Contex XD2490 Service Manual page 40

CALS
Computer-aided Acquisition and Logistics Support (CALS)
standard, a U.S. Defense Department and industry initiative
that addresses the design, manufacture, and support issues of
generation, access, management, and use of technical data in
digital form.
CCD
Charge Coupled Device, CCD is the image sensor in the scan-
ner that converts light to voltages. These voltages are convert-
ed by the scanner into the image.
CCITT Group3
Standard runlength compression format used with FAX
transmission. It utilizes modified Huffman coding to further
compress the runlength numbers. Most scanner file formats are
dialects of this format.
CCITT Group4
Two-dimensional compression format, giving very compact
image files. Standardized by CALS (MIL 28002) and ISO-
ODA for Drawing Archival and Interchange.
CIE LAB
A device-independent color space specified by CIE, used in
modern color management software to facilitate conversion of
data from a scanner to a display, or from a display to an output
device.
CIE
Centre Internationale d'Eclairage (CIE) is an international or-
ganization that establishes methods for measuring color. These
color standards for colormetric measurements are internation-
ally accepted specifications that define color values mathemati-
cally. The first color space model, the CIE xyz, was developed
in 1931. CIE defines color as a combination of three axes: x,
y,and z. The two color spaces released in 1978 are CIE Lab
and CIE Luv. The goal was to provide an accurate and uniform
reference of visual perception.
CMYK
The subtractive printing colors. Cyan, Magenta, Yellow, Black.
Color Balance
The visual effect of an image when the amount of each color
and the overall amount of color are balanced.
Color bit depth
The simplest pixel has two options: black or white. (A pixel
with two choices is known as a 1-bit image, or two raised to
the power of one). Adding more bit information increases the
C-2
Appendix - C --- Scanner Terms
number of color options. The number of potential color options
for a pixel is called color bit depth. For example a 4-bit pixel
would have 16 color options, and an 8-bit pixel would have
256 color options, while a 24-bit pixel would have 16,777,216
color options.
Color Cast
An image is said to have a color cast if its colors are not true.
A color cast will usually be described by stating the particular
color predominant in the image, e.g., the grass appears to have
a red color cast.
Color Correction
To improve the color rendition. Correcting for, and eliminating
an unwanted color cast.
Color Management System
Color Management System (CMS) software increases the
accuracy of color interchange between scanners, displays
and printers based on profiles for each device. The CMS is
a layer of software resident on the computer that negotiates
color reproduction between the application and color devices.
The CMS performs the color transformations necessary to
exchange accurate color between diverse devices. The Color
manager needs access to characterization data for the device.
The format and content of such device profiles is standardized
by the International Color Consortium (ICC.)
Color Separation
Process of separating colors, in an image, into primary color
components for printing. Converting an RGB color image into
CMYK color image. Color separation is a technical function
during which critical settings such as GCR, black ink limit and
total ink limit are applied to the image.
Color Space
A color space is a particular language used to describe color.
Examples of color spaces are: RGB, CMYK, HSV, CIE LAB.
Contrast
The difference between the lightest and darkest significant
areas in a picture. A picture with high contrast has nearly white
areas and nearly black areas with sharp changes in brightness
between them. The picture seems dominated by stark light and
dark tones.
Density units
Photographers and printers measure transmission in base-10
logarithmic density units, where transmission of unity corre-
sponds to a density of 0, transmission of 0.1 corresponds to a
density of 1, transmission of 0.01 corresponds to a density of