Digital photography glossary

By Staff writers on 02 July 2007

Having problems with certain camera jargons? Fret not. We have compiled a list of the common terms and definitions used in digital photography.

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24-bit image	This type of digital image has pixels that are allocated 24 bits of storage (usually with 8 bits for red, 8 for blue, and 8 for green), allowing representation of 256 by 256 by 256 (or more than 16 million) different colour combinations.
8-bit image	This is a digital image composed of as many as 256 possible colours or shades of grey.

acquire	The act of transferring an image from a digital camera to a computer or of importing it from another source into a program, such as Adobe Photoshop.
adaptive palette	This is a set of colours selected to represent, as closely as possible, the colors in the original source image.
AF sensor	The sensor used to detect and help correct the focus in cameras equipped with an autofocus function.
algorithm	A formula or set of steps for solving a particular problem.
ambient	A term used to describe the lighting or illumination in a scene that does not originate from any specific light source, direction, or object in the scene.
angle of view	The width of the area a lens can see; measured in degrees.
aperture	The opening behind a camera lens through which light passes to make a photographic exposure. The range of sizes to which the aperture can be set is described by the f-stop numbers (for example, f/1.8 through f/22). Lower numbers indicate larger aperture sizes; the larger the aperture, the more light enters the camera.
artifact	Misinterpreted information from a JPEG or a similarly compressed image; includes defects that appear in an image as colour flaws or skewed lines.
artifical light	Light from a man-made source, usually restricted to studio photo lamps and domestic lighting.
ASA	See Speed
aspect ratio	This is the ratio of height to width of an image, computer screen, LCD screen, television, or other medium. Images will become distorted if they are forced into a different aspect ratio during enlargement, reduction, or transfers.
autofocus	Camera feature that uses an infrared (IR) beam or sonar to set its focus.
available light	The light present in an area without the addition of a strobe or a floodlight.
AVI	Short forAudio Video Interleave; the file format for Microsoft's Video for Windows standard, one of several video technologies used on personal computers. (Others include MPEG, RealMedia, and QuickTime.) In AVI, picture and sound elements are stored in alternate interleaved chunks in the file so that they play in sync

backlighting	Illumination of the subject of a photo from behind using either artificial or natural light.
bas-relief	In digital photography, this refers to an effect produced with a Photoshop filter, which makes an image appear to be slightly raised off the surface.
bit	Short for binary digit, which is a computer value of zero or one, on or off; this is the most basic language used by computers.
bit depth	Refers to the colour or grayscale of an individual pixel. A pixel with 8 bits per colour produces a 24-bit image; 8 bits multiplied by three colours -- red, green, and blue -- equals 24 bits. CCDs are colored in a pixel-by-pixel method, using the following guidelines: 32-bit colour (true colour) contains billions of colours; suitable only for high-end use 24-bit colour (true colour) contains 16.7 million colours 16-bit colour (high colour) has 32,000 colours; the accepted standard for Macintosh 8-bit colour has 256 colours; this is the basic setting for Windows 8-bit grayscale has 256 shades of grey 4-bit is 64 colours or greys 2-bit is black and white
bitmap	A means of describing and displaying a graphic image onscreen, pixel by pixel.
black point	This is the colour that produces colour values of 0, 0, 0 for each of the RGB components when scanned or digitised. Normally, the black point is 0 percent neutral reflectance or transmittance.
bleed	Refers to printing that extends beyond the edge of a page so that the ink meets the edge after the page is trimmed.
blowup	An enlargement of a picture; or the process of enlarging a picture (to blow up).
blur	A photographic effect, either intentional or unintentional, that produces an picture with a loss of image sharpness.
bmp file	A Microsoft Windows bitmap graphics file that has the extension .bmp.
bounce light	Light that is bounced off a reflective surface, such as any of the following: a white card, an aluminised reflector, a wall, or the ceiling.
box camera	Simple camera consisting of a lens, a shutter, a media holder, and a viewfinder.
burn in	To darken a small area of a picture; named after the process done in a darkroom, where all but the affected area is masked in order to give extra exposure to only the unmasked area.
byte	Short for binary term; a unit of storage capable of holding a single character; on almost all modern computers, a byte is equal to eight bits.

card	Memory chip that can be used to store images and data. Various forms currently exist, the most popular of which is Secure Digital (SD). Other formats include Secure Digital High Capacity (SCHC), CompactFlash, Sony Memeory Stick and xD-Picture Card.
catchlight	A light placed so as to reflect tiny white dots in the eyes of a portrait subject.
CCD	Short for charged coupled device; a mechanism that converts light into a proportional (analog) electrical current; the two main types of CCD are linear arrays, used in flatbed scanners and digital copiers, and area arrays, found in camcorders, digital cameras, and the like.
CGM	Short for computer graphics metafile; this is an image file format designed to handle a wide range of image types.
chroma	A quality of colour, combining hue and saturation.
chromatic abberation	Also known as colour fringing, this problem is caused when the camera lens do not focus the different wavelengths of light onto the exact same focal plane. It usually happens around subjects with a wide contrast and around the edges of the image in wide-angle shots.
close-up lens	Lens that allows close photography; also called a macro lens.
CMYK	Short for cyan, magenta, yellow, and black; colour model that defines the amount of colour by percentage.
codec	Short for compressor/decompressor; a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both.
colour balance	Means of compensating for too much of one colour in a photo by adding that colour's opposite; for example, if a photo has too much blue, adding a larger percentage of yellow would help achieve a balance.
colour temperature	A means of measuring the relative redness or blueness of a light source; measured in degrees kelvin (K); higher numbers produce bluer light. Typical incandescent bulbs are approximately 3,200 degrees K, while daylight is about 6,500 degrees K.
colour wheel	The circular relationship of all colours based on the frequencies of light at each colour.
compression	The reduction of data to reduce the size of a file; compression can be lossy (for example, JPEG images) or lossless (for instance, TIFF images); lossy images have a greatly reduced file size.
continuous tone	An image where brightness appears consistent and uninterrupted; each pixel in a continuous-tone image uses at least one byte for its red, green, and blue values. This allows 256 density levels per colour or more than 16 million colour mixtures.
contrast	A measure of the rate of change of brightness in an image; high contrast suggests content consisting of dark blacks and bright whites; medium contrast implies a good spread from black to white; and low contrast implies a small spread of values from black to white.
crop	The action of trimming away the unwanted parts of an image.
cropping tool	An applet found within photo-editing software that allows one to trim away unwanted parts of an image.
cyan	One of the three primary colours in colour prints (coupled with magenta and yellow).

daguerreotype	Photo process developed by Joseph Daguerre that produces an extremely grainy, gray or sepia-toned (brownish) image; presently used to artificially convey age.
dark voltage	Also called dark current, this is the voltage from a CCD when no light is incident on the CCD.
definition	The clarity of detail in an image; dependent upon resolution (number of pixels) and contrast.
depth of field	Means of describing the area of a photograph that is in focus.
derived image	An image that was created from another image.
diaphragm	This is another term for aperture.
diffusion dithering	A method of dithering that distributes pixels randomly rather than using a set pattern.
digital	Any system or device that stores information in a format suitable for computers to read; digital information is stored in bits, where each bit is represented as on/off or one/zero.
digital camera	A device that captures an image on a CCD (charged coupled device) so that the image file can be downloaded to and manipulated by a computer; does not use conventional film.
digital image	An image composed of pixels.
digitisation	The process of converting analog information into a digital format for use on a computer.
disc	Term used to describe optical storage media (laserdisc, compact disc).
disk	Term used to describe magnetic storage media (floppy disk, hard disk).
dithering	A method of simulating many colours or shades of grey by combining only a few; for instance, red and blue dots are dithered to make purple. Dithering allows a photo with millions of colours to be displayed on a 256-colour monitor and printed on a 4-colour printer.
dodging	Also called holding back; in traditional darkroom work, the hand of the developer or a piece of cardboard would be used to block light passing from the enlarger to the print, thus lessening the exposure in only specific parts of the picture. Digitally, the effect is to lighten part of the image without affecting the rest.
DPI	Short for dots per inch; a measurement based on the dot density of either a printer's resolution or a video monitor image. For example, most laser printers have a resolution of 300 dpi, and most video monitors are set at about 72 dpi.
duotone	An offset-printed image created with two different colours of ink.
dynamic range	Refers to the gradations of light and dark that a digital camera can capture where details are neither washed out by light nor concealed by shadows.

electric flash	Refers to the gradations of light and dark that a digital camera can capture where details are neither washed out by light nor concealed by shadows.
EPS	Short for Encapsulated PostScript; a type of graphics file that produces a high-quality image.
export	A software function that allows you to save a copy of information produced in one format into a file of another format.
exposure	The amount of light that reaches the film; the combination of f-stop and shutter speed, which controls the amount of light that passes through the lens to the film.
exposure compensation	In photography, exposure compensation allows you to intentionally under- or overexpose a shot to achieve a particular effect.
exposure shift	See exposure compensation.
exposure meter	A device that measures available light and computes correct exposure.

fibre-optics	An optical system that uses glass or transparent plastic fibers as light-transmitting media; a fibre-optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves.
file format	A format for encoding visual information in a file; some common image file formats include TIFF, PICT, and EPS files.
fill	This is a process that allows you to alter a selected area of an image with a computer graphics program, covering or combining it with a gray shade, a colour, or a pattern.
film recorder	A device used to record a digital image onto photosensitive film.
filmstrip	This is a file format developed by Adobe allowing sequential images from a movie to be transferred between Premiere and Photoshop.
filter	A tinted-glass or plastic lens that fits onto the camera lens to alter the visual field.
fish-eye lens	This is an extremely wide-angle lens. A fish-eye lens magnifies the parts of the image near the centre of the image and reduces the parts that are far away from the centre.
fixed-focus lens	A lens in which the focus is preset and is not adjustable.
flare	The reflected light from lens elements that appears as a non-uniform haze or as bright spots on the film. This usually happens when a bright light directly enters the lens.
flash card	A memory card that works with the flash memory, allowing the camera to retain data after the system has been turned off.
flash memory	A memory chip that has the ability to retain image data even after the host system has been shut off; this feature insures that, even if the digital camera's batteries die, the image data will remain stored in the camera's memory.
FlashPix	The popular trade name for a multiresolution image-file format developed by Kodak, Hewlett-Packard, Microsoft, and Live Picture.
flatbed scanner	This is an optical scanner in which the original image remains stationary while sensors scan the material from beneath the image.
focal length	The distance from the surface of the lens to the focal point or centre point at which light rays converge; the focal length determines the length of the lens.
focal range	This refers to the entire area that is in focus.
focus	To move the lens or film/image sensor in order to record a sharp image.
frame grabber	A photo-editing program tool used to move menus and palettes around on the screen.
FPX	Short for flashpix; an emerging World Wide Web standard file format for images.
f-stop	A means of measuring the width of the diaphragm opening, which determines how much light passes through the lens. Smaller numbers in an f-stop correspond to wider lens openings; as the f-stop reading increases in number, the lens opening decreases inversely.
full-screen image	A digital image that takes up the entire computer screen.

gamma correction	A digital image that takes up the entire computer screen.
gamut	The range of colours that can be captured or represented by a camera or graphics device.
GIF	Short for graphic image format; an image file format widely used on the Internet; provides high-quality image compression.
gradient fill	An image fill that gradually transitions from one colour to another; commonly used in graphics editors.
granularity	An image fill that gradually transitions from one color to another; commonly used in graphics editors.
grayscale	A term used to describe an image that primarily contains shades of gray, as well as black and white.
halftone	An image that is reproduced through a series of dots to simulate shades of gray in a photograph; halftone has traditionally been used in the reproduction of images for newspapers and magazines.
high-key image	A light, overexposed image, with few dark tones.
highlight	This is the lightest part of an image.
hue	The tint of a colour as measured by the wavelength of light. Hue is also represented by a position on the colour wheel.

image capture	The use of a device, such as a scanner or digital camera, to create a digital representation of an image. This digital representation can then be stored and manipulated on a computer.
image editor	A graphics program that provides a variety of special features for altering bit-mapped images for photographs and graphic images.
image processing	The manipulation of images that have been scanned or captured by a digital recording device.
image stabilisation	Image stabilisation, IS in short, helps to steady the image projected into the camera to compensate for hand shake. It differs from digital image stabilisation found in most digital video cameras as the later involves manipulation of image pixels to create a stable video image.
image stabilisation	Image stabilisation, IS in short, helps to steady the image projected into the camera to compensate for hand shake. It differs from digital image stabilisation found in most digital video cameras as the later involves manipulation of image pixels to create a stable video image.
index colour	This process minimises the number of colours and file size of a graphic image to 8-bit or less for Web publishing.
indexed colour image	Images that contain several colors or levels of grey and a palette (or colour map) that specifies the colour of each given level.
interpolation	An averaging process used to estimate an unknown image value bracketed by two or more known image values. In image processing, interpolation is used to smooth the edge lines of images when the resolution of the image is changed. Interpolation often tends to overcompensate for lost detail, and the result is a less-than-sharp image.
IR	Short for infrared.
ISO	See speed.

jaggies	This is a slang term referring to the jagged pixellisation effect that occurs in digital imaging.
JPEG	Short for Joint Photographic Experts Group; this is a highly compressed image file, which takes an area measuring 8 by 8 pixels and compresses its information to the lowest common value. JPEG images tend to be lower in quality compared to other image formats, but their minimal size frees up room when dealing with limited storage space.

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