A Glossary of Photographic Terms A - G

Acetone
A solvent chemical used in certain processing solutions that contain materials not normally soluble in water.

Achromatic
Is a lens system that has been corrected for chromatic aberration.

Acid Hardener
Is a substance used in acid fixer to help harden the gelatine of the emulsion.

Acutance
A measure of the sharpness with which the film can produce the edge of an object.

Adapter Ring
Is a circular mount, available in several sizes enabling accessories such as filters to be used with lenses of different diameters.

Additive Palette
This is a set of colours selected to represent, as closely as possible, the colours in the original source image.

Additive Primary Colours
Red, Green, Blue; The 3 colours used to create all other colours when direct, or transmitted light is used .They are called additive primaries, because when those are superimposed they produce white.

Adjustable Camera
A camera with manually adjustable settings for distance, lens openings, and shutter speeds.

Adjustable-Focus Lens
A lens that has adjustable distance settings, as apposed to fixed focus. These lenses can be manual or auto focus

Advanced Photo System (APS)
A new standard in consumer photography developed by Kodak and four other System Developing Companies - Canon, Fuji, Minolta and Nikon - based on a new film format and photo-finishing technologies.

Advantix
Kodak brand name that identifies the Advanced Photo System.

Agitation
Keeping photographic chemicals (developer, stop bath, or fixer) in a gentle, uniform motion whilst processing film or paper. Agitation helps to speed and achieve even development and prevent spotting or staining.

Air Bubbles
Clear areas, usually circular, on film, produced by bubbles of air trapped on the film during development. They are caused by insufficient agitation while developing the film.

Alkalinity
Denotes the degree of alkali in a solution, measured in pH values. All values above pH 7 are alkaline.

Ambient Light
The name sometimes given to available light that completely surrounds a subject, sometimes called 'wrap around'. Light already existing in an indoor or outdoor setting that is not caused by any illumination supplied by the photographer.

Amidol
Soluble reducing agent which works at low pH values

Anastigmatic
Is a compound lens which has been corrected for the lens aberration " astigmatism ".

Angle of incidence
When light strikes a surface it forms an angle with an imaginary line known as the : normal, which is perpendicular to the surface. The angle created between the incident ray and the normal is referred to as the angle of incidence.

Angle of flash coverage
The measurement in degrees of the angle formed by lines projecting from the centre of the flash to the extremities of the field of coverage.

Angle of View
The area of an image that a lens covers. Angle of view is determined by the focal length of the lens. A wide-angle lens (short-focal-length) includes more of the scene-a wider angle of view-than a normal (normal-focal-length) or telephoto (long-focal-length) lens.

ANSI
Is a rating for photographic materials devised by the American National Standards Institute.

Anti-fogging agent
Constituent of a developer that inhibits or reduces fogging during development.

Anti-halation backing
A dye used on backs of most films capable of absorbing light which passes through the emulsion. This way it reduces the amount extraneous light can be reflected from the camera back through the emulsion.

Anti-reflection coating
One or more thin layers of refractive material ( often magnesium fluoride ) coated upon the surface of a lens to minimize surface reflection. It is deposited on the lens by vaporization of the metal in vacuum.

Aperture
The opening in a camera lens through which light passes to expose the film. The size of aperture is either fixed or adjustable. Aperture size is usually calibrated in f-numbers-the larger the number, the smaller the lens opening.

Aperture priority
An exposure mode on an automatic or auto-focus camera that lets you set the aperture while the camera sets the shutter speed for proper exposure. If you change the aperture, or the light level changes, the shutter speed changes automatically. Apart from the sport or action arena, aperture priority is the most common & effective automatic preference in photography. It can also explained as automatic exposure system in which the lens aperture is set by the photographer, and the camera sets the shutter speed. Can be used in the stop-down mode with any lens that does not interfere with the metering system.

Aperture ring
A ring, located on the outside of the lens usually behind the focusing ring, which is linked mechanically to the diaphragm to control the size of the aperture; it is engraved with a set of numbers called f-numbers or f-stops.

Aplanat
Is a lens which has been corrected for spherical aberration.

Apochromatic
The inability to bring light of all colours to the same plane of focus is known as chromatic aberration. Light refraction is a function of wavelength, and as such each colour is normally brought to as lightly different plane of focus. By using complex lens designs, special glass materials and coating, designer can bring the colours within a much narrower focus. When such a lens is designed it is said to be Apochromatic.

Archival Image
An image meant to have lasting utility. Processed to exacting standards and often toned with selenium or gold. Archival images are also often stored digitally at a high resolution and quality. The file format most often associated with archival images is TIFF, or Tagged Image File Format, as compared to on-screen viewing file format, which are usually JPEG's and GIF's.

Archival Processing
Processing designed to protect a print or negative as much as possible from premature deterioration caused by chemical reactions.

Artificial light
Generally the term refers to light specially set up by the photographer, such as flash or photo lamps. Photographic emulsion have different sensitivity to daylight and artificial light, and film may be rated for either type.

A.S.A.
An absolute term indicating a film's sensitivity to light. The letters stands for American Standards Association . The term as been replaced by ISO standing for International Standards Organization.

Aspect Ratio
The ratio of width to height in photographic prints - 2:3 in 35 mm pictures to produce photographs most commonly measuring 3.5 x 5 inches or 4 x 6 inches; Advanced Photo System cameras deliver three aspect ratios as selected by the user.

Aspherical lens
A lens whose curved surface does not conform to the shape of a sphere; lenses are usually ground or molded with spherical surfaces; because a spherical surface lens has difficulty in correcting distortion in ultra-wide-angle lenses or coma in large-aperture lenses brought about by spherical aberration, an Aspherical lens is used.

Astigmatism
A lens aberration or defect that is caused by the inability of a single lens to focus oblique rays uniformly. Astigmatism causes an object point to appear as a linear or oval-shaped image.

Autochrome
Early commercial colour photography process in which the principals of additive colour synthesis were applied.

Automatic exposure setting
Automatically adjusts the exposure to match particular light settings.

Automatic flash
An electronic flash unit with a light-sensitive cell that determines the length of the flash for proper exposure by measuring the light reflected back from the subject.

Auto focus (AF)
System by which the camera lens automatically focuses the image of a selected part of the picture subject.

Automatic Camera
A camera with a built-in exposure meter that automatically adjusts the lens opening, shutter speed, or both for proper exposure.

Auto-winder
Film wind-on mechanism which moves the film on one frame each time the shutter is released.

Available light
The light that is present in a scene, either indoors or out, that is not added by the photographer. Also called ambient light or existing light.

Axis lighting
Light pointed at the subject from a position close to the camera's lens.

B (Bulb) Setting
A shutter-speed setting on an adjustable camera that allows for time exposures. When set on B, the shutter will stay open as long as the shutter release button remains depressed.

Background
The part of the scene that appears behind the principal subject of the picture.

Backlighting
Light coming from behind the subject, toward the camera lens, so that the subject stands out vividly against the background. Sometimes produces a silhouette effect.

Back-Printing
Information printed on the back of a picture by the photo-finisher. The system standard requires the printing of frame number, film cassette number and processing date automatically on the back of each Advanced Photo System print; may also include more detailed information, such as customized titles and time and date of picture-taking.

Backing
The dark coating, normally on the back of a film, but sometimes between emulsion and the base, to reduce halation. The backing dye disappears during the processing.

Back focus
Distance between the back surface of the lens and the image plane, when the lens is focused at infinity.

Baffle
A type of shield that prohibits light from entering an optical system.

Backlight control
An exposure compensation introduced when the subject of a picture is lit from behind ( which can fool a camera's metering system, creating a silhouette effect ).

Back-lighting
Light coming from behind the subject.

Balance
Placement of colours, light and dark masses, or large and small objects in a picture to create harmony and equilibrium.

Balanced fill-flash
In balanced fill-flash operation, flash output is controlled to keep it in balance with the ambient light on the scene. Nikon offers Automatic balanced Fill-Flash where flash output is automatically compensated to be in balance with the ambient light.

Barn door
Are an accessory used on spotlights and flood lamps to control the direction of light and width of the beam.

Barrel
The chassis of a lens. It usually is cylindrical and contains the lens element and iris diaphragm.

Barrel distortion
A lens aberration or defect that causes straight lines to bow outward away from the centre of the image.

Base
The material on which the emulsion is coated on film, photographic paper or videotape. Available in a choice of materials, including paper, cellulose, triacetate, glass.

Base+ fog
The optical density of an unexposed area of processed film. This takes into consideration the density of both the base and the emulsion.

Base Exposure Time
The initial exposure time used for making a "straight" print. This is determined by using a test strip.

Batch numbers
Set of numbers printed on packages of sensitive materials to indicate common production coating.

Bayonet lens mount
A method of mounting a lens onto a camera body. The lens is inserted into the camera and given a short turn to lock it into place. Except for a few instances, a bayonet mount camera will not accept bayonet mount lenses made by a different manufacturer. The most common method of lens mounting.

Bellows
The folding (accordion) portion in some cameras that connects the lens to the camera body. Also a camera accessory that, when inserted between lens and camera body, extends the lens-to-film distance for close focusing.

Bellows factor
The exposure compensation necessary when focusing on close subjects, which becomes necessary when the subject is closer than ten times the focal length of the lens. As a lens is placed closer to the subject, focusing the lens causes it to move farther from the film, and, therefore, less light falls on the film. Consequently the exposure must be increased.

Between-The-Lens Shutter
A shutter whose blades operate between two elements of the lens.

Bi-concave lens
A simple lens or lens shape within a compound lens, whose surfaces curve toward the optical centre. Such a lens causes light rays to diverge.

Bleaching
Lightening selected areas of the image using bleaches or reducers. The most common bleach is potassium ferricyanide. Other tonal techniques include burning, dodging, flashing, and toning.

Blow-up
An enlargement; a print that is made larger than the negative or slide.

Blur
The art of softening the detail of a image. The process can be applied selectively to portions of an image.

Bottom weighted
Refers to the area of the picture that the camera will meter for exposure. When making an auto exposure the camera is programmed to look at a number of spots in the scene, and if the camera was designed to use bottom weighted metering, most of those spots will be in the lower half of the picture. (See centre weighted and exposure.)

Boom
A adjustable metal arm, attached to a firm stand, on which lighting can be mounted. Some booms are also made to support camera.

Bounce flash
Flash illuminating a subject by reflection off a surface as opposed to direct flash, which is flash light aimed straight at the subject.

Bounce Lighting
Flash or tungsten light bounced off a reflector (such as the ceiling or walls) to give the effect of natural or available light.

Box camera
Simple camera with a fixed, single-element lens and a light-tight box to hold the film. The shutter and aperture are usually pre-determined and unalterable (typically 1/25 sec at ƒ11.) Early consumer cameras developed by George Eastman were box cameras (e.g. the “Brownie” camera) . They could not be focused, per se. The lens was set to a hyper-focal distance that gave acceptably-sharp pictures if the subject was a given distance from the camera and correct exposure depended upon bright sun illuminating the scene.

Bracketing
Taking additional pictures of the subject through a range of exposures-both lighter and darker-when unsure of the correct exposure.

Bracket flash
Often called handle mount flash. It comprised of one arm of the L-shaped bracket extends under the camera body and uses the camera's tripod socket to mount the camera on the bracket. The vertical arm of the bracket serves as a handle and mounts a flash unit in an accessory shoe often on top of the handle portion, but there are other methods. Flash mounted in a bracket usually requires a separate electrical cord to make the electrical connection between camera body and flash unit.

Brightness
The balance of light and dark shades in a image. Brightness is distinct from contrast, which measures the range between the darkness and lightest shades in a image. Brightness determines the intensity of shades; contrast determines the number of shades you get.

Brightness range
The difference in luminance between the darkest and lightest areas of the subject, in both negative and print.

Brilliance
The intensity of light reflected from a surface. It is sometimes an alternative term for luminosity.

Built-in light meter
A reflective exposure meter that is a built-in component of a camera so that exposures can be easily made for the cameras position.

Bulb
A shutter setting marked B at which the shutter remains open as long as the shutter release is held down. This is used for time exposures that are longer than your camera's preset shutter speeds.

Bulk film
Film produced in very long, uncut strips - rolls that are too long to fit into cameras not equipped with a bulk camera back accessory. Many photographers buy their film in bulk, then load the bulk film into a “bulk film loader” which permits them to cut the bulk film into however many frames they wish, and to load the smaller strips into film cartridges that permit film reloading. It is an economical way to purchase film.

Burning-In
Giving additional exposure to part of the image projected on an enlarger easel to make that area of the print darker. This is accomplished after the basic exposure by extending the exposure time to allow additional image-forming light to strike the areas in the print you want to darken while holding back the image-forming light from the rest of the image. Sometimes called printing-in.

C-41
Processing system for colour negative film.

Cable release
Its a flexible cable used for firing a camera shutter. Particularly useful for slow shutter speed and time exposures, when touching the camera may cause camera vibration and blurring of the image.

Camera Angles
Various positions of the camera (high, medium, or low; and left, right, or straight on) with respect to the subject, each giving a different viewpoint or effect.

Camera movements
Are mechanical system most common on large format camera which provide the facility for lens and film plane movement from a normal standard position.

Candle meter
Also known as lux and defined as the illumination measured on a surface at a distance of one meter from a light source of one international candle power.

Candid Pictures
Un-posed pictures of people, often taken without the subject's knowledge. These usually appear more natural and relaxed than posed pictures.

Cartridge
A light tight, factory-loaded film container that can be placed in and removed from the camera in daylight.

Catch-light
The reflection of a light in the subject's eyes in a portrait.

Cast
An image's overall shift in colour at any point in the process, from photography to scanning and image processing. The almost white and almost black areas of an image tend to take on a colour -- often red, blue, or yellow -- and display an unnatural appearance.

CC filters
Yellow, Magenta, Cyan, Red, Green and blue filters that can change the colour balance of the resulting pictures. These filters are most useful for duplicating slides. They come in a range of densities from 0.025 to 0.50 . They are designated by the letters CC the density (without the decimal), and a letter indicating the hue, for example CC10M.

Centre weighted
Refers to the area of the picture that the camera will meter for exposure. When making an auto exposure the camera is programmed to look at a number of spots in the scene, and if the camera was designed to use centre weighted metering, most of those spots will be in the centre area of the picture.

Changing Bag
A light proof black fabric bag that permits film and other light-sensitive materials to be handled in normal room light. Has a double zipper on one end and two armholes with elastic sleeves on the other.

Characteristic Curve Regions
The characteristics curves are shaped similar to a ski ramp, with the bottom portion sloping up slightly (called the "toe"), a steep middle portion known as the "straight line" and a top portion that begins to flatten out (called the "shoulder"). Both film and paper characteristic curves are similar in shape.

Chromatic aberration
An optical defect of a lens which causes different colours or wave lengths of light to be focused at different distances from the lens. It is seen as colour fringes or halos along edges and around every point in the image.

Chromaticity
The colour quality of light which is defined by the wavelength ( hue ) and saturation. Chromaticity defines all the qualities of colour except its brightness.

Chrominance
A colour term defining the hue and saturation of a colour. Does not refer to brightness.

Cibachrome
A colour printing process that produces colour prints directly from colour slides.

CIE
Commission Internationale de L'Éclairage. An international group that developed a universal set of colour definition standards in 1932.

CIE LAB ( L*a*b* )
A colour model to approximate human vision. The model consists of three variables: L* for luminosity, a* for one colour axis, and b* for the other colour axis.

Clearing Agent
A chemical that neutralizes hypo in film or paper, reducing wash time and helping to provide a more stable image.

Clearing time
Is the length of time needed for a negative to clear in a fixing solution.

Close-Up
A picture taken with the subject close to the camera-usually less than two or three feet away, but it can be as close as a few inches.

Close-Up Lens
A lens attachment placed in front of a camera lens to permit taking pictures at a closer distance than the camera lens alone will allow.

C-mount
A threaded means of mounting a lens to a camera.

Coated Lens
A lens covered with a very thin layer of transparent material that reduces the amount of light reflected by the surface of the lens. A coated lens is faster (transmits more light) than an uncoated lens.

Code notch
Individually distinctive notches located near one corner on photographic sheet of film for product identification purposes. When viewed correctly, these code notches will appear at top-left corner or bottom-right corner of the sheet. In this position the emulsion layer is always facing away from the observer.

Cold colours
Are colours at the blue end of the spectrum that suggest a cool atmosphere.

Cold Light Enlarger
A diffusion type of enlarger with fluorescent lamps as the light source. These types of enlarger heads scatter the light more evenly across the surface of the negative. One advantage of the cold light head is that it can render more subtle tonal gradations and will minimize the effect of dust and scratches on the negative which are translated to the print. The cold light head does generate some heat while in operation, but considerably less than its condenser enlarger counterpart.

Colour Balance
How a colour film reproduces the colours of a scene. Colour films are made to be exposed by light of a certain colour quality such as daylight or tungsten. Colour balance also refers to the reproduction of colours in colour prints, which can be altered during the printing process.

Colour cast
The effect of one colour dominating the overall look of an image. Often caused by improper exposure, wrong film type, or unusual lighting conditions when shooting the original image.

Colour compensating filters
Gelatin filters that can be used to adjust the colour balance during picture taking or in colour printing. Abbreviated CC filters.

Colour conversion filters
Deeply coloured filters that enables colour film to be used with light of a different colour temperature than it was intended. The 80-series filters are blue enabling you to use daylight-balance film with tungsten light; the 85-series are amber and let you see tungsten film with daylight or electronic flash.

Colour correction
The process of adjusting an image to compensate for scanner deficiencies or for the characteristics of the output device.

Colour-correction filter
Filters used with black-and-white film to correct for the difference in films sensitivity to colour as compared with that of the human eye. Without a filter, for example clouds would be all but invisible against a light blue sky; a yellow filter would darken the sky, thus creating contrast between the sky and the clouds.

Colour coupler
A colourless substance contained in colour film emulsions that, when exposed to chemical developing baths forms the colour dyes that make up part of the layers of processed colour films.

Colour curves
A mechanism for controlling colour changes, and matching colours. Colour curves are set by user-adjustable lookup tables that define a colour transform, which may be applied to each primary additive colour in the image.

Colour depth
The amount of colour information recorded by each CCD pixels. The greater the depth, expressed in bits, the truer and richer the colour is recorded.

Colour gamut
The range of colours that can be formed by all possible combination of colorants in any colour input system.

Colour head
A device on a enlarger that contains adjustable built-in filters (yellow, cyan and magenta) for colour printing.

Colour negative
Film processed as a negative image from which positive prints can be made.

Colour reversal
Film designed to produce a normal colour positive on the film exposed in the camera for subsequent viewing by transmitted light.

Colour saturation
The purity of a colour resulting from the absence of black and white.

Colour temperature
The temperature (measured in degrees Kelvin) to which an object would have to be heated before it would radiate a given colour. Each type of light can also be represented by a numerical colour temperature, here are the (rough) colour temperatures of typical lighting conditions:

Type of light Colour temperature
Incandescent 2500K - 3500K
Twilight 4000K
Fluorescent 4000K - 4800K
Sunlight 4800K - 5400K
Cloudy daylight 5400K - 6200K
Shade 6200K - 7800K

Colour temperature meter
A device for estimating the colour temperature of a light source. Usually used to determine the filtration needed to match the colour balance of the light source with that of standard types of colour film.

Colour printing filters
Yellow, Magenta and Cyan filters used when making colour prints, in order render the colours correctly or as desired. They come in a range of density from 0.025 to 0.50.

Coma
A lens aberration or defect that causes rays that passes obliquely through the lens to be focused at different points on the film plane.

Compensating developer
A developer designed to compress the general contrast range in a negative without influencing gradation in the shadow and highlight areas.

Complementary colours
1. Any two colours of light that when combined include all the wavelengths of light and thus produce white light.
2. Any two dye colours that when combined absorbs all wavelengths of light and thus produce black. A colour filter absorbs light of its complementary colour and passes light of its own colour.

Compound shutter
Is a shutter consisting of a number of metal leaves arranged symmetrically around the edge of the lens barrel

Composition
The pleasing, aesthetic, arrangement of the elements within a scene-the main subject, the foreground and background, and supporting subjects.

Compur shutter
A well known German brand of compound shutter.

Condenser
An optical system which concentrates light rays from a wide source into a narrow beam. Condensers are used in spotlights and enlargers.

Condenser Enlarger
An enlarger with a sharp, un-diffused light that produces high contrast and high definition in a print. Scratches and blemishes in the negative are emphasized.

Contact Print
A print made by exposing photographic paper while it is held tightly against the negative. Images in the print will be the same size as those in the negative.

Contrast
The range of difference in the light to dark areas of a negative, print, or slide (also called density); the brightness range of a subject or the scene lighting.

Contact print
An image made by placing a negative in tight contact with a sheet of photographic paper or other piece of film, then exposing it to light. Although it is usually done with a photographic negative to make a positive. Contact prints can also be made positive to negative, or, with special types of film, positive or negative to negative.

Contact Printer
A device used for contact-printing that consists of a light tight box with an internal light source and a printing frame to position the negative against the photographic paper in front of the light.

Contamination
Traces of chemicals that are present where they don't belong, causing loss of chemical activity, staining, or other problems.

Continuous tone
An image, such as a original photographic transparency or print, in which the tones or colours blend smoothly from one to another; also known as a contone.

Contrast
The difference in brightness between the lightest and darkest parts of a photographic subjects, negative, prints or slide. Contrast is affected by the subject brightness, lighting, film type degree of development, the grade and surface of the printing paper, and the type of enlarger head used.

Contrast filter
A coloured filter used on a camera to lighten or darken selected colours in a black and white photograph. For example , a green filter used to darken red flowers against green leaves.

Contrast Grade
Numbers (usually 1-5) and names (soft, medium, hard, extra-hard, and ultra hard) of the contrast grades of photographic papers, to enable you to get good prints from negatives of different contrasts. Use a low-numbered or soft contrast paper with a high contrast negative to get a print that most closely resembles the original scene. Use a high-numbered or an extra-hard paper with a low-contrast negative to get a normal contrast paper.

Contrasty.
Higher-than-normal contrast including very bright and dark areas. The range of density in a negative or print is higher than it was in the original scene.

Convex lens
A simple lens which causes rays of light from a subject to converge and form an image.

Correction filter
A coloured filter used on a camera lens to make black and white film produce the same relative brightness perceived by the human eye. For example, a yellow filter used to darken a blue sky so it does not appear excessively light.

Cool
Refers to bluish colours that by association with common objects (water, ice, and so on) give an impression of coolness.

CP filters
Abbreviation for colour printing filters.

Convergence
The phenomenon in which lines that are parallel in a subject, such as the vertical lines of a building, appear nonparallel in a image.

Crossed curves
A destructive phenomenon in image processing that causes different colours to increase in density at different rates or gammas. The visual effect is a colour difference from image highlight to image shadow.

Crop (cropping)
To trim the edges of an image, often to improve the composition. Cropping can be done by moving the camera position while viewing a scene, by adjusting the enlarger or easel during printing or by trimming the finished print.

Cropping
Printing only part of the image that is in the negative or slide, usually for a more pleasing composition. May also refer to the framing of the scene in the viewfinder.

Crossed polarization
A system of using two polarizing filters, one over the light source and one between the subject and the lens. Used in investigations of stress areas in engineering and architectural models.

Dark-cloth
Material used to cover the photographer's head and camera to block surrounding light in order to better view the image on the camera's ground glass viewing screen.

Darkroom
A light tight area used for processing films and for printing and processing papers; also for loading and unloading film holders and some cameras.

Daylight film
Film balance to give correct rendition when shooting under average daylight and flash illumination, approximately 5500K.

Dedicated Flash
A fully automatic flash that works only with specific cameras. Dedicated flash units automatically set the proper flash sync speed and lens aperture, and electronic sensors within the camera automatically control exposure by regulating the amount of light from the flash.

Definition
The clarity of detail in a photograph.

Dense
Describes a negative or an area of a negative in which a large amount of silver has been deposited. A dense negative transmits relatively little light.

Densitometer
An instrument used for measuring the optical density of an area in a negative or print.

Density, Image Density
Build up of silver deposits in a particular area produced by exposure and development. The more silver present in a shadow, the more the image density. Conversely, the less silver deposit in the highlights, the less the image density. Technically, density is measured in terms of the logarithm of opacity.

Depth of Field
The amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in a photograph. Depth of field depends on the lens opening, the focal length of the lens, and the distance from the lens to the subject. The zone of acceptable sharpness in a picture extending in front of and behind the plane of the subject, that is most precisely focused by the lens. It can be controlled by varying three factors; the size of the aperture; the distance of the camera from the subject; and the focal length of the lens. If the photographer decrease the size of the aperture, the depth of field increases; If the photographer focuses on a distant subject, depth of field will be greater than if the photographer focused on a near subject; and if he/she fitted a wide-angle lens to the camera, it would give the photographer greater depth of field than a normal lens viewing the same scene.

Depth of field scale
Scale on a lens barrel showing the near and far limits of depth of field possible when the lens is set at any particular focus and aperture.

Depth of Focus
The distance range over which the film could be shifted at the film plane inside the camera and still have the subject appear in sharp focus; often misused to mean depth of field.

Developer
Chemical solution used to convert the invisible silver halide crystals in the film emulsion into visible metallic silver.
Development
1. The entire process by which exposed film or paper is treated with various chemicals to make an image that is visible and permanent.
2. Specifically, the step in which film or paper is immersed in developer.

Developing Tank
A light tight container used for processing film.

Diaphragm
Lens opening. A perforated plate or adjustable opening mounted behind or between the elements of a lens used to control the amount of light that reaches the film. Openings are usually calibrated in f-numbers.

Dichroic head
An enlarger head that contains yellow, magenta, and cyan filters that can be moved in calibrated stages into or out of the light beam to change the colour balance of the enlarging light.

Diffraction
When light is obstructed by an object and the wave front is changed, interference occurs between components of the altered wave front. The pattern formed by interference is called the diffraction pattern. Many components are designed to yield very specific diffraction effects (diffractive optics, gratings). Other components attempt to counteract this process to determine more information about the obstructing medium (electronic imaging).

Diffraction filter
A colourless filter inscribed with a network of parallel grooves. These break white light up into its component colours, giving a prism-like effect to highlights.

Diffused light
Light that has lost some intensity by being reflected or by passing through a translucent material. Diffusion softens light, eliminating both glare and harsh shadows, and thus can be of great value in photography, notably in portraiture.

Diffuser
A material that softens light passing through it. The effect is to soften the character of light. The closer a diffuser is to a light source the less it scatters light.

Diffusing
Softening detail in a print with a diffusion disk or other material that scatters light.

Diffusion-Condenser Enlarger
An enlarger that combines diffuse light with a condenser system, producing more contrast and sharper detail than a diffusion enlarger but less contrast and blemish emphasis than a condenser enlarger.

Diffusion Enlarger
An enlarger that scatters light before it strikes the negative, distributing light evenly on the negative. Detail is not as sharp as with a condenser enlarger; negative blemishes are minimized.

Dilution
The reduction in the strength of a liquid by mixing it with an appropriate quantity of water.

Dioptre
Optical term for the power of a lens. Photographically, it is typically used to indicate the magnification and focal length of close-up lenses.

Dioptre correction
This is like a focus adjustment that matches the focus of the camera's optical viewfinder to the user's eyesight. This way, users don't have to wear their glasses when using the camera. As some of the viewfinders are quite small and difficult to use with your glasses on dioptre correction can be a welcome option for eyeglass wearers.

Direct positive
A high contrast positive image slide made only from camera ready originals with no negative required.

Dispersion
Light rays of different wavelengths deviate different amounts through a lens causing a rainbow effect around points and edges.

Distortion
A phenomenon in which straight lines are not rendered perfectly straight in a picture. There are two types of distortion--barrel distortion and pincushion distortion. Distortion cannot be improved by stopping down the lens.

Diverging lens
A lens which causes rays of light coming from the subject to bend away from the optical axis.

D/log E curve
A graph of density (D) against the logarithm of exposure (log E) Used in sensitometry to compare the sensitivity of different emulsions to light.

D-max
Maximum density. The greatest density in an image. Also, the greatest density possible for a particular film or paper.

D-min
Minimum density. The smallest density in a image. Also, the smallest density possible for a particular film or paper.

Dodging
Holding back the image-forming light from a part of the image projected on an enlarger easel during part of the basic exposure time to make that area of the print lighter. Other tonal techniques include burning, flashing, toning, and bleaching.

Double Exposure
Two pictures taken on one frame of film, or two images printed on one piece of photographic paper.

Drying cabinet
Is a vented cabinet equipped with suspension clips for drying films.

Drying marks
Are marks on the film emulsion caused by uneven drying and resulting in areas of uneven density, which may show up in the final print.

Dry mounting tissue
A thin paper coated with adhesive on both sides for permanently adhering a photograph to a support. The adhesive is softened by heat and hardens when it cools.

Dupes
A copy of a slide or transparency made without an inter-negative or special duplicating film. Frequently used as an intermediate image for other print subjects.

DX Data Exchange
Electrical coding system employed in 35 mm format film that communicates film speed, type and exposure length to the camera.

E-6
Chemical processing system for most colour-reversal (slide) film.

Easel
A device to hold photographic paper flat during exposure, usually equipped with an adjustable metal mask for framing.

Edge numbers
The reference numbers printed by light at regular intervals along the edge of 35mm and roll films during manufacture.

EI
see exposure index

Emulsion
Micro-thin layers of gelatine on film in which light-sensitive ingredients are suspended; triggered by light to create a chemical reaction resulting in a photographic image.

Emulsion Side
The side of the film coated with emulsion. In contact printing and enlarging, the emulsion side of the film-dull side-should face the emulsion side of the photo paper-shiny side.

Enlargement
A print that is larger than the negative or slide; blow-up.

Enlarger
A device consisting of a light source, a negative holder, and a lens, and means of adjusting these to project an enlarged image from a negative onto a sheet of photographic paper.

Existing Light
Available light. Strictly speaking, existing light covers all natural lighting from moonlight to sunshine. For photographic purposes, existing light is the light that is already on the scene or project and includes room lamps, fluorescent lamps, spotlights, neon signs, candles, daylight through windows, outdoor scenes at twilight or in moonlight, and scenes artificially illuminated after dark.

Exposure
The quantity of light allowed to act on a photographic material; a product of the intensity (controlled by the lens opening) and the duration (controlled by the shutter speed or enlarging time) of light striking the film or paper.

Exposure compensation
Many camera have the ability to force the camera to overexpose or underexpose an image during capture. This can be done for effect or to compensate for some particular lighting situation. This is often referred to as EV compensation.

Exposure factor
A figure by which the exposure indicated for an average subject and/or processing should be multiplied to allow for non-average conditions. Usually applied to filters. Occasionally to lighting. Processing, etc Not normally used with through-the-lens exposure meters.

Exposure index ( EI )
A film speed rating similar to an ISO rating abbreviated EI.

Exposure Latitude
The range of camera exposures from underexposure to overexposure that will produce acceptable pictures from a specific film.

Exposure Meter
An instrument with a light-sensitive cell that measures the light reflected from or falling on a subject, used as an aid for selecting the exposure setting. The same as a light meter.

Expiry date
The date stamp on most film boxes indicating the useful life of the material in terms of maintaining its published speed and contrast.

Extension tubes
Tubes made from metal and, more frequently, plastic inserted between the lens and the camera, thereby making the lens to film distance greater. The result is increased magnification for close-up photography.

Extension bellows
Device used to provide the additional separation between lens and film required for close-up photography.

EV
see exposure value

Eye light
A highlight in the eye or the small light placed near the camera to produce it.

Eyepiece shutter
A built-in device that prevents light from entering the viewfinder eyepiece.

Factor
See filter factor

Fading
The loss of or change of colour density, generally accelerated by exposure to sunlight.

Falloff
Decrease in the intensity of light as it spreads out from the source.

Fast film
Is film which has an emulsion that is very sensitive to light. These film have high ISO ratings.

Fast lens
Is a lens with a wide maximum aperture ( low f number ).

Fibre Based Paper
Photographic paper without a resin (plastic) coating. Processing times are longer than for other papers, but the paper probably has more archival permanence than resin coated papers.
(See other paper types: variable contrast, graded contrast, resin coated.)

Field curvature
A lens aberration or defect that causes the image to be formed along a curve instead of on a flat plane.

Fill-In Light
Additional light from a lamp, flash, or reflector; used to soften or fill in the shadows or dark picture areas caused by the brighter main light. Called fill-in flash when electronic flash is used.

Fill-flash
A technique that uses flash illumination as a supplement to ambient light. Useful when photographing subjects that are backlit, with very high-contrast lighting or in shadow.

Film
A photographic emulsion coated on a flexible, transparent base that records images or scenes.

Film base
Flexible support on which light sensitive emulsion is coated.

Film Characteristic Curve
This curve describes a graphical relationship between the logarithm of the exposure value (horizontal axis) and density (vertical axis) of film. Each brand of film may exhibit a different characteristic curve.

Film clips
Metal or plastic clips used to prevent the curling of the film during the drying.

Film holder
A light-tight, removable device for holding film on many medium-format. This allows the photographer to preload the film so he can quickly change rolls of film.

Film leader
Length of protective film at the beginning of a roll of unexposed or processed film.

Film plane
The plane on which the film lies in a camera. The camera lens is designed to bring images into focus precisely at the film plane in a camera to ensure correctly exposed pictures.

Film pressure plate
A part of the camera back which, when closed against the film guide rails, creates a very precise tunnel in which the film is flatly positioned for sharpness.

Film Speed
The sensitivity of a given film to light, indicated by a number such as ISO 200. The higher the number, the more sensitive or faster the film. Note: ISO stands for International Standards Organization.

Filter
A coloured piece of glass or other transparent material used over the lens to emphasize, eliminate, or change the colour or density of the entire scene or certain areas within a scene.

Filter factor
The increased exposure needed to compensate for the amount of light absorbed by a filter. A factor of two indicates you need to give the film one stop more exposure; a factor of three needs two stops and a factor of six needs three stops more.

Filter pack
Several filters used together, as in a enlarger for colour printing or when duplicating slides, in order to obtain the best or desired colour in the image.

Fine grain
Film or developer that produces images in which areas of uniform tone appear smooth, with no clumping of the silver particles that form the image.

Fine grain developers
Are film developers which help to keep grain size in the photographic image to a minimum.

Finder
A viewing device on a camera to show the subject area that will be recorded on the film. Also known as viewfinder and projected frame.

Fisheye lens
Extreme wide-angle lens with an angle of view exceeding 100 degree and sometimes in excess of 180 degree. depth of field is practically infinite and focusing is not required.

Fixed-Focus
Describes a non-adjustable camera lens, set for a fixed subject distance.

Fixed-Focus Lens
A lens that has been focused in a fixed position by the manufacturer. The user does not have to adjust the focus of this lens.

Fixer
A chemical solution (sodium thiosulfate or ammonium thiosulfate) that makes a photographic image sensitive to light. The fixer stabilizes the emulsion by converting the undeveloped silver halides into water-soluble compounds, which can then be dissolved away. Also called hypo.

Fixing Bath
A solution that removes any light-sensitive silver-halide crystals not acted upon by light or developer, leaving a black-and-white negative or print unalterable by further action of light. Also referred to as hypo.

Flare
The soft effect visible in a picture resulting from stray light which passes through the lens but is not focused to form the primary image. Flare can be controlled by using optical coating, light baffles and low reflection surfaces , or a lens hood.

Flash
A brief, intense burst of light from a flashbulb or an electronic flash unit, usually used where the lighting on the scene is inadequate for picture-taking.

Flash factor
Is a number which provides a guide to correct exposure when using Flash. See also Guide number

Flash meter
A device for measuring the light coming from a electronic flash and indicating the appropriate aperture for correct exposure. Some flash meter can also measure the ambient light.

Flash range
The maximum distance from which a flash can effectively illuminate a subject. Most built-in flashes are effective to about 12-15 feet. Range varies by brand, so check the specification carefully.

Flash sync
A special socket on a camera that allows the attachment of an auxiliary strobe light for flash pictures. It is synchronized to the camera's shutter so the light goes off at the right time.

Flashing
Pre-exposing the paper to a very diffused white light in order to reduce the contrast level between the highlights and shadows and extend the tonal range. Other tonal techniques include burning, dodging, toning, and bleaching.

Flat
Too low in contrast. The range in density in a negative or print is too short.

Flat Lighting
Lighting that produces very little contrast or modeling on the subject plus a minimum of shadows.

Floodlight
An electric light designed to produce a broad, relatively diffused beam of light.

f-Number or f-Stop.
A number that indicates the size of the lens opening on an adjustable camera. The common f-numbers are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. The larger the f-number, the smaller the lens opening. In this series, f/1.4 is the largest lens opening and f/22 is the smallest. Also called f-stops, they work in conjunction with shutter speeds to indicate exposure settings.

Focal Length
The distance between the film and the optical centre of the lens when the lens is focused on infinity. The focal length of the lens on most adjustable cameras is marked in millimetres on the lens mount.

Focal plane
The plane on which the image of a subject is brought to focus behind the lens. To produce a sharp picture, the lens must be focused so that this place coincides with the plane on which the film sits. Also called the film plane.

Focal-Plane Shutter
An opaque curtain containing a slit that moves directly across in front of the film in a camera and allows image-forming light to strike the film.

Focal point
The point on a focused image where the rays of light intersect after reflecting from a single point on a subject.

Focus
Adjustment of the distance setting on a lens to define the subject sharply.

Focusing
System of moving the lens in relation to the image plane so as to obtain the required degree of sharpness of the film.

Focusing cloth
A dark cloth used in focusing a view camera. The cloth fits over the camera back and the photographer's head to keep out light and to make the ground glass image easier to see.

Focus Range
The range within which a camera is able to focus on the selected picture subject - 4 feet to infinity - for example.

Focusing screen
Used for focusing on a subject or composing a picture; the focusing screen is located at a position equivalent to that of the film plane. To provide dispersion, a matte field made of specially ground glass or plastic is generally used for focusing screens.

Fog
An overall density in the photographic image cause by unintentional exposure to light or unwanted chemical activity.

Fogging
Darkening or discolouring of a negative or print or lightening or discolouring of a slide caused by
exposure to non-image-forming light to which the photographic material is sensitive, too much handling in air during development, over-development, outdated film or paper, or storage of film or paper in a hot, humid place.

Forced Development
(See Push-processing)

Foreground
The area between the camera and the principal subject.

Frame
One individual picture on a roll of film. Also, tree branch, arch, etc., that frames a subject.

Fresnel
Pattern of a special form of condenser lens consisting of a series of concentric stepped rings, each ring a section of a convex surface which would, if continued, form a much thicker lens. Used on focusing screens to distribute image brightness evenly over the screen.

Front lighting
Light shining on the side of the subject facing the camera.

G curve
Is an average gradient of a characteristic curve, describing similar characteristics to gamma, but measuring the slope from a line joining the lower and upper of the curve actually used in practice.

Gelatine
The medium used on photographic materials as a means of suspending light-sensitive silver halides.

Gelatine filter
Are filters cut from dyed gelatine sheets and held in front of the lens or studio light.

Ghost image
In time exposure photography, an object that is only partially recorded on the film and therefore has a translucent, ghost-like appearance. Some people also refer to " flare " as a ghost image.

Glossy
Describes a printing paper with a great deal of surface sheen. Opposite: matte.

Gradation
A smooth transition between black and white, one colour and another, or colour and no-colour.

Graded Contrast
Printing paper containing a single layer of emulsion of a specific contrast range. To change the overall contrast level, you must change to another grade of paper. (See other paper types: variable contrast, resin coated, fibre based.)

Grades, Paper Grades
A classification system for specifying the degree of paper contrast, ranging from 0 (very soft) to 5 (very hard).
(See paper types: variable contrast, graded contrast, resin coated, fibre based.)

Gradient
A smooth spread between colours.

Grain
Clumps of silver-halide grains in film and paper that constitute the image. These grains are produced both in the exposure process (film grain) and in the development process (paper grain). Unlike film, the grain in printing paper is largely responsible for the image tone. Graininess is most noticeable in even, mid-tone areas of a print.

Graininess
The sand-like or granular appearance of a negative, print, or slide. Graininess becomes more pronounced with faster film and the degree of enlargement.

Grey card
A card that reflects a known percentage of the light falling on it. Often has a grey side reflecting 18 percent and a white side reflecting 90 percent of the light. Used to make accurate exposure meter readings (meter base their exposures on a grey tone of 18 percent reflectance) or to provide a known grey tone in colour work.

Grey level
A shade of grey assigned to a pixel. The shades are usually positive integer values taken from the grey-scale. In a 8-bit image a grey level can have a value from 0 to 255.

Grey scale
An image type that contains more than just black and white, and includes actual shades of grey. In a greyscale image, each pixel has more bits of information encoded in it, allowing more shades to be recorded and shown. 4 bits are needed to reproduce up to 16 levels of grey, and 8 bits can reproduce a photo-realistic 256 shades of grey.

Greyscale image
An image consisting of up to 256 levels of grey, with 8 bits of colour data per pixel.

Ground glass
A piece of glass roughened on one side so that an image, focused on it can be seen on the other side.

Guide number
A number used to calculate the f-setting (aperture) that correctly exposes a film of a given sensitivity (film speed) when the film is used with a specific flash unit at various distances from flash to subject. To find out the f-setting, divide the guide number by the distance.