Digital photography glossary

By Staff writers on 02 July 2007

0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


LCD	Short for liquid crystal display; a small, flat, visual screen that employs liquid crystal technology in order to display images.
leaf shutter	Located in the lens, this camera shutter utilizes a spring with the aperture control device to control the exposure time. It can be synchronised with a flash at any speed.
LED	Short for light emitting diode; an electronic device that lights up when electricity passes through it. LEDs are usually red, and are used for camera viewfinder displays, since they can be seen in the dark.
lens	An optical device that focuses light rays. In cameras, the lens is the device on the front face (or in a tube extending from the front face) that gathers the incoming light and concentrates it so that it can be directed toward the film (in an optical camera) or the imaging device (in a digital camera).
light box	A device for viewing developed film or slides. It consists of a box of backlit balanced light behind a glass or plastic surface on which the film or slides are placed for viewing.
light meter	A light-sensitive measuring device used to evaluate the amount of light focused on a subject in order to set the proper exposure.
lossless compression	This compression format minimises the size of files by creating an internal shorthand, which restores the image to its original state before compression.
lossy compression	This compression method minimises file size by eliminating unnecessary data, which causes a slight degradation of image quality.
low-key image	A dark underexposed image with few light tones.
LPI	Short for lines per inch; refers to the frequency of horizontal and vertical lines on a halftone screen.
luminence	Refers to the black-and-white information, including brightness, sharpness, and contrast, encoded in a video signal or graphic image.

macro	The ability of a lens to focus at very close range.
map	The process of making one image conform to the size, shape, and/or texture of another.
mask	A defined area used to limit the effect of the image-editing operations to certain regions of an image; masks can be drawn manually with a stylus or a mouse, or they can be created automatically.
megapixel	A measurement of 1,048,576 pixels (approximately 1 million pixels).
Memory Stick	Sony Electronics-based storage media used predominantly in Sony's cameras, computers, and MP3 players.
moire pattern	An unwanted effect that appears in digital scans of images.
monochrome	A term used to refer to a bi-level graphic; also refers to a single-channel grayscale image.
morphing	A special visual effect, used in both film and video, which produces a smooth transformation from one object to another.

ND filter	Short for neutral density filter; used to reduce the amount of light passing through a lens without altering the image's colour or tonal rendition.
negative	This is a piece of processed film in which the image is reversed so that the shadows are light and the highlights are dark.
neutral colour	In RGB colour mode, equal amounts of red, green, and blue make a neutral colour.
noise	Refers to sound, signal, or data that was not originally intended to be included.
nonrecoverable error	This is an uncorrectable change in colour from that of the original image.
normal lens	A lens that accommodates an image of approximately the same angle of view and the same proportion as that of which the human eye is capable.

opacity	The amount of transparency when combining a fill colour, painted colour, floating selection, pattern, or layer with another layer or background.
optical filtering	Refers to the process of selectively transmitting or blocking a range of wavelengths of light.
optical sampling rate	The number of samples that are captured by a scanner per linear distance as determined by the optics, electronics, and mechanics of the system.
overlay proof	A proof created from colour separation negatives that uses sheets of acetate overlaid on each other to create the colour image. Each film layer represents one colour.

palette	A computer graphics term describing the collection of colours or shades available to a graphics system or program.
pan	A camera technique in which the point of view is adjusted by moving the camera direction along the horizontal plane.
pattern recognition	Computer-based recognition of forms or shapes within an image.
PXC	A PC file format used for graphics.
phosphors	Tiny red, green, and blue grains on the inside surface of a CRT monitor that are illuminated when an electron beam is directed toward them.
PhotoCD	A popular storage method for digital images developed by Kodak.
photometer	Also called a light meter, this is an instrument used to measure luminous intensity, luminous flux, illumination, or intensity of light.
PICT	A Macintosh file format used for graphics.
pixel	Short for picture element; a pixel is a single point in a graphic image.
pixel dropping	A subsampling technique used to reduce the number of pixels in an image by dropping every nth pixel from the scan.
pixelisation	The graininess in an image that results when the pixels are too big, relative to the size of the image.
PMS	Short for Pantone Matching System; a trademarked standard for specifying and producing spot colors using proprietary ink mixes.
polarisation	This is the use of specific filters to control the direction light travels. Effects include the reduction of glare and reflections and the saturation of colours, especially in landscapes.
polarising filter	These are two pieces of polarising material that rotate on a common axis so that the polarising effect can be increased or decreased on the camera lens.
positive	Also referred to as a slide or transparency; this is a photographic image in which the light areas correspond to light areas in the subject, and the dark areas correspond to the shadow areas in the subject.
posterisation	The effect produced when a photographic image is displayed or printed with a small number of colors or shades of grey.
PPI	Pixels per inch; the measurement of resolution for display or print elements.
primary colours	Three colours (red, yellow, and blue), which when combined at various proportions can produce every other colour.
purple fringing	Chromatic aberration at microlens level.

quadtone	A printed image created with four different colours of ink.
QSIF	Short for Quartersize Image Format; an image format in which the image is reduced to 176 by 112 pixels.

radial fill	A fill projected outward in all directions from a central point.
raster	A pattern of scanning for input or output, which provides uniform coverage of a two-dimensional surface, such as a monitor screen, a scanner bed, or the CCD array in a digital camera.
rasterisation	The process of converting a graphic image to a bitmap.
rangefinder	Device in some cameras used to measure the distance from the camera to the subject and that indicates when the subject is in focus.
redeye	A photographic phenomenon caused by light reflecting off the interior surface of the eye, which produces a red glare within the eye.
reflectance	Also called reflectivity, this is the fraction of the light incident on a surface that is reflected. Reflectance varies according to the wavelength distribution of the light.
relative aperture	Also known as the f-stop, this is the diameter of the aperture of a camera divided by the focal length of the lens.
resample	To change the resolution of an image.
resolution	A measure of the proportion of the smallest individually accessible portion of a video image to the overall size of the image. The higher the resolution, the finer the detail that can be discerned.
RGB	Short for red, green, blue; the colour model used for generating video on a display screen. It displays colours as varying intensities of red, green, and blue dots.

sampling rate	The number of samples obtained in a digitiSation process per unit of time or distance.
saturation	Also known as colour purity or the amount of colour density, the degree to which a colour is diluted by luminance, or white light.
scale	To enlarge or reduce an image by increasing or decreasing the number of scanned pixels.
scanner	An electronic input device that captures a digital image or objects into a computer.
SCSI	Short for small computer system interface; a defined standard for the connection of mass storage and other input/output devices to a computer. A scanner or printer may employ a SCSI interface in order to communicate with a computer.
separations	Monochrome negatives that separate the continuous colours of an image into two to four colours for offset printing.
shadow detail	These are subtle features in the darker part of an image.
sharpen	A computer graphics process that enhances the contrast on the edges of light and dark shapes to make images appear more in focus.
sharpness	A reference to whether an image appears to be in focus.
shutter	Mechanism that opens and closes at specified intervals in order to allow light to pass through the lens.
SIF	Short for Source Image Format; refers to the original image format on which the source image was taken.
signal-to-noise ratio	The ratio of the usable signal to unusable noise in any signal. In imaging, this represents the quality of the scan.
slide scanner	The ratio of the usable signal to unusable noise in any signal. In imaging, this represents the quality of the scan.
slide scanner	The ratio of the usable signal to unusable noise in any signal. In imaging, this represents the quality of the scan.
smoothing	Also known as antialiasing, this is the electronic process of eliminating or reducing jaggies in an image.
spectral sensitivity	The relationship between the radiant sensitivity and the wavelength of incident light.
speed	A rating that determines the light sensitivity of the film; ASA (American Standards Association) and ISO (International Standards Organization) provide a standard measure by which all photographic film speeds are determined. However, all digital cameras rate their CCD's sensitivity as equal to that of a given ISO standard.
SPIFF	Short for Still Picture Interchange File Format; proposed by the ISO as a standard file format for the transfer of still images.
stopping down	In photography, this is the process used to decrease the size of aperture in a lens.
subtractive primary colours	Ink or other colourants, such as paint, that when combined together in equivalent amounts produce absolute black, or, when combined in different ratios, produce any colour other than black.
SVGA	Short for Super Video Graphics Array; defined by IBM; represents a computer graphics adapter capable of 800 by 600 resolution.
system palette	A colour palette chosen by a computer system and applied to all digital images.

TGA	Short for True Vision Targa File; a storage format for bitmapped video images.
thumbnail	A small representation of an image; used as an aid in indexing, previewing, or cataloging graphics images.
TIFF	Short for Tagged Image File Format; a computer graphics file format developed by Aldus, Adobe, and Apple.
transmittance	The fraction of the incident light that passes through an object.
tritone	A printed image created with three different colours of ink.
truecolour	A term used to describe an image that has a bit depth similar to the response of the human eye and which is considered to represent colour as seen through the human eye.
TWAIN	A programming interface that lets a graphics application, such as an image-editing program or a digital camera, activate a scanner, a frame grabber, or another image-capturing device.

UCR	Short for undercolour removal; reducing the cyan, magenta, and yellow inks from the darkest neutral shadow areas in an image by replacing them with black ink.

value	The relative lightness and darkness of a colour or tone.
VGA	Short for Video Graphics Array; defined by IBM; represents a computer-graphics adapter capable of 640 by 480 resolution. Also see SVGA.
video digitiser	Also called a frame-grabber, this is an image capture device that employs a video camera attached to a circuit board in a computer, which converts the video signal into a digital file.
viewfinder	An optical or electronic display used to frame an image in the camera. One looks through the viewfinder in order to see the image that will be captured by the camera.
vignetting	The action of blurring the background so that the subject stands out.
visible light	The portion of the electromagnetic spectrum that the human eye can see, bordered on the "red" end by infrared, and on the "blue" end by ultraviolet.
VRAM	Short for video random access memory; a special high-speed type of RAM that is used temporarily to store visual information being transferred to the display hardware in a computer.

watermark	These are bits altered within an image to create a pattern that indicates proof of ownership. Unauthorised use of a watermarked image can be traced.
white balance	This is the balancing of colour components to create pure white when scanning a white object.
wide-angle lens	A lens that has an angle of view greater than that of a standard lens and that is considered of short focal length. This kind of lens is usually employed to include more of a subject within the confines of the image frame.
WYSIWYG	Short for what you see is what you get, this term refers to the graphical interface that allows you to see onscreen what you will be able to print.

zoom lens	Lens with variable focal length within a certain range.

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