Page 70 - Enhancing CAD Drawings with Photoshop

4386.book Page 53 Monday, November 15, 2004 3:27 PM

Chapter 2

Working with Color

As you learned in Chapter 1, color modes (RGB and CMYK, for example) were developed to deal with
the optics of additive and subtractive color in the real world. However, you know that the color of a
document you see on a computer monitor often appears differently when that document is printed.
Color varies between makes and models of monitors, scanners, cameras, printers, and printing
presses. Color rendition can change on the same device over time. People even perceive colors a bit
differently, and this effect can be pronounced under different lighting conditions. Therefore, it is
impossible to perfectly represent the same color everywhere.
The best we can shoot for is to produce consistent color and to make its representation as accurate
as possible on every device. You should be able to get close to the ideal of “what you see is what you
get.” To effectively work with color in Photoshop, you need to understand the following concepts and
techniques:

◆ Modes and Gamuts
◆ Color Spaces
◆ Calibration and Profiles
◆ Consistent Color Printing
◆ Professional Color

Modes and Gamuts
You have already been introduced to RGB and CMYK color modes. These modes represent color models,
or basic assumptions we make when dealing with color. In the RGB color model, red, green, and blue
are the three components. These are stored as three channels that combine to represent a wide range
of colors. The complete range of colors that a mode can display or print is called a gamut.
Each mode offers a different gamut of colors. Although there is a lot of overlap between color mod-
els, some RGB colors cannot be represented in CMYK, and vice versa. Colors that can be represented
in a given mode are considered “in gamut,” and those that can’t be represented are considered “out
of gamut.”
Photoshop’s internal color conversion engine uses a third color mode called Lab because it has a
larger range of colors encompassing both RGB and CMYK’s entire gamuts.
NOTE Lab color is actually an abbreviation for the CIE L*a*b* color model that was created by the
International Commission on Illumination (CIE is its French acronym), an organization devoted to
the issues relating to the art and science of lighting.