Page 73 - Enhancing CAD Drawings with Photoshop

4386.book Page 56 Monday, November 15, 2004 3:27 PM
56 CHAPTER 2 WORKING WITH COLOR

12. Press Shift+Ctrl+Y to toggle Gamut Warning display back off.
13. You can close this file without saving.
Be aware of the potential for out-of-gamut colors so you don’t get any color surprises when you
print your images.
NOTE You can convert directly from RGB to CMYK (or vice versa) without manually entering Lab
mode as a separate step. Photoshop automatically makes the color conversion using Lab color inter-
nally. You can use Lab color intentionally in advanced retouching, as you will learn in Chapter 3.

Color Spaces

To make matters more complicated, each color model has many color spaces that can be used. Color
spaces are narrower portions within a color model representing a specific gamut.
For example, millions of colors can be stored in a 24-bit RGB image. However, a specific RGB print
device might only be capable of reproducing several hundred thousand colors. Each device’s gamut
defines its own specific color space within the RGB model.
Every device operates within its own color space. Every type of paper also has its own color space,
because media absorb color differently. Color spaces that characterize devices or media are stored in
profiles.
NOTE You will learn how to calibrate your monitor and create its color profile in the next section.
Since each device has its own color space, you might be wondering how Photoshop can ever
maintain consistency in this cacophony of color. The real secret is Photoshop’s Color Management
Module (CMM). If color spaces are languages, the CMM is the universal translator. The CMM’s job
is to translate the gamut of one color space into another by matching colors as closely as possible.
Color spaces can also represent device-independent standards called working spaces that are used
while you edit images in Photoshop. Working spaces describe absolute color, referencing Lab color
for best possible accuracy. The working space you choose depends on the type of work you are
doing—whether it is destined for a printer, a printing press, or the Web. Let’s explore color spaces
through another example.
1. Choose Edit Color Settings to open the Color Settings dialog box, as shown in Figure 2.3.

Figure 2.3
Photoshop’s Color Set-
tings dialog box: (left)
the North American
General Purpose de-
faults, and (right) the
U.S. Prepress defaults