Graphics Programs Reference
In-Depth Information
Continuous Tone:
An unbroken, smooth, and uninterrupted tone making
up an image. Rather than seeing an actual series of dots or a mosaic of
dots or pixels, continuous tone describes how we humans see the world
before us. A photographic print is considered continuous tone. See also
Halftone
.
Contract proof:
A color proof that is supposed to match a final print con-
dition, usually a four-color press sheet. The proof is contractually agreed
by print buyer and print producer to match the final print conditions on
the press. A Kodak Matchprint is a common contract proof.
Contrast:
In its photographic definition, the differences in tones such as
the difference between the lightest and darkest parts of the picture or the
difference between the highlight and shadow of an image.
Contrast ratio:
The ratio between the brightest white and darkest black.
Correlated Color Temperature (CCT):
An obsolete method of defining white
illuminants. Lines of CCT are perpendicular to a theoretical curved line
through chromaticity space. This curve is plotted by heating a theoreti-
cal black body and predicting the chromaticity of the energy emitted
at various temperatures. These temperatures are reported using the
Kelvin scale. A common tungsten light bulb has a CCT of 2300 Kelvins
(2300 K). Daylight can vary from 3500 K to 13,000 K. An overcast sky at
noon is around 6500 K. Lower values have warm hues, higher values are
cool blues. It's important to understand that when using this system very
different illuminants can have the same CCT. It was for this reason the
CIE created the D illuminants, which have fixed chromaticities and
spectra. Many people don't mention CCT when they mean CCT; they will
often just say, 5000 K. See also
Illuminant
.
Cross-rendering:
The process where one printer is used to simulate the
color of another printer. Using color management to make an Epson
printer produce a proof that matches what will ultimately be output on
a contract proof is an example of cross-rendering. Also known as cross
simulation.
D50:
See
Illuminant
.
D65:
See
Illuminant
.
deltaE:
A unit of measure that calculates and reports the differences in
two samples. A deltaE of less than 1 is approximately unperceivable to
the human eye; a deltaE of 6 is considered an acceptable match. A deltaE
of 1 is considered a just-noticeable difference between two colors not
touching (the eye is more sensitive to changes if two colors actually
touch). The higher the deltaE, the greater the difference of the two
samples being compared. There are a number of ways in which deltaE is
calculated (deltaE, deltaE CMC, deltaE 2000, etc).
