Photoshop® CS3 Channels and Masks Bible

Chapter 11. Working with Lab Color

IN THIS CHAPTER

• Understanding Lab Color

• Sharpening images with Lab Color

• Making colors pop

• Adding noise to Lab Color images

• Reducing noise

• Black and white to color in Lab

An image's color mode ultimately affects its appearance. In Photoshop, you can choose a specific color system or mode that organizes the color information. RGB Color Color, CMYK Color, Lab Color, and Grayscale are common choices and are used to achieve specific output results. Each mode has a system of color channels with specific characteristics. An image that has been converted to Lab Color is unique in that it provides access to color information that is unavailable in the other modes.

You may have avoided this color system simply because it seems mysterious with its three channels, cryptically named with letters and its peculiar system of positive and negative numbers. In this chapter, I attempt to demystify Photoshop's most powerful color mode.

Understanding Lab Color

Lab Color is device independent—sort of. It is independent of the kind of information that peripheral devices, such as monitors, scanners, and digital cameras use to describe color. But in fact, it is directly related to the most perfect optical device of all — the human eye. Lab Color is used to describe the complete range of colors that humans can see.

The three color channels in Lab images divide the information into an L channel, which contains brightness information and two color channels — a and b (see Figure 11.1 ...