Adobe 13101332 User Guide - Page 91

Adobe Photoshop Help Using Help | Contents | Index Working with Color Back 91 Color gamuts (Photoshop) A gamut is the range of colors that a color system can display or print. The spectrum of colors seen by the human eye is wider than the gamut available in any color model. Among the color models used in Photoshop, L*a*b has the largest gamut, encompassing all colors in the RGB and CMYK gamuts. Typically, RGB gamuts contain the subset of these colors that can be viewed on a computer or television monitor (which emits red, green, and blue light). Therefore, some colors, such as pure cyan or pure yellow, can't be displayed accurately on a monitor. CMYK gamuts are smaller, consisting only of colors that can be printed using process-color inks. When colors that cannot be printed are displayed on-screen, they are referred to as out-of-gamut colors-that is, outside a CMYK gamut. (See "Identifying out-of-gamut colors (Photoshop)" on page 136.) Important: The gamut for an RGB or CMYK image depends on its document profile. (See "About color management" on page 102.) A B C Color gamuts: A. A Lab color gamut B. An RGB color gamut C. A CMYK color gamut Adjusting the monitor display Although the RGB color model used by computer monitors is capable of displaying much of the visible spectrum, the video system sending data to a given monitor often limits how many colors can be displayed at once. By understanding how color data is measured in digital files and on-screen, you can better adjust color display settings to offset the limitations of your video system. Specifying 8-bit color display (Photoshop) When you're working with a display system that supports 8-bit color, the monitor displays only 256 different colors at a time. As a result, Adobe Photoshop uses a technique called dithering to mix pixels of available colors and thus simulate colors not currently available. Note: Most monitors are capable of displaying 24-bit color. To achieve the best results, avoid using 8-bit display mode when editing color images. By default, Adobe Photoshop uses pattern dithering, which can result in a distinctive pattern of darker or lighter areas in the image. In contrast, diffusion dithering eliminates this distinctive patterning by using the surrounding pixels in the mix of pixel color. But diffusion dithering can cause visual inconsistencies when only part of a screen is redrawn as you scroll, edit, or paint. Keep in mind that dithering effects only appear on-screen, not in print. Using Help | Contents | Index Back 91