About color modes

Photoshop Elements provides four color modes: RGB, Bitmap, Grayscale, and Indexed color.

RGB mode RGB is the default mode for new Photoshop images. It uses the RGB color model to assign an intensity value to each pixel ranging from 0 (black) to 255 (white) for each of the RGB components in a color image. For example, a bright red color might have an R value of 246, a G value of 20, and a B value of 50. When the values of all three components are equal, the result is a shade of neutral gray. When the value of all components is 255, the result is pure white; when the value is 0, pure black.

RGB images use three colors, or channels, to reproduce up to 16.7 million colors on-screen. In addition to being the default mode for new Photoshop images, the RGB model is used by computer monitors to display colors.

Bitmap mode This mode uses one of two color values (black or white) to represent the pixels in an image. Images in Bitmap mode are called bitmapped 1-bit images because they have a bit depth of 1.

Grayscale mode This mode uses up to 256 shades of gray. Every pixel of a grayscale image has a brightness value ranging from 0 (black) to 255 (white). Grayscale values can also be measured as percentages of black ink coverage (0% is equal to white, 100% to black). Images produced using black-and-white or grayscale scanners typically are displayed in Grayscale mode.

Indexed Color mode This mode uses at most 256 colors. When converting to indexed color, Photoshop Elements builds a color lookup table (CLUT), which stores and indexes the colors in the image. If a color in the original image does not appear in the table, the program chooses the closest one or simulates the color using available colors.

By limiting the palette of colors, indexed color can reduce file size while maintaining visual quality--for example, for a Web page. Limited editing is available in this mode. For extensive editing you should convert temporarily to RGB mode. (See Converting to indexed color.)

Working with Color > Choosing a color mode > About color modes