Graphics Programs Reference
In-Depth Information
to the rays from the source. Luminance is measured using foot-lambert,
a unit equal to one lumen per square foot. The SI (Systeme International
d'Unites, an international system) is candela per meter squared, which
represents a luminous intensity of one candela radiating from a surface
whose area is one square meter. Luminance should not be confused with
brightness, which is a perceived and subjective attribute of light. See
http://www.crompton.com/wa3dsp/light/lumin.html.
LUX:
Lumens per square meter; a unit of illumination.
Metamerism:
A phenomenon whereby two color samples of differing
spectral properties can appear to match when viewed in one illuminant,
but appear differently under another illuminant. Keep in mind that
metamerism is also an effect whereby two colors of different objects of
differing spectral properties can appear to match appearance (which is a
good thing indeed).
Optical brighteners:
A fluorescent compound found in materials that
absorb invisible ultraviolet light and reemit it as visible light (usually in
the blue part of the spectrum), producing a brighter appearance from that
material (usually a paper) than really exists.
Optical density:
A value that is used to describe the ability of a material
(usually transmissive) to absorb light, the blackness of the darkest area
of a print, for example.
Output profile:
An ICC profile based on some type of output device such
as a printer or press.
PCS (Profile Connection Space):
An integral part of the ICC specification
used for converting from one device-dependent color space to another
device-dependent color space. The PCS color space is based on CIELAB
and thus can scientifically define all human color vision. The PCS is the
universal translator that allows color space conversions to be carried out
from source color space to destination color spaces.
Perceptual intent:
See
Rendering intent
.
Phosphors:
Chemicals that emit light when excited by different forms of
radiation such as electrons in a CRT or the UV radiation of mercury
plasma in a florescent tube. The phosphors that coat the inside of a CRT
display emit light when struck by an electronic beam to produce color.
There are three different phosphors used in a CRT: one each for red,
green, and blue.
Pipeline:
A new term used to better define what some call work flow;
coined by Pixel Genius Jeff Schewe. Pipeline is the long process used to
describe how we deal with images from capture all the way to output.
Pixel:
The basic building block of all digital images. The pixel (short for
picture element) is the individual square color and or tone that makes
up a mosaic we see as an image.
