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Working with Colors

When you work with Photoshop, it lets you view and adjust your colors in all sorts of different ways. It's difficult to adjust saturation in an image, for example, by manipulating RGB or CMYK values directly, so Photoshop provides tools that let you apply changes in hue, saturation, and brightness to the underlying RGB or CMYK data. Likewise, if you have an RGB image but you plan to print it in CMYK, you can use Photoshop's Info palette to keep track of what's happening to the CMYK values you'll eventually get when you do the mode change from RGB to CMYK.

We do face two fairly large problems, however. The first is that every time we do a mode change, we lose some image information, because our images only have 256 shades of each color, and as we convert from one color space to another, some of these get lost due to rounding errors. Photoshop lets us work around this by providing information about what we'll get after we've done the color-space conversion, without our actually having to do so until we've perfected our images. We discuss this in much more detail in Chapter 7, Color Correction.

The second problem is that the color spaces in which most of our images are stored, RGB and CMYK, are device dependent—the color we'll get varies depending on the device we send it to. Worse, each device has a range of colors it can reproduce—called the color gamut—and some devices have a much wider gamut than others (see Figure 4-4 on page 114). For example, color film can record a wider range of colors than a color monitor can display, and the monitor displays a wider range of colors than we can reproduce with ink on paper; so no matter what we do, some of the colors captured on film simply can't be reproduced in print.

Fortunately, Photoshop has tools that let us remove some (if not all) of the variability from our RGB and CMYK color definitions, and it lets us specify the gamut of our monitor and our CMYK output devices. The next chapter, Color Settings, is devoted to explaining what those tools are, how they work, and how to use them.

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