444 Glossary
kelvin (K) A unit of measurement used to describe color values of light sources, based on a
temperature scale that begins at absolute zero. See also color temperature, white balance.
keywords Descriptive words about the subject in the image that are added to image
versions and saved as metadata. See also metadata.
lab plot A visual three-dimensional representation of the CIE Lab color space. See also
color space, ColorSync.
lens A series of sophisticated elements—usually glass—constructed to refract and
focus the reflective light from a scene at a specific point: the digital image sensor in a
camera. See also camera, digital image sensor, macro lens, prime lens, telephoto lens,
wide-angle lens, zoom lens.
Library In Aperture, a container file that holds projects, folders, albums, master files,
and versions. You organize the elements in the Library, rename items, sort them,
and so on, in the Projects panel. By default, the Aperture Library file is located at
Users/username/Pictures/. See also album, folder, master file, project, version.
light Visible energy in the electromagnetic spectrum with wavelengths ranging
between 400 and 720 nanometers. See also electromagnetic radiation.
light meter A device capable of measuring the intensity of reflective light. Light
meters are used as an aid for selecting the correct exposure settings on the camera.
Most cameras have internal light meters. See also center-weighted metering, evaluative
metering, meter, spot metering.
luminance A value describing the brightness of all color channels combined in a pixel.
LZW compression A lossless data-compression algorithm developed by Abraham
Lempel, Jakob Ziv, and Terry Welch in 1984. LZW compression algorithms are typically
used with JPEG and TIFF graphics files to reduce the file size for archiving and
transmission at a ratio of 2.8:1. See also compression, JPEG, TIFF.
macro lens A type of lens used for extreme close-up photography. See also camera,
lens,
prime lens, telephoto lens, wide-angle lens, zoom lens.
master file The source image file that was copied from either your computer’s file
system or your camera’s memory card. In Aperture, the master file is never modified.
Anytime a change is made to the image, that change is applied to the version. See also
memory card, project, version.
megapixel 1 million pixels. For example 1,500,000 pixels is 1.5 megapixels. See also
digital image sensor, pixel.
memory card The device in the camera where digital images are stored. See also
camera, capture.
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