CIRCLE OF ILLUMINATION The total image area of a lens, only part of which is actually used in taking a picture.

CLOSE-UP A photograph or a motion-picture scene taken at a very close range that shows intimate detail and captures and holds audience interest.

COATING, LENS A thin, transparent coating applied to the surface of lenses or other optical parts to reduce reflection.

COINCIDENCE Agreeing as to position. In a coincidence type of range finder, when the two half images of a distant object are in exact juxtaposition, they are said to be in coincidence."

COLLIMATED A beam of light is said to be collimated when all of its rays have been made parallel. See SPECULAR.

COLOR BALANCE The relationship between the three images composing a color negative or positive that provides an accurate (or, more generally, the most pleasing) reproduction of natural colors. (PIA)

COLOR BARS A color standard used by the television industry for the alignment of cameras and videotape recordings.

COLOR CHART Target for test photography composed of pigmented areas having colors of high saturation, often accompanied by gray scales, and useful in both color photography and in black-and-white reproduction of colored objects. An assembly of chromatic samples illustrating a scheme of color classification. (PIA)

COLOR COMPENSATING FILTER A filter used to change the overall color balance of photographic results obtained with color film and to compensate for deficiencies in the quality of the light when printing color films.

COLOR TEMPERATURE The temperature to which a black body radiator must be raised in order that the light it emits may match a given light source in color; usually expressed in degrees Kelvin (K).

COLOR TEMPERATURE METER An instrument for estimating the spectral quality of a light source or the illumination on a scene and expressing the value in terms of color temperature. (PIA)

COLOR TRANSPARENCY A positive image in natural colors on a transparent support intended for projection or for viewing by transmitted light. (PIA)

COLORBLIND Applied to photographic layers having only natural silver halide sensitivity to blue, violet, and ultraviolet rays. (PIA)

COMA An aberration of a lens that causes oblique pencils of light rays from an object point to be imaged as a comet-shaped blur.

COMPONENT The processing of RGB (red, green, and blue) channels as three separate channels.

COMPOSITE SIGNAL (Y/C) (Also called NTSC signal.) The video signal in which luminance Y (black and white) and chrominance (red, green, and blue) and sync information are encoded into a single signal.

CONJUGATE DISTANCE The distances of object and image from the lens are called conjugate distances. For every position that an object may occupy with respect to a lens, there is a corresponding position for the image.

CONTACT PRINT Print produced by exposure in immediate contact with the original or negative. These prints are the same size as the original or negative.

CONTAMINATION Foreign matter in a processing solution which impairs its operation.

CONTINUOUS TONE Photographs in which the detail and tone values of the subject are reproduced by an infinite gradation of gray densities between white and black. (PIA)

CONTRAST, LOW A term expressing a relationship of image tones in which highlights and shadows are represented by very little difference in densities.

CONTRASTY Photographic term applied to images showing accentuated highlights and shadows. (PIA)

CONTROL TRACK The area of the videotape used for recording the synchronization information (sync spikes).

COPY (l) Any document or photograph to be reproduced. (2) The results of such reproduction. (3) (Verb) The act of reproducing a document.

COPYBOARD The board, frame, or other device for holding copy to be photographed.

CORROSION The erosion of metals, as by the action of an acid or an alkali; rusting; oxidation. (PIA)

COUPLER Chemical compound in color developer that can react with the oxidized developing agent in the sensitized material to form a dye color.

CRITICAL FOCUS That point of focus at which resolution is at its maximum. (NMA)

CROP To trim or cut off parts of the picture by printing methods to eliminate superfluous portions, and thus improve the composition.

CROP MARKS Markings placed on original copy, indicating where part of the top, bottom, or sides of the picture are to be omitted.

CURVATURE OF FIELD An aberration of a lens that causes the image of a plane to be focused into a curved surface instead of into a plane.

CUTAWAYS (MOTION PICTURE) Shots of related and previously established outside interest used to divert the audience attention in order to cover jumps in action, screen-direction changes, and passage of time.