Photographic Glossary-C


C 41
Kodak's standard chemical process for developing color negative film, an industrial reference standard.

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. Longer exposures allow camera shake to be noticed where it would not be at faster shutter speeds. In order to avoid this problem the camera is often placed on a tripod and a cable release is used to trip the shutter. A cable release has a threaded end that is screwed into the shutter release. This is making the assumption that the shutter release button is designed to accept a cable release. If the camera is not designed for a cable release, there is probably a different method, usually a remote control, either wired or IR, that is used for manual release.

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 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.

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.

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

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

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.

Electrical component once more commonly known as a condenser. Stores electrical energy supplied by a power source and can discharge it more rapidly than the source itself. Used in flash equipment, providing reliable bulb firing even from weak batteries, and supplying the surge needed for electronic flash tubes.

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

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

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.

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.

A light tight, factory-loaded film container that can be placed in and removed from the camera in daylight. Some nature of film, like the infra red film, MUST not even try to load or unload film in any possible light existence, absolutely must be in total pitch dark condition to avoid fogging on film.

Light-trapped film container used with 35 mm cameras.
Elliptically shaped film cassette designed especially for the Advanced Photo System that serves as the sealed, leaderless container for all System film whether unexposed, exposed or processed.

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. Abnormal colouring of an image produced by departure from recommended exposure or processing conditions with a transparency film, or when making a colour print. Can also be caused by reflection within the subject as from a hat on to the face.

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

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.

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.

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.

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

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

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.

Cadmium Sulfide (Cell). A battery powered, current-modulating. light-sensing cell that was quite popular with lots of cameras exposure metering system and external metering devices. May be this extra will help, photo conductive material used in exposure meters as alternative to selenium-based or silicon blue photocells. Its electrical resistance decreases as the light falling on it increases. Cds meters use current from an external power source, such as a battery.

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.)

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

CRC (Close Range Correction System): Check Nikon's terms page for more. (2)"Classic" format - one of the three selectable Advanced Photo System print formats; identical to the 2:3 aspect ratio used in 35 mm photography and suitable for most general-purpose shots.

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.

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.

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.

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.

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
A lens aberration producing an overall blurred image; the inability of a lens to bring all wavelengths of light (especially red and blue) into the same plane of focus; usually present in regular large-aperture telephoto and super-telephoto lenses; does not improve by stopping down the lens; correctable through the use of low Dispersion (ED, LD SD) glass. Basically, this aberration is caused by light rays of different wavelengths coming to focus at different distances from the lens. Blue will focus at the shortest distance and red at the greatest distance. Since the natural rays of light are a mixture of colors, each aberration will give a different value corresponding to each color thus producing blurred images. 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.

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

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

Chromogenic Film
These include Black & White films which are designed to processed in C-41 (color) chemistry. Example: Kodak CN400, Ilford XP-2.

Contrast Index (sounds like composite index for stock market, ha!) Numeric rating indicating the optimum development contrast for negative materials.

A process by which a photographic print is made directly from a color transparency. Noted for rich color, brilliant clarity and unprecedented archival quality for color prints. Also called Ilfochrome. 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 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.

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

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 neutralises hypo in film or paper, reducing wash time and helping to provide a more stable image.

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.

Click stop
Ball bearing and recess or similar construction used to enable shutter speeds, aperture values, etc. to be set by touch.

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

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.

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

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.

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.

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

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

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.

(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.

A threaded means of mounting a lens to a camera.

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

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

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

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

Color Densitometer
A piece of equipment used by press personnel to determine the density of the ink color being laid down on the printed sheet. It has a numerical digital read out and the higher the readout on the densitometer, the greater the amount of ink that is being laid down on the sheet.

Color Temperature
Film is often referred to by the color balance for which it is designed. As a general rule, the higher the number, the greater the blue hues; the smaller the number, the greater red hues. Fluorescent lighting fills a range from 3500 K to 6200 K depending on its use. Flash tubes are often daylight balanced.
5500 K: Daylight balanced
3800 K: Tungsten balanced.

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

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, etc.

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

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

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

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

Colour engine
The colour matching method used in a colour management system to convert the image data from the colour space of the source profile to the colour space of the destination profile.

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

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

Colour intensity
A feature found on most inkjet printers that controls the brightness of an image by varying the amount of ink applied to the page; lighter images use less ink and darker images use more.

Colour management
System that attempt to produce consistency in the representation of colour in image files, across image capture, display, and output devices.

Colour match RGB
The RGB working space that is the native colour space of Radius Press view monitors. This space provides a smaller gamut alternative to Adobe RGB (1998) for print production work.

Colour model
A colour measurement scale or system that numerically specifies the perceived attributes of colour. Used in computer graphics applications and by colour measurement instruments.

Colour negative
Film designed to produce colour image with both tones and colours reversed for subsequent printing to a positive image, usually on paper. Film processed as a negative image from which positive prints can be made.

Colour Palette
Things are displayed on your monitor according to a specified number of colours in a color palette, e.g.: 256 colours. The theory is that more colours = more vivid picture quality. The number of colours a display is set to effects the entire look of the desktop, and correspondingly, the way applications look.

Colour passes
The number of times the carriage assembly of a scanner must pass over an object in order to achieve it's full potential colour depth.

Colour picker
The colour picker allows you to choose or define colours for the background or foreground colours using a colour spectrum or numerical values.

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 profile
A representation of the colour properties of a device; colour space. Today, virtually all profiles conform to the ICC specification.

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

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

Colour sensitivity
Response of a sensitive material to colours of different wavelengths.

Colour separation
Conversion of RGB colour information into its cyan, magenta, yellow and black constituents.

Colour space
Colour spaces describe how the red, green and blue primaries are mixed to form a given hue in the colour spectrum. Since it is not possible to represent every colour in the visible spectrum *exactly* by mixing amounts of red, green and blue, colour spaces allow us to change how we define red, green and blue (and white) to get better colour reproduction. By "tweaking" primaries in this way, we can maximize how many colours *can* be accurately represented on monitors, printers, etc. by matching the colour space closely to what the device is capable of reproducing. There are also colour spaces designed for photo editing that don't match *any* particular device, but are instead designed to give more "coverage" of the overall colour gamut (spectrum of visible light) for the purpose of photo editing.

Colour temperature
Description of the colour of a light-source by comparing it with the colour of light emitted by a (theoretical) perfect radiator at a particular temperature expressed in Kelvin (K). Thus "photographic daylight" has a colour temperature of about 5500K. Photographic tungsten lights have colour temperatures of either 3400K or 3200K depending on their construction. The temperature (measured in degrees Kelvin) to which an object would have to be heated before it would radiate a given colour. Each type of light can also be represented by a numerical colour temperature, here are the (rough) colour temperatures of typical lighting conditions.

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 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.

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

A lens aberration restricted to off axis image points; the inability of a lens to render point sources of light near the edges of the frame as circular; the points of light appear as comet-shaped blurs (hence the name coma) with the tails flaring toward the center of the image; this aberration is very difficult to eliminate in wideangle lenses with large maximum apertures; improves by stopping down the lens.

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. Most digital cameras with PC Card interfaces use a storage technology called CompactFlash. Standard supported by the CompactFlash Association. CompactFlash is ATA compatible and will fit into any Type II or Type III slot when used with a passive adapter.

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. Under some circumstances there may be a need to shoot film at an Exposure Index other than the ASA rating on the film. This technique is known as push or pull processing. Color Print films are not advisable to alter EI ratings but it can be done. Slide film and black and white can be pushed and pulled with fairly good results. Push processing involves rating the film at faster than recommended and then increasing development time because less light has exposed the film. This will increase the contrast in the final image. Pull processing the film is exposed at a slower setting and development time is decreased. Images produced from pull processing should have an increased tonal range.

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.

Part of a compound lens consisting of one element (single lens) or more than one element cemented or otherwise joined together. A lens may therefore be described as 4-element, 3-component when two of the elements are cemented together.

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

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

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

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.

Computerised flash
Electronic flash guns which sense the light reflected from the subject, and cut off their output when they have received sufficient light for correct exposure. Most units must be used on or close to the camera for direct lighting only. And the camera lens must be set to a specific aperture (or a small range of apertures) determined by the speed of the film in use.

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. An enlarger with a sharp, undiffused light that produces high contrast and high definition in a print. Scratches and blemishes in the negative are emphasised.

An optical system which concentrates light rays from a wide source into a narrow beam. Condensers are used in spotlights and enlargers. Generally a simple lens used to collect light and concentrate it on a particular area, as in enlarger or projector. Frequently in the form of two planoconvex lenses in a metal housing. A condenser, normally of the Fresnel type, is used to ensure even illumination of the viewing screens on SLR cameras.

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

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
A print made by exposing photographic paper while it is held tightly against the negative. Images in the print will be the same size as those in the negative. Also known as proofs, contact prints involve placing the negative directly on to the photographic paper and printing this way. The print is then an exact copy of the negative, except now it is a positive that can be used for quick viewing.

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

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

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

Continuous Servo (Nikon's term)
AF Focus detection continues as long as shutter release button is lightly pressed and the reflex mirror is in the viewing position. Useful when the camera-to subject distance is likely to change.

Continuous Servo AF Focus
Autofocus term used by Nikon, the AF sensor detection continues as long as shutter release button is lightly pressed and the reflex mirror is in the viewing position. Useful when the camera-to-subject distance is likely to change.

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

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 image
An image containing gradient tones from black to white.

Another name for banding or posterization.

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.

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. The range of difference in the light to dark areas of a negative, print, or slide (also called density); the brightness range of a subject or the scene lighting. It may be also explained as tonal difference. More often used to compare original and reproduction. A negative may be said to be contrasty if it shows fewer, more widely spaced tones than in the original. Or another way to explain, a difference in visual brilliance between one part of the image and another; without contrast, there would be no such thing as a visible image; a line in a photograph is visible only because it is either darker or lighter in tone than the background; every distinguishable part of the image is the result of a contrast in tonal values.

Describes a scene, negative, or print with very great differences in brightness light and dark areas. Opposite: flat.
Higher-than-normal contrast including very bright and dark areas. The range of density in a negative or print is higher than it was in the original scene.

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

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.

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

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.

Correction of Aberrations at Close Distance Focusing (or CRC)
In general, lenses are designed for maximum performance at infinity. Accordingly, when the lens barrel is fully extended to the shortest focusing distance, resolution is reduced. Although this is negligible for ordinary lenses, it becomes increasingly important in lens specially designed for close distance photography. Lens designers adopted a system where mechanism moves certain lens components as a unit automatically correcting for aberrations. This assures high lens performance throughout the focusing range.

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.

CP filters
Abbreviation for colour printing filters.

CPU ( Central Processing Unit)
The electronic component that controls an electronic product's functions. Essentially, all automatic cameras have at least a CPU to control various functions of the cameras. Some top models have three to five CPU to handle individual task functions - some handle the exposure, one handle the autofocus and so on. The latest on some top models utilising 8 or 16 bits chips now. Newer autofocus lenses have built-in CPUs to relay information relating to focal length, distance info, lens type to the camera body for exposure to AF processing.

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. Printing only part of the image that is in the negative or slide, usually for a more pleasing composition, in medium format, esp the 6 x 6, some form of cropping is necessary for publishing on A4 magazine format. May also refer to the framing of the scene in the viewfinder.

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.

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.

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

A location marker or pointer on the monitor.

Curvature of Field
This optical defect causes points on an object plane perpendicular to the lens axis to focus on a curved surface rather than a plane. 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.

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

Cyanotype and Vandyke
These methods, and others, made from metals combined with their ferric salts (platinum, palladium, gold, copper, etc.) can produce infinite monochrome variations with capacity to convey special moods.