GLOSSARY

A-D


A


Adobe Photoshop Professional-standard image manipulation software package. Although it is costly and requires a powerful computer, the program offers a wide range of techniques and effects. Suitable for PCs and Macs.

AE See Autoexposure.

Aerial perspective Illusion of depth and distance in a photograph due to the light- scattering effect of atmospheric haze.

AF See Autofocus.
Ambient light See Available light.

Analogue A non-digital recording system where the strength of the signal is in direct proportion to the strength of the source.

Angle of view Most widely separated parts of a scene that a lens is capable of resolving into an acceptable image on a piece of film. The angle of view varies according to the focal length of the lens and the camera format.

Anti-aliasing A method of smoothing diagonal lines in digital images, to avoid a staircase, or stepping, effect created by the individual pixels.

Antihalation layer Coating of dye on the back of films that absorbs light. Without this layer, light would be reflected back from the film base and through the emulsion, creating ill-defined haloes around sources of bright light in the image.

Aperture Circular opening within a lens that determines the amount of light that is allowed to pass through to reach the film. On all but the simplest of cameras, the size of the aperture can be varied by a diaphragm, which is set to different-sized openings, known as “stops,” calibrated in f-numbers.

Aperture priority Type of semi-automatic exposure system whereby the photographer sets the aperture and the camera selects the corresponding shutter speed to ensure correct exposure of the scene.

APS (Advanced Photo System) Miniature film format used for compact cameras and some SLRs. Film is automatically loaded from the cassette by the camera, and is returned in the cassette after processing. An indicator shows whether the film is unused, partly used, completely used, or developed. A five-digit reference number on the cassette is also printed on the back of prints to allow you to identify negatives. The image area of the format is 30.2 x 16.7mm, but the user can 

choose from three print sizes at the time of shooting. Information about each picture is marked invisibly on the film's magnetic strip, and this data is used during printing.

Archival Any process or material that is specifically designed to significantly improve the life expectancy of the image.

Array The arrangement of image sensors in a digital device.

Artefacts Unwanted information in a digital image, caused by limitations in the recording process.

Attachment A digital file attached to an e-mail.

Autoexposure Camera system designed to set the size of the aperture and/or the shutter speed, to ensure correct exposure of a scene. Film speed is also taken into account.

Autofocus A system where the lens is adjusted automatically by the camera to bring the image into sharp focus.

Autofocus illuminator System used in some cameras to assist autofocus in low light situations. A red pattern is projected onto the subject, which enhances the contrast-detection function of the autofocus, allowing the lens

to be adjusted correctly.

Available light Light that is normally available in a scene, such as extra domestic tungsten lighting, but not including artificial light such as flash. Also known as ambient or existing light. 


B


B (Bulb) setting Shutter setting found on many cameras that holds the shutter open for as long as the release is depressed. Used for manually timing exposures that are longer than the standard shutter speeds available.

Backlight compensation control Manual exposure control found on many modern cameras that opens the aperture by a predetermined amount to compensate when the main subject is backlit. Most exposure- measuring systems tend to underexpose a backlit subject because the side of the subject facing the lens is in shadow.

Backlighting Lighting that illuminates the subject from the rear. See also Backlight compensation control.

Back-up Copy of a digital file, kept in case of damage to or deletion of the original.

Ball-and-socket head Simple type of camera- mounting system found on some tripods. It consists of a ball that can be rotated in a cup- shaped fixture, allowing sideways and up-and- down camera movements. See also Tripod.

 

Barn doors Set of four hinged metal flaps on a frame that fit around a spotlight. Moving the flaps in or out of the light beam controls the spread of light.

Barrel distortion Design fault, usually associated with wide-angle lenses, that causes vertical lines near the edges of the frame to bulge outward.

Bellows See Extension bellows.

Between-the-lens shutter Shutter system on most compact cameras that is built within the lens itself. See also Focal-plane shutter.

Bit The basic unit from which any digital piece of data is made up. Each bit has a value of 0 or 1. Digital files are usually measured in bytes, which are each made up of 8 bits.

Bleed A picture that is printed or cut so that the image extends to the edge of the paper.

Bluetooth Wireless connection system used to link different computer peripherals and digital devices using radio signals.

Blur Unsharp image area caused by camera or subject movement, inaccurate focusing, or a limited depth of field.

Bounced flash Light from a flash that is first directed at a surface, such as a wall, ceiling, or reflector, before it reaches the subject. This creates a broad, soft area of lighting.

Bracketing Taking a series of photographs of the same scene with each frame at a different exposure setting. Useful when you want to select slightly darker or lighter prints than the exposure system would normally produce, or when it is difficult to judge the best exposure.

Burning-in Photographic printing term used to indicate those parts of an image that would benefit from extra exposure. Parts of the image not requiring burning-in must be shaded from the enlarger light during this process. The procedure can be mimicked by most digital manipulation programs.

Byte Standard unit for measuring memory capacity of digital devices. Each byte can have one of 256 values, and is equal to 8 bits


C


Cable release Mechanical or electrical device used to trigger the shutter. Useful if a camera is mounted on a tripod, as it ensures that the camera is stable at the moment of exposure.

Cassette Metal or plastic holder for 35mm and APS film.

Catadioptric lens See Mirror lens.
CC filter Abbreviation for Color conversion 

 

filters – pale color filters designed to provide small changes in color balance when using color slide film.

CCD (Charge Coupled Device) An imaging sensor used in digital cameras, found at the focal plane. It converts the focused image into an electrical signal. See CMOS sensor.

Center-weighted metering Type of exposure-measuring system that assumes the subject is placed in the center of the frame so weights the exposure in favor of that area.

Chromatic aberration Lens fault that causes the different wavelengths of light to focus on slightly different planes. It appears as a series of different-colored fringes around the subject. Occurs with some cheap camera lenses, and lenses with long focal lengths.

Clip test Small length of film clipped from the beginning of an exposed roll. This is processed in advance so that processing times can be adjusted if necessary for the rest of the film.

Clone tool Facility on many digital image manipulation programs that allows you to replace an area of the image with a copy taken from another part of the image. Extensively used for removing blemishes, dust marks and unwanted subject matter from a digital photograph.

CMOS (Complementary Metal Oxide Semiconductor) An imaging sensor used in digital cameras similar to a CCD sensor. It is found at the focal plane, and converts the focused image into an electrical signal.

CMYK Cyan, Magenta, Yellow, and Black – the four primary inks used in commercial and desktop printing to produce full-color images. Digital photographs and scans are recorded in RGB (red, green, and blue), but can be converted to the CMYK color space using imaging editing software. It

is not, however, necessary to convert before printing.

Color balance The matching of film or imaging chip settings to ensure that white and grey tones appear in a picture as they would to the human eye. With color film, color balance can be changed using filters. With digital cameras, color balance is changed electronically using the white balance system.

Color-cast Unwanted color tint on an image, usually created by incorrect color balance or by a reflection from a strongly-colored object.

Color depth The amount of color information in a digital image. 8-bit color offers 256 distinct colors, 16-bit color offers over 65,000 colors, whilst the human eye is capable of distinguishing over 16-million colors (32-bit color). 

Color gamut The range of colors that can be displayed by a computer screen, or printed by a printer. This range of possible colors may well be different for both – and different from those recorded in the digital file.

Color management A system that warns you of color gamut problems, and helps to ensure that the colors that are printed look the same as those you see on screen.

Color temperature Measurement of the color of light, often expressed in Kelvin (K). The human eye adjusts for the color temperature of different light sources without us realising. A digital camera can make electronic adjustments using its white balance system. When using color film, if accurate color balance is essential, correct filtration is often necessary when shooting or printing.

Compact A type of camera that has a shutter mechanism built into the lens. Compacts use point-and-shoot designs that are easy to carry around. Many have built-in zooms and either record images digitally or on film.

Complementary colors In a photographic context, this term refers to the colors yellow, magenta, and cyan, which are complementary to the primary colors blue, green, and red. Colors are complementary to one another if, when mixed in the correct proportions, they form white or gray.

Contact sheet A print with the images from the same roll of film exactly the same size as the negatives. Contacts are produced by placing the negatives in contact with a sheet of photographic printing paper, pressing them down under a piece of glass, and exposing them to light.

Continuous AF Autofocus setting where the focus is constantly adjusted up until the moment the shutter is fired. Useful for moving subjects, where it is inappropriate for the focus distance to be locked once correct focus is initially found.

Continuous tone Term used in black and white photography to describe a negative or print that has gradations of tone from black to white, which correspond to the different tones of the original subject.

Contrast range A measurement of the difference in brightness between the darkest and lightest part of an image. Films and image sensors are capable of successfully dealing with differing, but generally limited, contrast ranges.

Contre jour Another term for backlighting.

Converging verticals An effect usually associated with a wide-angle lens that occurs when the film plane and the subject are not parallel. This results in the vertical sides of a tall building appearing to converge when the camera is tilted back to include the top.

Cropping Removing unwanted parts of an

image by enlarging only part of the frame during printing or digital manipulation. 


D


Daylight-balanced film Film designed to reproduce correct subject colors when exposed in daylight or by the light of electronic flash or blue flash cubes. See also Tungsten-balanced film.

Dedicated flash Type of flashgun designed to be used with a specific camera or range of cameras. Once attached to the camera, the flashgun effectively becomes an extension of that camera’s circuitry, controlling shutter speed, receiving film speed information, and using the exposure meter.

Depth of field Zone of acceptably sharp focus extending in front of and behind the point of true focus. Depth of field varies depending on the aperture selected, the focal length of the lens (or zoom setting), and the focused distance. Depth of field is increased if a smaller aperture is set, a lens with a shorter focal length is selected, or the further the subject focused on is away from the camera.

Depth of field scale Pairs of f-numbers engraved on a lens barrel that indicate the effective depth of field surrounding a subject when the lens is focused on the subject and the desired aperture has been selected.

Depth of focus Distance that the film plane can be moved without requiring the camera to be refocused.

Diaphragm Adjustable aperture of a lens. The size of the aperture affects the amount of light reaching the film, and the depth of field.

Diffuser Any material that is used to scatter and soften light.

Digital manipulation Any alteration to a digital image on a computer that changes its appearance. Digital manipulation software provides a range of tools and techniques that are similar to those of the traditional darkroom, hence the fact that digital manipulation processes are often referred

to as the digital darkroom.

Dodging Masking selected areas of the image at the printing stage to reduce exposure in that area in relation to the rest of the image. A process that is often recreated with tools available during digital manipulation.

Downrating Exposing film as if it were less sensitive to light than its ISO rating indicates. Allowances for downrated film have to be made during development. Also known as pulling. 

dpi (dots per inch) A measure of the

resolution of a printer or other digital device.

DPOF (Digital Print Order Format) Facility available on some digital cameras that allows users to mark the images that they wish to have processed into prints.

Driver A piece of software that is used by a computer to control and communicate with a printer, scanner, or other peripheral.

DX coding Black and silver markings on a 35mm film canister that can be read by many cameras. These usually only tell the camera the film's ISO speed (its sensitivity to light), but the code can also communicate the length of the roll and its exposure latitude.

Dye sublimation Printing method used to make high-quality prints from digital image files. The results look and feel very similar to traditional photographic prints.