrance pupil and should not automatically be called the nodal point.

Noise #

Unwanted variation in a digital image, seen as luminance or colour irregularity. Photon statistics, electronic readout and processing all contribute.

Normal lens #

A lens with an angle of view regarded as ordinary for its format, often with focal length near the frame diagonal. Around 50 mm is conventional for 24 × 36 mm cameras.

Notch code #

Edge notches identifying sheet-film type and helping determine emulsion orientation. Read the maker’s code rather than assuming all films use the same pattern.

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O

Off-camera flash #

Flash positioned away from the camera and triggered by cable, optical signal or radio. It allows lighting direction to be chosen independently of camera position.

Off-the-film metering #

OTF metering: measuring light reflected from the film surface during exposure, used by some film-era exposure and TTL flash systems. DSLR pre-flash metering is a different arrangement.

One-shot autofocus #

Autofocus that acquires focus and then holds it, generally for a stationary subject. Common labels include AF-S and One Shot AF.

Open-aperture metering #

Metering with the diaphragm fully open while the camera compensates for the selected taking aperture. It requires the appropriate information or mechanical coupling.

Optical brightener #

A substance that absorbs ultraviolet energy and emits visible light to make paper appear whiter. It can affect perceived colour under different illumination.

Optical slave #

A flash trigger responding to another flash’s light. A simple slave may fire on a metering pre-flash unless it supports the required sequence.

Optical viewfinder #

A finder presenting an optical view rather than an electronic display. It may look through the taking lens or through a separate viewing path.

Orange mask #

The orange-coloured mask of many colour-negative films, used to improve colour reproduction by compensating for unwanted dye absorptions. Scanning requires appropriate inversion and colour correction.

Orthochromatic #

Describes a material sensitive to blue and usually green light but not appreciably to red. Red subjects can reproduce dark; safelight use still depends on the particular product.

Overexposure #

More exposure than intended or appropriate for the desired result. Its consequences depend on whether the medium is negative film, reversal film or a digital sensor.

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P

Panchromatic #

Describes black-and-white material sensitive across the visible spectrum, although not equally to all wavelengths. It normally requires handling in complete darkness unless specific instructions permit otherwise.

Panning #

Moving the camera to follow a subject during exposure. It can keep the subject comparatively sharp while blurring the background into streaks.

Panoramic camera #

A camera recording a wide scene using a broad frame, rotating body, swinging lens or another specialised arrangement. Different designs produce different projections.

Paper negative #

A photographic negative formed on a paper support. Its fibres and translucency influence the appearance and sharpness of prints made from it.

Parallax #

A difference in viewpoint between separate viewing and taking paths. It affects close-range framing in many rangefinder, twin-lens and simple viewfinder cameras.

Parfocal #

Describes a lens that holds focus as focal length changes. Many still-photography zooms require refocusing even if they appear close to parfocal in ordinary use.

PC sync #

A flash synchronisation connector named for Prontor-Compur. It is unrelated to personal-computer interfaces.

Peel-apart film #

Instant material whose layers are separated after the specified development interval. It differs from integral instant film, which remains a single unit.

Pellicle mirror #

A thin, partly transmitting mirror that splits light between viewing and recording paths without swinging out of the way. It sacrifices some light and is delicate.

Pentamirror #

A lightweight arrangement of mirrors that erects the image for an SLR eye-level finder. It serves a similar purpose to a pentaprism but uses a different construction.

Pentaprism #

A five-sided prism used in many SLR finders to provide an upright, laterally correct viewing image. The complete finder also includes other optical components.

Perspective #

The geometric relationship between objects as seen from a viewpoint. Moving the camera changes perspective; changing focal length from the same position mainly changes framing.

Petzval lens #

A historical portrait-lens design combining high speed with characteristic off-axis rendering. Field curvature and swirled backgrounds are associated with some implementations.

Phase-detection autofocus #

Focusing that compares separated views of the lens’s image to estimate focus error. A DSLR’s optical-finder system commonly uses a dedicated module and can require calibration relative to the imaging plane.

Photoflood #

A high-output continuous photographic lamp, traditionally tungsten. It provides bright working illumination but can produce substantial heat and have a short rated life.

Photogenic drawing #

A term associated with Talbot’s early silver-salt images on paper, including contact images. It precedes the developed calotype negative process.

Photogram #

An image made by placing objects in relation to light-sensitive material and exposing it without a camera lens. Transparency, distance and lighting influence the result.

Photogravure #

A photomechanical intaglio printing process in which an inked plate reproduces photographic tones. The finished image is printed in ink rather than formed from light-sensitive silver on the final paper.

Photomultiplier #

A highly sensitive light detector used in equipment including some drum scanners. It amplifies a small light-generated signal rather than recording a complete frame like an area sensor.

Photosite #

A light-sensitive sampling site on a digital sensor. A colour-filtered photosite generally measures one filtered signal; a final full-colour pixel is reconstructed from several samples.

Pictorialism #

A historical photographic movement favouring expressive, often painterly results. Soft focus, manipulated printing and alternative processes were among its approaches.

Pigment print #

A print whose image is made with pigment rather than dye or metallic silver. The term includes several historical processes and many inkjet prints.

Pincushion distortion #

Geometric distortion that bends straight lines inwards towards the image centre near the edges. It is often associated with some telephoto and zoom designs.

Pinhole camera #

A camera forming an image through a small opening rather than a lens. It generally needs long exposures and balances geometric blur against diffraction.

Pixel #

A picture element in a digital image. Sensor-site count, output pixel count and the number of independently resolved subject details are related but not identical.

Pixel peeping #

Inspecting an image at high magnification, commonly one image pixel per screen pixel. It can reveal faults that may not be visible at the intended output size.

Plate camera #

A camera designed for individual photographic plates, usually carried in holders. Some were later adapted for sheet film or roll-film backs.

Plate holder #

A light-tight carrier for a sensitised glass or metal plate. It is not necessarily interchangeable with a sheet-film holder carrying the same nominal size.

Platinum print #

A print in which platinum forms all or part of the image, often alongside palladium. It is valued for its tonal rendering and stable image metal.

Point-and-shoot #

A camera intended for straightforward operation with much of the focusing or exposure automated or fixed. The term includes film and digital cameras.

Polariser #

A filter that selects light according to polarisation, helping control some reflections and darken certain skies. It does not remove all reflections, especially from bare metal.

Positive #

An image whose light-and-dark relationships broadly match the subject. A print, slide or direct-positive plate can all be positive images.

Posterisation #

Visible breaks between tones that should change smoothly. Severe editing, limited bit depth or compression can reveal or create it.

PPI #

Pixels per inch: the pixel density assigned or realised at an image’s output size. Changing the number without resampling changes the stated print size, not the image’s pixel count.

Pre-flash #

A flash emitted before the recorded exposure, commonly for metering or communication. It can trigger simple optical slaves too early.

Pre-focus #

Setting focus before the subject reaches a chosen position. It is useful where autofocus is unavailable or subject movement is predictable.

Preset diaphragm #

A diaphragm arrangement in which a desired aperture is set in advance and a separate action closes the lens to that limit. It predates many automatic diaphragm mechanisms.

Press camera #

A portable camera designed for fast field or news work, often with a rangefinder and large-format film holders. Some offer restricted view-camera movements.

Pressure plate #

A camera component helping hold film at its intended plane. Damage, incorrect settings or debris can affect flatness or scratch the film.

Prime lens #

A lens with one nominal focal length rather than a zoom range. Prime does not automatically mean faster, sharper or better corrected than every zoom.

Printing-out paper #

Paper on which the image becomes visible through exposure to light before final processing. It differs from developing-out paper requiring chemical development of a latent image.

Prism finder #

A finder using a prism to provide an eye-level, correctly oriented view. Medium-format systems may offer it as an alternative to a waist-level hood.

Process lens #

A lens designed for reproduction work, often optimised for flat subjects and particular magnifications. It may have no integral shutter and need substantial camera extension.

Program exposure #

An automatic mode that selects both aperture and shutter speed. Program shift, where offered, changes the combination while maintaining the metered exposure.

Program shift #

Changing the aperture-and-shutter combination chosen in program exposure while retaining approximately the same metered exposure. The shift is limited by lens and camera settings.

Pull processing #

Development adjusted for film exposed at a lower exposure index than its nominal rating, commonly by reducing development. It can control contrast but changes more than a simple speed number.

Push processing #

Development adjusted for film exposed at a higher exposure index, commonly by extending development. It raises density and often contrast but cannot recreate shadow information never adequately exposed.

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Q

Quarter plate #

A historical plate-size designation, commonly about 3¼ × 4¼ inches in British usage. Regional standards and holder designs differ, so measure before buying plates or holders.

Quick release #

A tripod or support fitting that allows equipment to be attached and removed without repeatedly threading the main screw. Similar-looking plates may not be safely interchangeable.

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R

RA-4 #

A standard chromogenic colour-paper processing sequence. It is a paper process, not the C-41 colour-negative film process.

Rangefinder #

A distance-measuring focusing device, often using the alignment of two views. It may be coupled to the lens or used separately with a distance scale.

Rangefinder patch #

The small overlapping-image region used to judge focus in many coupled rangefinders. Faint patches and misalignment can make accurate focusing difficult.

Raw #

A file containing sensor-derived data and metadata before the camera’s normal finished-image rendering. Raw still involves camera-specific encoding and sometimes processing; it is not an untouched photograph in every sense.

Rear standard #

The view-camera assembly carrying the image plane and viewing screen or holder. Its movements can affect focus-plane alignment and image geometry.

Rear-curtain sync #

Flash firing near the end of an exposure. With moving subjects, ambient-light trails commonly appear behind the flash-lit final position.

Rebate #

The unexposed border around a film frame, sometimes including edge printing or perforations. Including it in a scan shows the physical frame boundary but does not prove an image is unedited.

Reciprocity #

The principle that equal combinations of light intensity and exposure duration produce equivalent photographic exposure. Real materials depart from ideal reciprocity under some conditions.

Reciprocity failure #

A change in a photographic material’s response during unusually long or short exposures. Extra exposure and sometimes colour correction may be needed; use the specific film’s data.

Rectilinear lens #

A lens designed to keep straight subject lines straight, apart from residual distortion. Very wide rectilinear views can still stretch objects near the frame edges.

Red window #

A coloured window through which backing-paper frame numbers are read on some roll-film cameras. Its protective value depends on film, lighting and camera design; covers should be used as intended.

Red-eye #

A red pupil reflection caused when flash illumination returns from inside the eye towards the camera. Greater flash-to-lens separation or different lighting can reduce it.

Reflective metering #

Measuring light reflected from the scene towards the camera or meter. Very light, dark or backlit subjects may need interpretation or compensation.

Reflex camera #

A camera using a mirror to provide a viewing image. Single-lens reflex and twin-lens reflex cameras use different viewing arrangements.

Registration distance #

The specified spacing that positions a recording surface relative to a camera or mount reference. Incorrect registration can prevent accurate focusing, even when the lens or holder physically fits.

Release lag #

Delay between operating the shutter release and the start of exposure. Autofocus, metering, mirror motion and camera settings can contribute.

Remjet #

A removable black backing used on certain motion-picture films for anti-halation and other functions. It requires an appropriate removal stage and should not enter an ordinary still-film lab process unannounced.

Replenishment #

Adding specified chemistry to maintain a processing bath’s activity as material passes through it. It follows a defined system rather than simply topping up with water.

Reproduction ratio #

The ratio of image size at the film or sensor to actual subject size. At 1:2, a 20 mm subject forms a 10 mm image.

Resin-coated paper #

RC paper: photographic paper with a plastic-coated paper base. It generally washes and dries more quickly than fibre-based paper.

Resolution #

The ability to distinguish closely spaced detail. Pixel dimensions, optical resolving power and final-output resolution are different measurements.

Reticulation #

A network-like disruption of an emulsion surface, associated with unsuitable processing conditions and abrupt changes. It differs from ordinary film grain.

Retrofocus #

A wide-angle lens design with a back focus longer than its focal length might otherwise suggest. It creates clearance for an SLR mirror.

Reversal film #

Film processed to give a positive transparency rather than a negative. Slide film is the familiar colour example, but black-and-white reversal processes also exist.

Reversing ring #

An adapter mounting a lens with its front towards the camera for close-up work. Aperture control and protection of the exposed rear element need attention.

Rewind #

Returning exposed film to its cassette before opening the camera, particularly with 35 mm systems. Many roll-film cameras wind the exposed film onto a take-up spool instead.

RGB #

Red, green and blue: the additive channels used in many digital colour systems. An RGB file needs a defined colour space for its numerical values to have a consistent colour meaning.

Rim light #

Light outlining the edge of a subject from behind or to the side. It can separate a subject from a similarly toned background.

Rise and fall #

Vertical movement of a view camera‘s lens or image standard. Front rise can include the top of a building while keeping the back vertical and avoiding converging verticals.

Roll film #

Flexible film wound on a spool, with backing paper or another protective arrangement depending on the type. The term often means medium-format roll film rather than 35 mm cassettes.

Roll-film back #

A removable assembly allowing a compatible camera to use roll film. Format, mounting standard and image-plane registration must match the camera.

Rolling shutter #

An exposure or readout in which different image rows or areas are sampled at different times. Movement can appear skewed; electronic and focal-plane mechanical systems can both show time-offset effects.

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S

Safelight #

Darkroom illumination chosen to be sufficiently safe for a particular material under specified conditions. Colour, brightness, distance and exposure duration all matter.

Safety film #

Film using a non-nitrate base, historically including acetate and later polyester. Safety refers to a distinction from nitrate’s fire behaviour, not immunity from deterioration.

Salt print #

A paper print using silver salts within or near paper fibres, associated with early negative-positive photography. It usually has a more matt surface than an albumen print.

Saturation #

The intensity or purity of colour relative to a neutral tone. Increasing it can push colours outside the range a display or print can reproduce.

Scale focusing #

Setting focus by estimating or measuring distance and using the lens distance scale. Depth-of-field markings may provide guidance but depend on the manufacturer’s sharpness assumptions.

Scanning back #

A digital back that builds an image progressively by scanning rather than capturing the entire area at once. Subject and lighting movement can cause artefacts.

Scheimpflug principle #

A geometric relationship used when the lens plane, image plane and plane of sharp focus are tilted relative to one another. Their extended planes meet along a common line; achieving the intended focus also requires correct focus placement.

Screw mount #

A threaded lens attachment. Thread diameter, pitch and registration distance must all match; M39 and M42 labels alone do not settle every compatibility question.

SD card #

Secure Digital removable storage, widely used in later DSLRs. SD, SDHC and SDXC support, capacity limits and speed requirements depend on the camera.

Selenium meter #

An exposure meter using a selenium photovoltaic cell to generate its signal without a battery. Age and storage can affect accuracy, but appearance alone cannot establish its condition.

Self-capping shutter #

A shutter arrangement that shields the film during its resetting or winding cycle. It allows preparation for another exposure without a separate external cap in normal use.

Self-timer #

A delayed shutter release allowing time to enter the frame or let vibration settle. It may be mechanical or electronic.

Sensitometry #

Measurement of how photographic materials respond to exposure and processing. Characteristic curves and density measurements are central tools.

Sepia toning #

Toning that produces a brownish image, traditionally by converting silver into a more stable compound. A digitally applied sepia colour does not provide the same chemical change.

Sheet film #

Individual sheets of photographic film loaded into holders. Each sheet can be exposed and processed separately.

Shift #

Moving a lens or image standard sideways or vertically without changing its angle. It changes framing within the lens’s image circle and differs from tilt.

Short lighting #

Portrait lighting in which the side of the face turned away from the camera receives the main illumination. The effect depends on pose and light placement.

Shoulder #

The part of a characteristic curve where increasing exposure produces progressively smaller density changes. Its behaviour helps describe highlight compression in a negative material.

Shutter #

The mechanism or electronic system controlling when the recording surface receives or integrates light. Leaf, focal-plane and electronic shutters operate differently.

Shutter bounce #

Unwanted rebound of shutter components that can cause uneven or repeated exposure. It is a mechanical fault rather than an exposure-setting choice.

Shutter capping #

A focal-plane shutter fault in which curtain timing prevents part or all of the frame from receiving the intended exposure. It often becomes more obvious at faster speeds.

Shutter cocking #

Preparing the shutter mechanism for its next exposure by tensioning or setting it. On some cameras it is linked to film advance; on others it is separate.

Shutter priority #

An automatic exposure mode in which the photographer selects shutter speed and the camera chooses aperture. Common markings include S and Tv.

Shutter speed #

The nominal duration of exposure at a point on the recording surface. A fast focal-plane setting does not mean the whole frame is uncovered simultaneously for that interval.

Silver halide #

A family of light-sensitive silver compounds used in photographic emulsions, including silver bromide, chloride and iodide. Their proportions and structure affect material behaviour.

Silver mirroring #

A reflective sheen arising from deterioration and redistribution of silver in a photographic image. It often appears in dense areas of older prints or negatives.

Single-lens reflex #

SLR: a camera using the taking lens and a reflex mirror for viewing. The format can be film or digital; SLR alone does not mean DSLR.

Slide #

A positive transparency, often mounted for projection or viewing. The word commonly refers to reversal-film frames rather than negative film.

Slide duplicator #

An attachment or copying arrangement for photographing transparencies. Illumination uniformity, alignment and lens magnification determine the quality of the copy.

Slow sync #

Flash combined with a relatively long shutter exposure to record more ambient light. It can produce both sharp flash-lit detail and movement trails.

SmartMedia #

A thin removable memory-card format used in some early digital cameras. Capacity and voltage compatibility require attention, and it is not interchangeable with SD.

Snoot #

A tube or cone fitted to a light to restrict its beam. It concentrates the area illuminated rather than increasing the lamp’s total output.

Soft focus #

Deliberately softened rendering, often with a sharp core surrounded by a glow. It differs from simply focusing the lens at the wrong distance.

Softbox #

A light modifier using a diffusing front panel, usually with reflective sides. Its size and distance from the subject determine much of the resulting softness.

Solarisation #

Historically, tonal reversal from extreme exposure; often used loosely for the Sabattier effect, a partial reversal produced by re-exposure during development. The mechanisms and terms should be distinguished.

Speedlight #

A common term for a portable electronic flash, especially a shoe-mounted unit. Manufacturer spellings such as Speedlight and Speedlite are brand-specific.

Spherical aberration #

An aberration in which rays passing through different zones of a lens focus at different distances. It can affect sharpness, bokeh and aperture-related focus shift.

Split toning #

Giving different colour treatments to different tonal regions of an image. It can be achieved through selected chemical toning methods or digital processing.

Split-grade printing #

Making separate enlarger exposures through low- and high-contrast filters on variable-contrast paper. The exposures combine to control highlight and shadow relationships.

Split-image rangefinder #

A focusing-screen aid splitting part of the image into displaced sections that align at focus. It is an SLR screen aid, distinct from a separate coupled rangefinder camera.

Sports finder #

An open-frame or direct-view finder designed for rapid framing, often with both eyes open. It usually provides less precise close-range framing than the taking lens‘s ground-glass image.

Spot metering #

Measuring brightness over a small area of the frame. The photographer decides how that measured tone should be rendered rather than assuming every spot should become middle grey.

Spotting #

Retouching small print or image defects, often caused by dust. Traditional print spotting uses dyes or pigments; digital spotting uses editing tools.

Sprocket holes #

Perforations along film edges that engage transport mechanisms. Damaged perforations can prevent accurate advance or cause a jam.

sRGB #

A widely supported RGB colour space used for web images and many consumer workflows. A file should be converted appropriately rather than merely relabelled with a different profile.

Stand development #

Development with very limited agitation after an initial period. Results depend on film, developer, dilution and handling; uneven development is a possible drawback.

Step-up ring #

An adapter allowing a larger-diameter filter to fit a smaller lens filter thread. A step-down ring does the reverse and may cause vignetting.

Stereoscopy #

Creating an impression of depth by presenting different views to the two eyes. Stereo cameras typically record a separated pair for a suitable viewer.

Stop #

A relative exposure step representing a factor of two. Opening one stop doubles light transmission in the ideal f-number sequence; closing one stop halves it.

Stop bath #

A processing bath that arrests or sharply slows development, commonly by neutralising an alkaline developer. The correct bath depends on the process.

Stop-down metering #

Metering with the diaphragm closed to the taking aperture. It is useful where the camera cannot account for an aperture setting while the lens remains open.

Strap lug #

An attachment point for a camera strap. Wear, loose fittings and incompatible clips can compromise how securely it holds equipment.

Stroboscopic flash #

Repeated flashes during one exposure, recording several positions of a moving subject. Flash power and repetition rate are limited by the equipment.

Subminiature #

A camera or format substantially smaller than conventional 35 mm still photography. Examples include Minox formats, but the category has no single universal boundary.

Subtractive colour #

Colour formation by materials that absorb parts of incident light, typically cyan, magenta and yellow dyes or inks. Most colour photographic prints use subtractive image formation.

Subtractive filter #

A colour filter that absorbs selected wavelengths from the light reaching film or paper. Cyan, magenta and yellow filtration is common in colour printing.

Sunny 16 #

A daylight exposure guideline: in bright sun, start around f/16 with a shutter time near the reciprocal of the ISO number. Atmosphere, subject and desired rendering can require adjustment.

Swing #

Rotation of a view-camera standard about a vertical axis. It changes the relationship between lens plane, image plane and plane of sharp focus.

Sync speed #

The fastest shutter setting normally allowing a conventional short electronic flash to illuminate the whole frame. High-speed sync and special shutter designs are exceptions requiring compatible operation.

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T

T setting #

A time-exposure setting that commonly opens the shutter with one operation and closes it with another. The exact release sequence depends on the shutter.

T-stop #

A lens-aperture value calibrated for actual light transmission rather than geometry alone. It is particularly common in cinema-lens markings.

Take-up spool #

The spool receiving film as it advances through the camera. In many roll-film cameras the empty supply spool becomes the next roll’s take-up spool.

Taking lens #

The lens that forms the recorded photograph. In a twin-lens reflex camera it is separate from the viewing lens.

Talbotype #

Another name associated with the calotype process and its paper negatives. Historical usage can extend to prints made from those negatives.

Tank development #

Processing film in a light-tight tank after loading in appropriate darkness. A tank designed for daylight operation can be opened only at the stages its design permits.

Telecentricity #

A property describing chief-ray geometry in a lens system. Image-side telecentric designs send chief rays towards the sensor more nearly perpendicular to its surface.

Teleconverter #

An optical attachment between lens and body that increases effective focal length. It reduces the effective maximum aperture and may affect image quality and autofocus compatibility.

Telephoto #

Strictly, a long-focus lens design with physical length shorter than its focal length. In everyday use it also means a lens with a narrow angle of view.

Test strip #

A small printing sample exposed in steps to judge exposure, contrast or colour balance. It reduces waste before making a full print.

Thin negative #

A negative with relatively low image density. Underexposure, underdevelopment or other causes may be responsible; appearance alone does not identify the cause.

Thread mount #

Another name for a Screw mount. Thread size and flange distance must both be correct for useful compatibility.

Three-colour separation #

Recording or producing separate images representing colour components, later combined for colour reproduction. Historical methods used filters and multiple plates or films.

Through-the-lens metering #

TTL metering: measuring light through the taking lens. It can account for filters and extension, but the implementation and operating limits vary.

TIFF #

Tagged Image File Format: a flexible image format often used for high-quality scans and edited files. TIFF can use different bit depths, colour models and compression methods.

Tilt #

Rotation of a lens or camera standard about a horizontal axis. It changes the orientation of the plane of sharp focus rather than merely adding more depth of field everywhere.

Tilt-shift lens #

A lens allowing tilt and shift movements on a camera with a fixed body. Its image circle, mechanical clearances and metering instructions limit practical use.

Tintype #

A direct-positive-looking collodion image on dark-coated iron. Also called a ferrotype, it is not normally made on tin.

Toe #

The lower-exposure region of a photographic characteristic curve, where response departs from its straighter middle section. It influences how weakly exposed tones separate.

Tonal range #

The span and distribution of tones in an image or material. A scene’s range, a negative‘s densities and a print’s reflectances are different parts of the photographic chain.

Tone curve #

A mapping from input brightness values to output values, used in digital processing and described differently in film sensitometry. Its shape controls contrast across tonal regions.

Toning #

Chemical alteration of a photographic image to change its colour, stability or both. Digital toning changes appearance without providing the same material transformation.

Transparency #

A positive image viewed by transmitted light, such as a slide or glass colour plate. It is not a synonym for every piece of transparent photographic film.

Triplet #

A three-element lens design, classically exemplified by the Cooke triplet arrangement. Variations balance correction, speed and manufacturing simplicity.

Tripod collar #

A rotating support ring on a lens that transfers the load to a tripod near the equipment’s balance point. It can allow portrait orientation without tipping the head sideways.

TTL flash #

Flash exposure measured through the taking lens. Film-era systems may measure light during the exposure; many DSLR systems use a metering pre-flash instead.

Tungsten-balanced film #

Colour film designed for a specified tungsten-like light source, commonly around 3200 K. Used in daylight without correction, it usually produces a blue cast.

Twin-lens reflex #

TLR: a camera with separate taking and viewing lenses, usually linked for focus. The viewing image commonly appears laterally reversed in a waist-level finder.

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U

Ultrasonic motor #

A lens-focusing motor using ultrasonic vibration. Terms such as USM and Silent Wave Motor belong to particular manufacturers, and implementations differ.

Underexposure #

Less exposure than intended or needed for the desired result. Increasing development or digital brightness cannot fully restore information that was never recorded above the noise or film threshold.

Unsharp masking #

A sharpening technique using a blurred version of an image to increase edge contrast. It can improve apparent crispness but does not recover unlimited missing detail.

UV filter #

A filter intended to reduce ultraviolet transmission, historically useful with some films and conditions. On many digital cameras it mainly serves as optional front-element protection and can introduce reflections.

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V

Variable ND #

A neutral-density filter whose strength is adjusted by rotating polarising elements. Strong settings can produce uneven darkening, colour shifts or an X-shaped pattern.

Variable-contrast paper #

Black-and-white printing paper whose contrast changes with the colour of the exposing light. Matched filters or a suitable enlarger head select the working contrast.

Vernacular photography #

Everyday photographs made for personal, practical or anonymous uses rather than primarily as exhibited fine art. Family snapshots and routine record photographs are examples.

View camera #

A camera with separate lens and image standards, commonly joined by bellows and offering movements. Composition and focus are usually checked on a ground glass.

Viewfinder coverage #

The proportion of the recorded frame visible in a finder. A finder below 100% coverage includes less than the camera records, leaving extra image around the viewed edges.

Viewfinder magnification #

The apparent size of the finder image under specified test conditions. Numbers cannot be compared reliably without considering lens focal length, focus distance and format.

Vignetting #

Darkening towards the image corners, caused by optical geometry, obstruction or sensor-related effects. A hood or stacked filters can create mechanical vignetting.

Vinegar syndrome #

Deterioration of cellulose acetate materials associated with acetic acid release. It can cause odour, shrinkage and deformation and is a preservation issue rather than a processing effect.

Vintage #

An imprecise age-related description rather than a technical camera class. In print collecting, a vintage print often means one made near the time of the negative, with conventions varying by collection.

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W

Waist-level finder #

A finder viewed from above, usually through a folding hood. On many reflex cameras its image is upright but laterally reversed.

Water bath development #

A development method alternating or combining developer action with water stages to influence image development. The intended effect depends on the material and procedure.

Waterhouse stop #

A plate with a fixed-size aperture inserted into a slot in a lens. A set of plates provides different openings without an iris diaphragm.

Wet plate #

A photographic plate prepared and exposed while its coating remains wet, most famously wet collodion. Preparation, exposure and development must be coordinated near the camera.

Wetting agent #

A final-rinse additive that reduces surface tension and helps water drain from film. Excess concentration or contamination can leave deposits rather than prevent them.

White balance #

A digital adjustment that maps a chosen reference to neutral and influences the rendering of other colours. It cannot fully correct every mixed-light or incomplete-spectrum problem.

White point #

The reference used for output white or a chosen neutral white chromaticity. It can describe tonal mapping or colour management, depending on context.

Whole plate #

A historical plate-size designation, commonly about 6½ × 8½ inches in British usage. Nominal names and actual holder dimensions vary across traditions.

Wide open #

Using a lens at its maximum aperture. Bright viewing, shallow depth of field, vignetting and aberration behaviour may differ from those at smaller apertures.

Wide-angle lens #

A lens giving a wider angle of view than a normal lens for the format. Focal length must be interpreted with the frame size.

Winder #

A powered film-advance accessory, often simpler or slower than a motor drive. The label does not establish the exact shooting rate or rewind capability.

Woodburytype #

A photomechanical printing process using a moulded relief and pigmented gelatin to reproduce continuous tones. The final print is not a conventional silver photographic print.

Working distance #

The clearance between the front of the lens or equipment and the subject at a stated focus. It differs from focus distance measured from the film or sensor plane.

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X

X contact #

A shutter synchronisation contact timed for electronic flash. M and other historical bulb settings use different timing and should not be treated as interchangeable.

X-sync #

The synchronisation setting or speed for conventional electronic flash. It depends on when the shutter permits the full frame to receive the flash.

xD-Picture Card #

A removable memory-card format used in some early digital cameras. Its physical connector and compatibility differ from SD and CompactFlash.

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Y

Yellow filter #

A filter commonly used with black-and-white film to alter tonal relationships, often darkening blue skies relative to clouds. The result depends on the film’s spectral sensitivity and the light.

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Z

Zone focusing #

Choosing a focus setting and aperture so a useful range of subject distances is acceptably sharp. It is common in street photography with scale-focus cameras.

Zone System #

An exposure and development framework associated with Ansel Adams and Fred Archer, relating scene values to intended image tones. It is a method of control, not merely a numbered grey scale.

Zoom lens #

A lens with a continuously variable focal-length range. Maintaining focus while zooming depends on the design; many still-camera zooms are not strictly parfocal.

Zoom ratio #

The longest focal length of a zoom divided by its shortest. A 3× zoom describes a range ratio, not a fixed magnification or a comparison with human eyesight.

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