210 Glossary
compression ratio that’s produced, the greater the loss of image
quality and sharpness you can expect. Unlike other compression
schemes, JPEG is a “lossy” method. By comparison, LZW, com-
pression used in fi le formats such as GIF, is lossless—meaning
that no data is discarded during compression.K In the computer world, K stands for 2 to the 10th power, or
1,024. A kilobyte (or KB) is, therefore, not 1,000 bytes, but
rather, 1,024 bytes.Keyword A word that identifi es certain characteristics of a
photograph for later searching with a photo-organizing, or
imagebase, program. A good imagebase program should be able
to add keywords to your photographs and then be able to search
for the images that have those words associated with them.Landscape (mode) An image orientation that places a photo-
graph across the wider (horizontal) side of the monitor or
printer.Layer In image-enhancement programs, such as Adobe Pho-
toshop, layers are any one of several on-screen independent
levels for creating separate—but cumulative—effects for an
individual photograph. Layers can be manipulated indepen-
dently, and the sum of all the individual effects on each layer
makes up what you see as the fi nal image.
LZW Lempel-Ziv-Welch. A compression algorithm used by
Adobe Photoshop to perform lossless compression on TIFF
fi les.Magneto-optical This class of removable drives uses the
ability of lasers to heat material, and thus change refl ectivity, to
produce storage media that can be erased and reused. One of the
negatives of optical drives is that writing data to optical media
requires three spins. The fi rst spin erases existing data, the
second writes new data, and the third verifi es that the data
is there. When compared to magnetic drives, all this spinning
tends to reduce performance. Typical performance specifi cations
for magneto-optical drives are seek times of 30 ms, access time
of 40 ms, and average write transfer rate of 0.44 second. The
drives are more expensive than magnetic drives, although the
media is less so. Just as with their magnetic competitors, manu-
facturers have yet to standardize on a single magneto-optical
format.
Mask Many image-enhancement programs have the ability to
create masks—or stencils—that are placed over the original
image to protect parts of it and to allow other sections to be
edited or enhanced. Cutouts or openings in the mask make the
unmasked portions of the image accessible for manipulation
while the mask protects the rest.