brightness value of a single pixel in a gray scale image or a
single character (number or letter) in word processing.
calibration The act of adjusting the brightness and col-
ors of one device, such as a monitor, to match those of
another, such as a printer. Calibration may also be used to
simply adjust a device to some standard of performance.
CCD (charge-coupled device) In a digital camera, a
charged-coupled device is a light-sensitive silicon computer
chip that converts the light from the camera lens into elec-
trical current. The chip may have millions of separate sen-
sors, each of whose current reading is translated (by an
analog to digital converter) into a digital brightness value.
CD-ROM (Compact Disc, Read-Only Memory) A
nonrewritable compact disc used as a storage medium for
digital data.
CD-RW (Compact Disc, Rewritable) A rewritable
compact disc.
clipping In image capture with a scanner or digital cam-
era, an exposure error that causes a loss of information at
the highest and/or lowest brightness levels.
CMY Cyan, magenta, and yellow are three subtractive
color primaries. Used by some printing processes, notably
color photographic paper.
CMYK Cyan, magenta, yellow, and black are the colors
used in offset printing. Although CMY ideally would be a
better set of inks for printing, adding K (black) is a practical
necessity because CMY inks do not produce satisfactory
black tones by themselves.
color cast An unwanted color tint to an image caused
by exposure of the film or digital capture under inappropri-
ate lighting conditions.
color channel One of the ways information is organized
within an image. Color channels store the brightness values
of the pixels in each of the primary colors. Contrast with
alpha channels.
Color Management A software system designed to
deliver accurate color calibration and consistent color
matching among computer monitors, scanners, and any
output devices such as printers and offset presses.
color space A scientific description of a set of colors. A
color space numerically describes all the colors that can be
created by a device, such as a camera or a printer.
compression A software process in which image data is
“squeezed” to reduce the size of the image file. Compression348 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHYmethods can be lossless, as in compressed TIFF images, or
lossy, as in JPEG compression.
continuous tone printer A color printer whose smallest
color markings can be any of millions of distinct colors. Dye
sublimation printers are the most common type of continu-
ous tone printer.
data Anything put into, processed by, or stored in a com-
puter. Data can also be the input from a camera or scanner
or the output to a computer accessory, such as a printer or
modem.
default A predetermined setting in a computer program
that will be used unless the user chooses another.
device profile A database used by color management
software. It contains information about the actual colors
that a device (such as a monitor or printer) produces. The
color management software uses the information to ensure
that the device produces the desired colors.
digital camera A camera that captures an image on a
CCD chip and digitizes it so that it can be downloaded to a
computer or a digital printer.
digital image An image created by a digital camera or
a computer scanner. Digital images are composed of pixels.
digitization The process of converting analog informa-
tion into digital data that a computer can use.
disc or disk Te rms used to describe computer media that
store data on a revolving platter. Magnetic storage media
are called disks (floppy disks, Zip disks and hard disks),
while media that use lasers (CDs and DVDs) are called
discs.
dithering A process used by some types of printers to cre-
ate the appearance of millions of distinct colors from as few
as four basic (CMYK) colors. In dithering, nearly invisible
dots of each basic color are placed so close together (and
the basic colors mixed without any visible pattern) that the
eye is fooled into seeing a solid distinct color at that spot.
Inkjet printers are the most common dithering printer.
download To transfer files or other data from one piece
of computer equipment to another.
dpi (dots per inch) Originally, a measurement of the
resolution of a printer or monitor. A printer that can print
1,440 dots in a row in a single inch is a 1440 dpi printer.
dpi is often used interchangeably with other more accurate
terms: pixels per inch (ppi) is a measure of the number of
pixels (lined up in a row) per inch that appears on a moni-
tor or in a print. An image may have only 200 pixels per29 0789731207_glossary.qxd 4/6/04 2:16 PM Page 348