Glossary 207Gamut Range of colors that a printer, monitor, or other com-
puter peripheral can accurately reproduce. Every device from
every manufacturer has a unique gamut. If you fi nd that the
output of your color printer doesn’t match what you see on your
screen, you are beginning to understand the need for color man-
agement. The image may be “in gamut” for the monitor, but not
for the printer.
Gaussian Blur Adobe Photoshop’s fi lter gets its name from
the fact that this fi lter maps pixel color values according to a
Gaussian curve. A Gaussian curve is typically used to represent
a normal or statistically probable outcome for a random distribu-
tion of events and is often shown as a bell-shaped curve.
GIF (pronounced like the peanut butter) Graphics Inter-
change Format. A compressed-image-fi le format that was origi-
nally developed by CompuServe Information Systems (www.
cis.com) and is platform independent. The same bitmapped fi le
created on a Macintosh is readable by a Windows graphics
program.
Gigabyte One billion bytes or (more correctly) 1,024
megabytes.
Grayscale Series of gray tones ranging from white to pure
black. The more shades or levels of gray, the more accurately an
image will look like a full-toned black-and-white photograph.
Most scanners will scan from 16 to 256 gray tones. A grayscale
image fi le is typically one-third the size of a color one.
GUI Graphical User Interface.
HDR High Dynamic Range. A photograph’s dynamic range
is the ratio of contrast, tonal range, or density between black
and white, and can literally be interpreted as the range of f-stops
that can be captured, from a clean white to total black. Some
photographers may recognize these tonal areas as what Ansel
Adams’s Zone System calls Zones IX and 0. The concept behind
HDR is the ability to use a technique that can create an image
whose overall tone values match the luminance of what the
human eye records—not what a computer screen or print repro-
duces. Luminance is the brightness or grayscale level of a
color. Together with chromaticity, luminance defi nes a perceived
color.
ICC International Color Consortium. Group of eight large
manufacturers in the computer and digital imaging industries.
The consortium works to advance cross-platform color com-
munications and has established base-level standards and
protocols, in the form of ICC Profi le Format specifi cations, to
build a common foundation for communication of color
information.