GLOSSARY 351RAM (random access memory) The silicon chips that
are used to contain the computer’s memory. The memory is
used to hold and process the software programs, data files,
and commands that the computer is currently using.
Generally, the more RAM that a computer has for image
processing, the more quickly the editing can be accom-
plished.
raster image Raster images (also called bitmaps) are
made up of rows and columns of pixels.
resample To change the pixel dimensions of an image.
For example, to downsample an image from 2000× 1000
pixels to 500×250 pixels, or to upsample an image from
400 ×600 to 800×1200 pixels. Resampling permanently
alters the image.
resize To alter the physical size of an image (how big it is
printed or how large it appears on the monitor) without
resampling its pixels.
resolution Resolution determines the apparent sharpness
of an image. Resolution is the number of pixels per inch (or
other measure, like millimeters) in an image. For example,
an image printed 8×10 inches with 200 pixels per inch will
appear much sharper than an 8×10 print printed with 30
pixels per inch. When the capabilities of printers are dis-
cussed, the resolution of the printer is described as the num-
ber of dots per inch that the printer can put on the paper.
Seedpi.
RGB Red, green, and blue; the primary additive colors of
photography and digital imaging. Computer monitors cre-
ate images using the RGB colors.
samples per inch The number of times per inch that a
scanner samples an image. Note, however, that if a scanner
records 2,000 samples per inch, but its software enlarges the
image by 10 times, the final image will have only 200 pix-
els per inch. Seedpi for related information.
saturation The degree to which a color is pure and undi-
luted by light of a different hue. If a color is 100% satu-
rated, it contains no light of another hue. If a color has no
saturation, it appears gray, with no apparent hue. One of
the three terms used to exactly describe a color (the others
are brightness or value and hue).
scanner A device that converts photographs (on film or
on paper) into digital form so they can be stored in a com-
puter and edited by software.screen lines per inch Also referred to as lines per inch.
Used in the offset printing industry, lines per inch refers to
the number of rows or columns of halftone dots (a “screen”)
appearing in each inch of the printed matter. Do not con-
fuse screen lines per inch with dots per inch (seedpi).
selection A part of the area of a digital image that has
been isolated from the rest of the image for the purposes of
editing operations, such as changes to color or tones. A
variety of software tools are used to indicate to the com-
puter which area is to be selected.
service bureau A retail business that offers a variety of
computer-related services. Many have extensive imaging
capabilities, such as scanning, printing, and rental comput-
ers with imaging software. Some offer offset printing serv-
ices that may include the production of large negatives.
subtractive colors Cyan, magenta, and yellow are the
subtractive colors of photography and digital imaging.
When equal amounts of cyan, magenta, and yellow inks
are mixed on a sheet of white paper, a gray or black tone
results.
TIFF (Tagged Image File Format) A file format for
bitmap images that is readable by all major imaging soft-
ware programs. TIFF allows moderate amounts of lossless
compression.
unsharp masking A software process that increases the
apparent sharpness of an image. Actual image detail is not
increased.
vector image An image formed without pixels. Lines
and solid-filled areas are created by specifying the location
of line endpoints and the positions of lines (straight or
curved) between them. Adobe Illustrator creates vector
graphics, and there are some vector elements (such as
paths) in Adobe Photoshop that coexist with the bitmap
features.
virtual memory disk Space on a hard drive that is used
as a substitute for RAM by image-editing software when the
software runs out of real RAM. Because hard disks operate
more slowly than RAM, using virtual memory slows the
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