three primary colors, resulting in two addi-
tional signals to describe color. Combining the
three signals back together results in a full
color image. Note that in either case, if the
chrominance (color information) is ignored,
the result is a black-and-white picture.
■ CMYK—Color printers and large offset
printers rely on the CMYK color space. This
color space matches the color pigments
cyan, magenta, and yellow. The color black
(the K in CMYK) is included, but not
required. The colors C, M, and Y absorb col-
ors on paper, creating black. This differs
from the RGB color space, which reflects
white when the colors R, G, and B are com-
bined. For this reason, the CMY color space
is called a “subtractive model.” The black
(K) component is added so that true black
can be printed on paper (versus a contrived
black from the three colors).
As with the RGB color space, every color is represented by three values: C, M,
and Y. These values are assumed to be in the 0–255 range.■ CiéLAB—LAB color mode splits color into three values:
■ Ldescribes relative lightness
■ A represents relative redness-greenness
■ Brepresents relative yellowness-bluenessAdobe Photoshop software uses LAB color as its native color space because
LAB color can be converted to another color space without doing damage to
the colors’ intensities or hues. Photoshop is just as talented at working with
images in the other color spaces, of course. The RGB color space is actually
related closely to LAB color. The CiéLAB model was adopted worldwide as the
master color space definition in 1991.The color models described here are the most common color spaces. Digital cameras
rely on the RGB color space, which has a few issues. One is that the RGB color space
is device-dependent. In other words, when the camera captures an image, it may not
appear the same on the monitor (another RGB device). This, of course, could cause
problems for serious color photographers.16 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY
The JPEG compression
scheme relies on YUV,
which is also known as YCbCr.
This color space enables the com-
pression of the chrominance (col-
ors) in an image without affecting
the brightness. The human eye is
more sensitive to brightness
changes than color changes,
which fits with this color model.