Setting the color depth

Color depth is the number of colors in the graphic. You can make your files smaller by reducing the number of colors they use. Reducing color depth discards some colors in the image, beginning with those used least. Pixels containing discarded colors convert to the closest color remaining in the palette. This can reduce the quality of the image.

To select a color depth:

• Select an option from the Colors pop-up menu in the Optimize panel or type a value in the text box. You can select from 2 to 256 colors.

  NOTE

  The actual colors in the image could be lower than the maximum number of colors you select. The number at the bottom of the color table indicates the actual number of colors visible in the image. If no number is visible, you'll see a Rebuild button, which indicates you should rebuild the color palette. For more information, see Viewing colors in a palette.

To select a color depth beyond 256 colors:

• Select a 24- or 32-bit file format from the Export File Format pop-up menu in the Optimize panel.

  NOTE

  Higher color depths create larger files and are typically not ideal for web graphics. Use only 24- or 32-bit color depths when exporting or saving photographic images with continuous tones or complex gradient blends of colors. For high-color-depth graphics on the web, use JPEG files. For more information, see Optimizing JPEGs.