This glossary contains Photographic and Digital Imaging term.

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 #

- A-

A3
Paper size for documents measuring up to 11.7" x 17".

A4
Paper size for documents measuring up to 8.27" x 11.69".

A5
Paper size for documents measuring up to 5.83" x 8.28".

A/D converter
A device used to convert analog data to digital data. Analog data is continuously variable, while digital data contains discrete steps.

Aberration
(1) Something that prevents light from being brought into sharp focus, disenabling the formation of a clear image.
(2) Lens flaw - the inability of a lens to reproduce an accurate, focused, sharp image. Aberration in simple lenses is sub-categorized into seven types:

• Astigmatism - lines in some directions are focused less sharply than lines in other directions,
• Chromatic aberration or Axial chromatic aberration - different wavelengths of light coming into focus in front of and behind the film plane, resulting in points of light exhibiting a rainbow-like halo and reduction in sharpness,
• Coma - the image of a point source of light cannot be brought into focus, but has instead a comet shape,
• Curvilinear distortion - distortion consisting of curved lines,
• Field curvature - the image is incorrectly curved,
• Lateral chromatic aberration also known as Transverse chromatic aberration - variation in the magnification at the sides of a lens (this aberration type used to be termed “lateral colour”),
• Spherical aberration - variation in focal length of a lens from center to edge due to its spherical shape - generally all parts of the image, including its center.
  The effects of lens aberration usually increase with increases in aperture or in angle of field.

- B -

B (bulb)
Is the letter on the shutter dial that the shutter will stay open while the real is depressed. This is used for time exposure that are longer than your camera's preset shutter speed.

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

Background
Areas shown behind the main subject in a picture.

Background colour
This is the colour that appears when part of an image is erased, cut or deleted

Background Processing
Allows assignment of specific operations to the background while the computer continues to perform previously assigned instructions.

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-lighting
Light coming from behind the subject.

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 ).

Balanced fill-flash
Balanced fill-flash is required. 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.

Banding
A visible stepping of shades in a gradient. A artifact of colour gradation in computer imaging, when graduated colours break into larger blocks of a single colour, reducing the smooth look of a proper gradation.

Bandwidth
General term for the amount of data that can pass through a given channel at one time. When using a dialup connection, the Internet for example, your bandwidth is limited by your telephone connection and modem, and will typically be 2-4 kilobytes per second. Information requiring more than this flow of data will be impractical for this connection.

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 center 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 and estar.

Base exposure time
Is the initial exposure time used for making a "straight" print.

Base plus 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 resolution
The PhotoCD image resolution (512 x 1024) that is established for display on current televisions.

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.

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

Batch processing
The performing of a group of computer tasks at the same time.

Batch scanning
Sequential scanning of multiple originals using previously-defined, unique settings for each.

Batteries
Batteries for digital cameras can range from AA size to NiCad (nickel-cadmium), to NiMH (nickel-metal hydride) to lithium ion.

     nickel cadmium (NiCad): Rechargeable batteries that use an alkaline electrolyte. They have a longer life than non-rechargeable batteries.     
     NiCad batteries have a memory, so they need to be run all the way down before recharging. Otherwise, they will begin to run out of power sooner.

     nickel metal hydride (NiMH): A rechargeable battery that lasts longer than a NiCad and has no memory, so it is easier to manage.

     lithium ion: More expensive than either the NiCad or NiMH, but holds a charge much longer.

Baud
Named after the French telecommunications technician Baudot. It is the unit used to measure data transfer (1 Baud = 1 bit/sec.). Therefore, for example, the specification - "28,800 Bauds" means that data can be transferred at a rate of 28,800 bits per second.

Bayer pattern
A pattern of red, green, and blue filters on the image sensor's photosites. There are twice as many green filters as the other colours because the human eye is more sensitive to green and therefore green colour accuracy is more important.

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
An accordion-like, light tight device. On a camera, it goes between the lens and the camera body. When used as an accessory to a 35mm camera, it enables it to focus on a close subject and achieve a greater-than life-size magnification on film. On an enlarger, it goes between the lens and the enlarger head and the lens is focused by adjusting the length of the bellows.

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. Most medium format cameras like the Hasselblad have one family of lens with shuttle and another without. Most lenses in this family have a smaller maximum aperture than the other family.

Bézier curve
A mathematical curve that describes a vector path. In Photoshop Bézier curves are created by plotting anchor points with the pen tool.

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

Big data
Any part of a layer that extends outside the physical dimensions of a Photoshop document.

Bilevel
A type of image containing only black and white pixels.

Binary number system
A numbering system used in computers consisting of only 1's and 0's.

Bios
Basic input / output system. The computer part that manages communications between the computer and peripherals.

Bit
The basic unit in a binary numbering system. Binary Digit.

• A single bit is expressed in the base 2, either on or off.
• Imagine using bits of data to express gray scale. Progressive levels display are expressed as increasing powers of 2.
• In a one bit system (21) there would only be white or black.
• A four bit system is 24 (16 gray scale levels) where a six bit system is 26 (64 levels of gray). The more gray, the better the picture.

Bit depth
This refers to the grey scale range of an individual pixel. A pixel with 8 bits per colour gives a 24 bit image (8 bits X 3 colours is 24 bits). CCD sensors are coloured in a pixel by pixel method.

30/32 bit colour is billions of colours

24 bit colour resolution is 16.7 million colours.

16 bit colour is 65,536 colours

8 bit colour is 256 colours

8 bit grey scale is 256 shades of grey

1 bit is black or white.

Bitmap
The method of storing information that maps an image pixel, bit by bit. There are many bitmapped file formats, .bmp, .pcx, .pict, .pict-2, tiff, .tiff, .gif (89a), and so on. Most image files are bit mapped. This type of file gives you the jaggies, when examined closely you can see the line of pixels that create edges. Bitmap images are used by all computers. The desktop or screen information for all Windows machines uses .bmp files, while the Macintosh uses pict files

Bit mapped image
An image created from a series of bits and bytes that form pixels. Each pixel can vary in colour or gray-scale value. Also known as a raster image.

Bitonal
An image or file comprised of pixel or dot values of either black or white.

Black
In four-colour printing (CMYK) black is the fourth colour, represented by the " K ".

Black generation
When converting an RGB image to CMYK colour mode, black generation refers to the values that are generated for the black plate used in commercial printing.

Black limit
A colour separation setting that establishes the maximum percentage of black ink in a CMYK image. The setting is made before an RGB image is converted to a CMYK image. The press and paper planned for the publication usually determine the proper black limit setting.

Black point
This is the colour that produces colour values of 0, 0, 0 for each of the RGB components when scanned or digitized. Normally, the black point is 0 percent neutral reflectance or transmittance.

Black point compensation
A setting in Photoshop that adjusts for differences in black points when converting colours. When selected, the full dynamic range of the source colour space is mapped to the full dynamic range of the destination colour space. When deselected, the dynamic range of the source colour space is simulated in the destination colour space.

Bleach
A chemical bath to convert the black metallic silver that forms a photographic image into a compound such as a silver halide, which can then be dissolved or dyed. Bleach is used in toning and in many colour processes.

Bleed
Printing term referring to an image or inked area which extends to the edge of a printed piece. The bleed is the portion of the artwork that is beyond the trim marks of the piece. The bleed is required to account for any slight misalignment during trimming which would otherwise result in an unprinted strip of paper appearing at the edge of the finished piece.

Blemishes 
Pimples, scars, spots, and other defects which may be softened or removed by negative retouching, print spotting, and/or airbrushing (sometimes called "artifacts").

Blend
In computer graphics software, the intermediate steps between two objects that are created when the objects are merged together via a specified number of intermediate transformations.

Blooming
Each pixel (photosite) on a digital camera sensor (CCD/CMOS) has a limit as to how much charge it can store. Blooming (or Streaking) is the name given to an overflow of charge from an over saturated pixel (photosite) to the next on the sensor. This problem is addressed with the addition of "anti-blooming gates" which can be thought of as vertical drain ditches running beside each row of pixels, these gates allow the overflowing charge to run away without affecting surrounding pixels. Anti-blooming gates, while mostly successful (and certainly for more modern sensors) blooming can still be a problem in very extreme exposures (very bright edge against a virtually black edge) and is typically visible as either a vertical streak or white halo extending for several pixels. The effects of blooming often amplify the visibility of chromatic aberrations. Blooming is really good at destroying the detail of leaves shot against a bright sky.

Blotters
Sheets of absorbent paper made expressly for photographic use. Wet prints dry when placed between blotters.

Blowup
Slang for 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.

Bmp
File format extension for bitmap images.

Body
The light-tight box that contains the camera mechanisms and protects the film from light until you are ready to make an exposure.

Bordering
Automatically locating the correct edge of an image on a scan so that marking from the edge, frame, etc is not capture.

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 center 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.

Boot
To start or restart your computer; loading your operating system.

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. Sometimes also called  " Bounce lighting." 

Bounce light
Light that does not travel directly from its source (bounce flash) to the subject but is first reflected off another surface. This technique softens the light by directing it at a ceiling, wall, board, or similar surface before it reaches the subject.

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 hyperfocal 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.

Bpi (Bits per Inch)
Defines the density of data in a bitmap image.

Bps ( bits per second )
Refers to the number of bits transferred in one second. The bps not often found on modems and serial interfaces.

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.

Bracketing
To make several exposures, some greater and some less than the exposure that is calculated to be corrected. Bracketing allows for error and permits selection of the best exposure after development.

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.

Broad Lighting
Conventional portraiture often positions the model in a pose such that their bodies are not facing the camera directly, but are turned to one side or the other. If the main light is positioned such that the illuminated portion of the face is framed in the image rather than the shadowed portion as in Short Lighting.

Browser
A program used to display information, especially on the Internet.

Buffer
A special area set aside either in hardware or software for temporary storage. Usually, the bigger the buffer, the faster the computer can process other data.

Buffer ram
Fast memory chip in a digital camera. Buffer Ram is used to store images whilst they are recorded onto the much slower removable media card. This allows cameras to take a number of shots in rapid succession without waiting for the previous image(s) to be written to the card.

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 setting
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
Basically, a darkroom process that gives 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.

Burst images
A series of images taken in rapid succession, captured at a preset speed. Burst images are usually used to capture a person or object in motion. The number of images captured will vary, depending on how long the shutter button is held down and how much memory is available.

Bus
A path in the computer to transfer information within the computer or to the device(s) to which the data are addressed.

B&W
Abbreviation that stands for " black and white. "

Byte
A unit of measure equal to 8 bits of digital information. The standard measurement unit of a file size. See also Kilobytes, Megabyte and Gigabyte.

                             1000 Bytes of computer information               =     1 Kilobyte
                             Kilobytes represents a million characters of information. 
                             1,000,000 Bytes of computer information       =     1 megabyte
                             Megabytes represents a million characters of information.
                             Actually one megabyte  =  1,048,576 bytes.
                             100,000,000 Bytes of computer information   =      1 Gigabyte
                             Gigabytes represents a 100 million characters of information.

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- C -

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.

Cache
A temporary storage area for information which locates itself between the hard disk and the RAM by employing intuitive logic. It also speeds up access time of the data.

Calibration
The act of adjusting the colour of one device relative to another, such as a monitor to a printer, or a scanner to a film recorder. Or, it may be the process of adjusting the colour of one device to some established standard.

Calibration bars
An 11-step grayscale in 10% increments from 0% to 100% that prints along the edge of a page. When outputting colour separations a progressive colour bar is also printed. Calibration bars can be read with a densitometer to insure accurate output and printing.

Camera angles
Various positions of the camera with respect to the subject being photographed, each giving a different viewpoint and perspective.

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.

Camera shake
Movement of camera caused by unsteady hold or support, vibration, etc., leading, particularly at slower shutter speeds, to a blurred image on the film. It is a major cause of un-sharp pictures, especially with long focus lenses.

Candle meter
Also known as a 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.

Capacity
The amount of information, measured in bytes, that can be stored on a hard drive. Also known as storage capacity.

Caption
Text that provided detailed information about the image such as, who, what, where, why, when and where. Photo credit, source, date, caption editor and other IPTC information

Capture
Acquiring an image by a scanner or digital camera.

Card reader
An Electronic device, which is connected to your computer to transfer pictures from memory cards from digital cameras to your computer.

Carriage
Part of a flatbed scanner that travels the length of the scanner bed. The illuminating lamp is mounted on the carriage to provide light for the image. In a CCD scanner, the carriage has mirrors mounted on it which reflect the image back to the CCD. In a CIS scanner, the carriage contains the CIS elements. Also Known as a scanhead.

Catchlight
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.

Cathode ray tube ( CRT )
Standard monitors for computers are CRTs. CRTs use the colours of red, green, and blue for display.

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.

CCD
Charged Coupled Device, a light sensitive chip used for image gathering. In their normal condition these are grayscale devices. To create a colour pattern is laid down on the sensor pixels, using RGBG colour mask. (Red, Green, Blue, and Green) The extra Green is used to create contrast in the image. The CCD Pixels gather the colour from the light and pass it to the shift register for storage. * CCD are analog sensors, the digitizing happens when the electrons are passed through the A to D converter. The A to D converter converts the analog signal to a digital file or signal.

Area CCD:A square or rectangular CCD that can capture an entire image at once, which is essential for dynamic subjects and flash photography.

Linear CCD: Scanner-type CCD, these sensors are long and thin, and capture an image by recording a vast number of individual "exposures" while scanning across the picture frame. These are best suited for still subjects and continuous illumination.

CD
Compact Disc- A read only storage media typically capable of holding up to 650 MB of data.

CD burning
Saving your digital file to a CD. Usually, after we scan an image, we burn it to CD and send it to you.

CD-R
Compact Disc Recordable writes data to discs, which can then be read by standard CD-ROM drives.

CD-ROM
Compact Disc-read Only Memory. A CD-ROM drives uses the CD (compact disc) format as a computer storage medium. One CD can store 640 megabytes of data and other mixed media on a disc about the size of a traditional 5-1/4 in. floppy disk.

Centering
Positioning a image properly within the digital field of vision so that it is framed appropriately.

Center 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 center weighted metering, most of those spots will be in the center area of the picture. (See Bottom weighted and exposure.)

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.

Channel
Photoshop uses the term Channels to describes black and white and colour image data. In Photoshop, one channel id typically defined as having up to eight bits of grayscale image information. Continuous tone images created with a scanner use channels as a way to describe the black and white and colour image data. A black and white grayscale image has one channel. An RGB colour image has three channels. A CMYK colour image has four channels. It is possible to have up to 24 channels in photoshop.

Characterization
The process of creating an ICC profile that describes the unique colour characteristics of a particular device such as a monitor, scanner, colour printer, and printing press. Press profiles may be based on standards such as SWOP. Resultant ICC profiles define the gamut of a device in the context of a device-independent colour space so that colours may be mapped to or from the device gamut.

Characteristic curve
A graphic representation of the relationship of the film's exposure to light and the density of the resulting image. Also called the D log E curve, since density is plotted against the logarithm of the exposure.

Chroma
The quality of a colour that is the combination of hue and brightness. In the Munsell system of colour notation, chroma indicates the purity of a colour as measured along an axis; the farther from the axis, the purer the colour.

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 photographic process by which a print is made directly from a colour transparency. It is noted for rich colour, brilliant clarity, and outstanding archival-quality for colour prints. Also called Ilfochrome.

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.

Circle of confusion
Any sufficiently small circle is indistinguishable to the human eye from a point. As long as a lens resolves a point as a circle that is small enough, its resolution is adequate: though a lot depends on how much the image is to be enlarged, and the lighting conditions under which it is to be displayed, to say nothing of variations in individual eyesight. The size of the circle of confusion is a matter of dispute, especially with classic large format lenses.

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.

Clip art
Graphic files that are usually distributed on CD-ROMS and can be inserted into documents, presentations, and projects.

Clipping
The removal of some portion of an input signal or quantity from the resulting output, generally by setting certain low and high thresholds and discarding the data that falls below the low threshold or above the high.

Clock Speed
The speed of the computer is measured by electronic circuits in an internal timing device.

Cloning
To make an exact duplicate of digital image data. In digital systems it is possible to copy part of an image onto another.

Clut ( Colour Look-Up Table )
A colour indexing system used by some computers to reference colour if their systems do not support a high bit depth to represent all colours.

Close-up
A general term for an image of a close subject, i.e. filling the frame.

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.

CMOS
(Complementary Metal Oxide Semiconductor) A sensor similar to CCD. CMOS semiconductors use two circuits, negative and positive polarity circuits. Because only one of the circuits can be on at once, CMOS chips are less energy consuming than other chips that utilize simply one type of transistor. This is a clear advantage of the CMOS sensor over the standard CCDs in use today.

CMS
"Colour management system" This ensures colour uniformity across input and output devices so that final printed results match the original.

CMY
Cyan, Magenta, Yellow. The three subtractive colour primaries.

CMYK
Cyan, Magenta, Yellow, Black; These are the printer colours used to create colour prints. Most Colour Printers, Ink-Jet, Laser, Dye-Sublimation, Thermal, and Crayon printers use these as their printer colours. (This is one of the colour management problems for computers. Converting RGB files to CMYK files causes colour shifts.) When used by a printer the CMYK is also known as a reflective colour since it is printed on paper, or reflective films

Coated lens
A lens with air-glass surfaces which have been coated with magnesium fluoride to reduce lens flare. 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.

Colorant
A dye, ink, pigment, wax, or other material used to impart colour.

Colorimeter
A precision instrument used to accurately measure tristimulus value of a colour in the way the human response system sees colours. Typically colorimeters are used to measure the Red, Green and Blue components of a light source, such as a colour monitor.

Colour balance
( 1 ) The overall hue of the colour in a colour reproduction. Correct colour balance implies that the colours in the scene are reproduced satisfactorily for the desired effect or realistic duplication.
( 2 ) Referring to colour films, they are balanced in manufacture for exposure to light of a certain colour quality ; i.e., daylight, tungsten, ect.

Colour banding
The appearance of visible bands of colours that replace subtle gradations in order to accommodate a reduced palette.

Colour calibration
The process of ensuring accurate reproduction of colour for images. Full colour calibration is usually a two-step process: calibrating your input device, such as a scanner; and calibrating your output device, such as a printer or monitor. By calibrating input and output devices correctly, colour is accurately captured by your scanner and is reproduced faithfully on your monitor or printer as well.

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. Also caused, when scanning, by the sometimes unpredictable interaction between an image and a scanner.

Colour channel
Refers to the Red, Green and Blue components from which colours are created.

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 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 value
A mathematically calculated value of a pixel's colour based on its colour components.

Colour value
A mathematically calculated value of a pixel's colour based on its colour components.

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.

Colour quantization
The process of finding the best set of colours (palette) for representing an image. Two common methods are "median cut," which works best for real-world (scanned or photographed) images, and "popularity," which does well for drawn images. The popularity method simply picks the n colours used the most in the image. This tends to omit colours for highlights in photographs, which are important, although not the most popular. The median cut method assigns all available colours to groupings, then splits the groupings to determine a representative set of colours. The more bits available for each colour component, the more memory and time required to quantize, and the better colour matches that are obtained.

Colour wheel
The visible spectrum's continuum of colours arranged into a circle, where complementary colours such as red and green are located directly across from each other.

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.

CompactFlash
Flash memory card measuring 1.5 inches square, developed by Scandisk; used in small portable devices such as digital cameras, MP3 players and PDA's and available in a variety of multi-megabyte capacities. The controller is built onto these cards, so as new and faster controllers are designed you can purchase the newer card and take advantage of faster write time. These tend to be a bit more expensive than Smartmedia ( SSFDC ) cards. Any device that is designed to use a CF card can use any brand of CF cards so long as it meets the CFA ( Compact Flash Association ) standards ( virtually all of them do ). These are palmtop computers, voice recorders, and other devices that can use the same cards as your CF compatible camera.

Compatibility
The ability for data, programs (software) and equipment (hardware) to run and/or work together. This allows for the individual components to be put together to form a system.

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 arrangement of the elements within a photograph--the main subject, the foreground and background, and supporting objects.

Compressed A compressed image is one whose file size has been reduced. Some compression schemes maintain the quality of the image (lossless) and some do not (lossy or destructive). See also Compression

Compression
The process of reducing the size of a digital file, usually through software. This speeds processing, transmission time and reduces storage requirements.

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 that uses specular light and has several lenses (condensers) to concentrate the light and increase the illumination. It produces images with more contrast and sharper detail than a diffusion enlarger.

Configuration
The choices you make when setting up a computer system to meet your needs.

Connectivity
A digital camera's connectivity defines how it can be connected to other devices (computers primarily) for either the transfer of images or remote control of the camera. Image Transfer - Early digital cameras used RS232 (serial) connections for image transfers. Most consumer grade digital cameras now feature USB connectivity, this provides a relatively fast transfer rate (up to 500 Kbyte/s) to a wide range of computer systems on the PC and Mac platforms. Manufacturers generally bundle such cameras with cables and driver software. One step up from USB is FireWire (IEEE1394) seen mostly on professional digital cameras, this offers considerably faster transfer rates but requires that your computer has a FireWire connector or you're willing to fit it out with FireWire.

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
Is an apparatus used for making contact prints. Equipment ranges from a contact printing frame to more sophisticated boxes with safe lighting.

Contact sheet ( Contact proof )
A gang sheet made by placing film directly in contact with the photographic paper. All images appear on one sheet of paper in the same size as the film.

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

Continuous shutter
A feature found on more expensive digital cameras that enables you to take several images in quick succession; the images are saved to the memory card after the multiple exposures have been taken.

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.

Continuous tone ( CT ) device
A device that renders images by using tone values of different densities without applying halftone dots.

Continuous burst or capture mode
The ability to take multiple pictures in a small amount of time. Great for action shots.

Continuous shooting
Camera feature that allows a camera to take several rapid-fire exposures when the shutter button is held down. This feature is useful for shots where there is quick action and you want to take multiple shots.

Continuous-tone image
An image containing gradient tones from black to white.

Contouring
Another name for banding or posterization.

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
Describes a scene, negative, or print with very great differences in brightness light and dark areas. Opposite: flat.

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 .

Conversion
In computer imaging, to change a CMYK file to RGB or vice versa, or to convert one file format to another.

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

Cool colours
Blue, purple, and brown.

Copystand scanner
An image-capture device that sits on a copystand and can be raised or lowered to get closer to or farther away from the material to be scanned.

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.

Correlated noise
A recognizable pattern of change in an image file, based on an increase or a decrease in the brightness of the pixels compared to what they should be. Vertical patterns of correlated noise are often called streak noise and are common problems with CCD technology. Also called periodic noise.

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.

CPU
Central Processing Unit: A large chip which holds the " brain " of the computer.

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.

Crossed polarization
A system of using two polarizing filters, one over the light source and one between the subject and the lens. With certain materials crossed polarization causes bi-refringent effects which are exhibited as coloured bands. Used in investigations of stress areas in engineering and architectural models.

CTP
Computer-to-plate, a technology for converting digital page layout files directly to press-ready printing plates, without an intermediate film satge.

Cursor
A location marker or pointer on the monitor.

Curvature of field
Where light rays passing through a lens causing the lens to focus on a curved plane versus a flat plane. This causes out-of-focus pictures.

Custom colour printing
The art of producing, from one's knowledge of colour, a print that looks better and is more pleasing than a print that can be made purely by machine or colour management system.

Cut / paste
To cut out an image or line element, usually by masking it, and repositioning the elements (s) elsewhere.

Cyan
One of the three subtractive primary colours. It is produced by mixing equal amounts of blue and green and is the " C " in CMYK

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- D -

D50
The CIE Standard Illuminant that represents a colour temperature of 5000 K. This is the colour temperature that is most widely used in graphic arts industry viewing booths.

D65
The CIE Standard Illuminant that represents a colour temperature of 6504 K.

Darkcloth
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 room or small area that can be made completely lightproof, so it can be used for working with photographic film, paper, or other light-sensitive materials.

Data
The number that make up a digital file.

Database
A database is a collection of data that is organized so that its contents can easily be accessed, managed, and updated.

Data compression
Digital cameras don't have the massive amounts of storage a computer does, yet they create files that can be quite large. Because of this, the camera compresses used, the better the image. The more compression used, the more images can be stored.

Daylight Balance
Most film available on the market today is Daylight Balanced. Unless the film specifically states that it is balanced for other lighting conditions, it will probably be designed for daylight. This film will produce natural colors when exposed under natural (outdoors) conditions or under normal flash. When shot under tungsten lighting (incandescent light bulbs) there will be a reddish yellow tint to the photo and when shot under fluorescent lighting there will be a green hue.

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

Dedicated flash
Electronic flash that must be used with specific cameras to automatically adjust the camera's exposure controls to produce the correct exposure.

Decompression
When a image or other digital data set is compressed and stored, it is not usable until it is decompressed into it's original form.

Default
The setting in a computer program which will take effect if no change are made.

Definition
Sharpness of an image ( as seen by the clarity of detail ) formed by an optical system.

Defringe
Blends the pixels along the edge of a selection to seamlessly merge it with a new background.

Degauss
Process of eliminating magnetism, such as with a colour monitor face plate, to eliminate distortion.

Delayed action
Mechanism delaying the opening of the shutter for some seconds after the release has been operated. Also known as self-timer.

Delta-E
The distance between two colours in the CIELAB colour space, used to indicate colour differences and to establish quantitative colour tolerances.

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 electronic device for measuring the amount of light transmitted through or reflected from a sample, such as the gray percentage values in halftone films.

Density
The relative amount of silver in various areas of film or paper after exposure or development therefore the darkness of a photographic print or the light-stopping ability of a negative or transparency.

Depth of field
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. You can control or exploit depth of field 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 you decrease the size of the aperture, the depth of field increases; If you focus on a distant subject, depth of field will be greater than if you focus on a near subject; and if you fit a wide-angle lens to the camera, it will give you 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
Depth of focus refers to the zone in front of and behind the focal plane in which the blurred image point is smaller than the acceptable circle of confusion. An image, if it is not on the focal plane but within the depth of focus, is distinguished as a sharp image although it is, in fact, slightly blurred. Depth of focus depends on the f-number and the acceptable circle of confusion. The focal length of the lens does not affect the depth of focus.

Derived Image (Derivative Image)
An image that has been created from another image through some kind of automated process, usually involving a loss of information. Techniques used to create derived images include sampling to a lower resolution, using lossy compression techniques, or altering an image using image processing techniques.

Descreening
Removal of halftone dot patterns during or after scanning printed matter by defocusing the image. This avoid moiré patterning and colour shifts during subsequent halftone reprinting.

De-skewing
Straightening an image that as been scanned crookedly, or straightening type that is slanted.

De-speckle
To remove or reduce speckles or dust spots introduced during scanning or image processing.

Detent
a click stop in the shutter release button, a place where the mechanism is designed to register specific information such as exposure or focus before the button is fully depressed.

Developer
A solution containing a number of chemicals that will convert a latent image on a exposed photographic material to a visible image.

Developing tank
A light-tight container, made of plastic or steel, in which film is developed. The exposed film is loaded into the tank in complete darkness, and temperature controlled chemicals are added at precisely timed intervals to make the image and stable.

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.

Device driver
Software that tells the computer how to communicate with a peripheral device, i.e. printer, CD-ROM.

Device-dependent
Describes a colour space that can be defined only by using information on the colour-rendering capabilities of a specific device.

Device-independent
Describes a colour space that can be defined using the full gamut of human vision, as defined by a standard observer, independent of the colour- rendering capabilities of any specific device.

Device profile
A representation, in the CIE model, of the colour rendering characteristics of any input, display or output device.

Diaphragm
The part of the camera that governs the size of the aperture. The most common type is the iris diaphragm- a system of curved, overlapping metal blades that form a roughly circular opening similar to the iris of the eye. It varies in size to control the amount of light.

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.

Diffusion disk
A flat glass with a pattern of lines or concentric rings that breaks up and scatters light from an enlarger or camera lens and softens detail in a photograph.

Diffusion enlarger
An enlarger that illuminates the negative by scattering light from many angles evenly over the surface of 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.

Digital
A system whereby information is represented by binary digits, or "bits." Binary information has two states, "0" and "1,"or "on" and "off," and can thus be easily processed by electronic systems. Analog information can be converted to and from digital information via devices called "Analog to Digital Converters" or "Digital to Analog Converters." Digital information does not suffer from the degradation and noise problems prevalent in analog circuits.

Digital camera
Instead of using film, this kind of camera records data in "pixels," small squares of light of varying hues that can be directly loaded into and interpreted by a computer.

Digital Duplicates
Reproductions of an image that are produced by scanning the original analog image to produce a digital image file, and then imaging the digital file using some variety of digital printing or recording device.

Digital envelope
A digital "container" that surrounds an image with information (or metadata) in a file. Such information might be used to find the image, guarantee its authenticity, or limit access to authorized users. An envelope adds additional "overhead" to a file in excess of the actual "data" of an image.

Digital film
The analogous component in digital cameras to film in optical cameras. This usually consists of some type of semiconductor memory, with or without additional components, usually in the physical form of a removable cartridge.

Digital Halftone
The use of fine pixels to create the halftone pattern that is then written to film, direct-to-plate or direct-to-press for printing.

Digital- image filtering
Processing on an image performed by combining or comparing individual pixels with their neighbors. Many interesting and useful effects can be obtained, such as sharpening, blurring, edge detection, and embossing.

Digital imaging
A method of image editing in which a picture is recorded as digital information that can be read and manipulated by a computer, and subsequently reformed as a visible image.

Digital internegatives
Internegs that are produced by digitally scanning the original transparency to create a digital file, and then imaging the digital data using a film recorder to record the image onto a negative film stock.

Digital printer
A printing device that is capable of translating digital data into hardcopy output.

Digital Signal Processors (DSP)
Microprocessor chips specially designed to convert, modify and manipulate streams of digitized signals in real time. These chips allow for faster telephony, faxing, and audio and video capture and editing.

Digital Zoom
Rather different from Optical Zoom.  With Digital Zoom the image is magnified by spacing out the pixels electronically, and as such is really very little different from blowing an image up to a larger size using a software package on your PC.  Digital Zoom has a detrimental effect on image quality, so depending on your application, you need to be careful how you use it.  

Digital imaging
A method of image editing in which a picture is recorded as digital information that can be read and manipulated by a computer, and subsequently reformed as a visible image.

Digital internegatives
Internegs that are produced by digitally scanning the original transparency to create a digital file, and then imaging the digital data using a film recorder to record the image onto a negative film stock.

Digital printer
A printing device that is capable of translating digital data into hardcopy output.

Digital Signal Processors (DSP)
Microprocessor chips specially designed to convert, modify and manipulate streams of digitized signals in real time. These chips allow for faster telephony, faxing, and audio and video capture and editing.

Digital Zoom
Rather different from Optical Zoom.  With Digital Zoom the image is magnified by spacing out the pixels electronically, and as such is really very little different from blowing an image up to a larger size using a software package on your PC.  Digital Zoom has a detrimental effect on image quality, so depending on your application, you need to be careful how you use it.  

Digitizing
To convert an image into binary code. Visual images are digitized by scanning them and assigning a binary code to the resulting vector graphic or bit-mapped image data.

Digitizing tablet
A mouse replacement comprised of a "pen" and flat panel wired to the computer. Pen movements on the tablet are reproduced on the computer screen and pressing the tip of the pen against the tablet mimics pressing the mouse button. Some tablets may be pressure-sensitive in illustration programs like Photoshop -- a harder pressure makes a thicker line. Wacom brand pressure-sensitive tablets are favored over the mouse by many graphic artists.

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

Diodes
Light sensitive electronic components used in image capture. They function as one-way valves that sense the presence or absence of light and create a digital signal that the computer converts into pixels values.

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

Diopter 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 diopter correction can be a welcome option for eyeglass wearers.

Direct light
Light shining directly on the subject and producing strong highlights and deep shadows.

Direct Memory Access
The ability to use memory without a software interface.

Direct photo printing
A feature of some photo printers that allows users to transfer a memory card from a camera directly to a printer, enabling the images on that card to be printed without a PC.

Directory folder
In a graphical user interface, an icon resembling a yellow file folder where other files are stored for data organization. Directory folders are used to represent any drive or directory contents in the system.

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

Direct positive print
Made from a transparency without an internegative on a direct positive colour paper.

Disc
The spelling variation of "disk" referring to compact discs such as Photo CD or other CD-ROM.

Disk drive
A device that can contain a fixed or removable spinning disk used for storage of digital data.

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

Display technology
The type of technology used for desktop displays, such as CRT (cathode ray tube) or LCD (liquid crystal display). Other forms of display technology include LED (light-emitting diode) and gas plasma.

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.

Dithering
Altering the values of adjacent dots or pixels on a digital output device to create the appearance of a increased number of tonal values or colours.

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.

DMA (Direct Memory Access)
Allows the I/O subsystem to access main memory for the transfer of data.

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.

Dodge ( Dodging )
In photographic printing, to dodge a print is to reduce the exposure in a section of the image to make that area lighter. Compare this to the technique of burning.

Domain
An area of a network over which administrative control is exercised. The primary domain is the file server for all clients.

DOS ( Disk Operating System)
The main system software that tells your computer how to work.

Dot
The smallest raster element of an image. Many dots together produce one pixel. Meaning, for example, that in the specification "8 bit depth", three "layers" of 256 dots each are on top of one another to produce one pixel.

Dots, halftone
Minute, symmetrical individual subdivisions of the printing surface formed by a half-tone screen.

Dot gain
A printing defect in which dots prints larger than intended, causing darker colours or tones.

Dots per inch (dpi):
Measure of output device resolution and quality. For example, the number of pixels per inch on a display device. Measures the number of dots horizontally and vertically.

Dot pitch
The distance between the dots on a computer monitor, typically 0.2 to 0.3 millimeters. The closer the dots the sharper the image on the monitor.

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

Download
The process of receiving data from another digital source.

Downsize
To reduce the file size of an image, by lowering the resolution and/or reducing the square measurement of the file.

Down-sampling
The reduction in resolution of an image, necessitating a loss in detail.

DPI
Dots per Inch. A measurement of resolution or fineness for a printer or scanner. A dot is the smallest unit that can be displayed, scanned, or printed. If a device has a resolution of 300 dpi, it means there are three hundred dots horizontally and three hundred dots vertically. The higher the number of dots per inch, The greater the amount of detail that can be present in the image. If all other image-quality factors are equal, the more dots per inch the better. However, with greater dpi, comes larger file-size and/or longer display and printing times.

DRAM
DynamicRandomAccessMemory. A particular type of RAM that requires constant attention from the computer in order to retain data in storage.

Drag and drop
The process of moving text, graphics, or photos to different locations in a document.

Drive speed
The speed (RPM) That a drive mechanism rotates. Faster drive speeds allow for faster data transfer.

Driver
A software utility designed to tell a computer how to operate a external device. For instance, to operate a printer or a scanner, a computer will need a specific driver.

Drum scanner
A high-quality image-capture device. The image to be capture is wrapped around a drum that spins very fast while a light source scans across it to capture a digital version of the image.

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.

DSP (Digital Signal Processor)
Chips that are designed to facilitate digital video and audio, along with accelerating image processing.

Dual processors
Two central processing units in the computer.

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

Duplex
The ability of a scanner to scan both sides of a sheet simultaneously. Requires two scanner cameras and often two processing boards.

DVD
" Digital Video Disk " An optical storage medium that can store up to 4.7 Gigabytes ( single layer ), 8.5 GB (double layer ), 9.4 GB (double sided, single layer ), or 17 GB (double sided, double layer ). Transfer rates and seek times are similar to those of CD-ROM for currently available drives. The DVD spec included higher level specs for audio and video capabilities.

DX-coding
A checkered or bar code on some film cassettes. The checkered code can be automatically scanned by suitable equipment for such information as film processing equipment for film type, processing procedure, and so on.

Dye-sublimation printer
A type of continuous tone printing process a vibrant 300ppi colour print. The pixels are printed by a thermal print heat that sublimates (vaporizes) the dye from a coloured saran wrap like ribbon onto the dye-sublimation paper. The hotter the element on the thermal printed head, the darker the spots of colour.

Dynamic range
The ability of a scanner to register a wide range of tonal values--something from near white to near black. A scanner with good dynamic range is able to map input shades correctly to output shades, making images look brighter and giving them more visible detail. Generally the number of bits determines the maximum dynamic range of a scanner. For example a 36-bit scanner has a higher dynamic range than a 24-bit scanner.

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- E -

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

Easel
A holder to keep sensitized material, normally paper flat and in position on the baseboard of an enlarger during projection printing. It usually has adjustable borders to frame the image to various size.

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

Effective resolution
The final appearance of a scan that has been enhanced to produce more data than the scanner can record. This is done by interpolation.

EI
see exposure index

EISA bus
Eisa is a standard bus ( computer interconnection ) architecture that extends the ISA standard to a 32-bit interface.

Electronic display
Showing images through the computer.

Electronic Document
A document that has been scanned, or was originally created on a computer. Documents become more useful when stored electronically because they can be widely distributed instantly, and allow searching. HTML and PDF are well known electronic document formats

Electronic flash
A small device usually built into digital cameras that emits a brief burst of light to illuminate poorly lit scenes.

Electronic media
Any of the media used to publish information electronically (as opposed to print). Some examples are: presentation packages, annotated image catalogues, World Wide Web pages.

Electronic publishing
Composition of text (and frequently graphic images) using a computer for display in a computer presentation program or on the World Wide Web.

Electronic retouching
Enhancing a computer images with editing software.

Elliptical dot
A type of halftone screen dot with an elliptical rather than circular shape, which sometimes produces better tonal gradations.

Embedded profile
An ICC profile stored inside a TIFF, EPS, PDF, PSD, image, defining the colour space in which the image data are interpreted.

Embossing
Applying a special effect to an image that gives it a 3-D, embossed-looking surface.

Emulsion
The light-sensitive layer of film or paper. In black and white films the emulsion usually consists of very fine grain of silver halide suspended in gelatin, Which blacken when exposed to light. The emulsion of colour films contains molecules of dye in addition to the silver halide.

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.

Encryption
A technique used in preventing unauthorized third parties from viewing information that you are uploading or downloading. Encryption is most commonly used when credit card information is being transmitted. When encryption is used, the data being sent is split into sections and each section is sent through different connections. The two most common encryption patterns are 56-bit and 128-bit (the higher the number, the more secure the connection is).

Enhancement
The improvement of an image either through colour and/or density change.

Enlargement
An image, usually a print that is larger than the negative. Made by projecting an enlarged image of the negative onto sensitized paper.

Enlarger
An optical instrument ordinarily used to project an image of a negative onto sensitized paper. More accurately called a projection printer because it can project an image that is either larger or smaller than the negative.

Enlarger head
The part of an enlarger that contains the light source, the negative carrier and the lens. An enlarger head also houses a filter drawer or a built-in filtration system.

Equalization
An image processing technique where the range of tones or colours in an image file are expanded in order to produce a more pleasing image.

Erase
The process of removing information from memory or storage. Part of a file or image may be erased.

Eraser
This tool is used to change the current colour of piels to the background colour.

EV
Exposure Value. Developed in order to simplify numbers used in exposure calculations. Currently used to describe the range of exposure in which equipment can successfully operate.

Exabyte
A type of 8mm tape drive and storage cartridge.

Exif
Exchangeable Image File: the file format used by most digital cameras. For example, when a typical camera is set to record a JPEG, it’s actually recording an EXIF file that uses JPEG compression to compress the photo data within the file.

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.

Expansion memory
A method for fooling the computer into using more than the maximum 640K of RAM most personal computers are designed to use.

Expansion board
A circuit board that fits into an expansions slot located on the motherboard . Some adapter boards come installed in the computer, and others may be purchased at a later time to upgrade or add abilities to the computer.

Expansion slots
Female slots located on the motherboard into which the male pins of an expansion board fit.

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.

Export
The process of transporting data from one computer, type of file format, or device to another.

Exposure
1. The act of letting light fall on a light sensitive material
2. The amount of light that passes through a lens (either a camera or photographic paper) to form an image. In the camera, too much light causes overexposure-this makes negative film look too dark and reversal film look too light. Underexposure (too little light) has the reverse effect. In enlarging, overexposure makes a print from a negative too dark and a print from a slide too light. Underexposure has the reverse effect.

Exposure Bracketing
Shooting the same subject at a range of different exposures. Some camera provides Auto Exposure Bracketing/Flash Exposure Bracketing.

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, in f-stop, that deviates from the optical exposure but will still produce acceptable results on a specific film.

Exposure meter
An instrument for measuring the intensity of light so as to determine the shutter and aperture setting necessary to obtain correct exposure. Exposure meters may be built into the camera or be completely separate units. Separate meters can sometimes measure the light falling on the subject (incident reading) as well as the light reflected by it (reflected reading) ; built-in meters measure only reflected light. Both types of meters may be capable of measuring light from a particular part of the subject (spot metering) as well as taking an overall reading. Commonly called a light meter.

Exposure setting
The aperture and shutter speed combination used to expose the film in a camera.

Exposure value
Refers to the ability to override the auto exposure system on a digital camera to lighten or darken an image.

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

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.

External modem
A modem that resides outside the computer, and that attaches to the computer's serial port by cable.

External flash
A supplementary flash unit that connects to the camera with a cable, or is triggered by the light from the camera’s internal flash. Many fun and creative effects can be created with external flash.

Eyedropper
This tool takes a sample of a colour from an image so that it can be used as the new background or foreground colour.

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.

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