Converting between color modes (Photoshop)

When you choose a different color mode for an image, you permanently change the color values in the image. For example, when you convert an RGB image to CMYK mode, RGB color values outside the CMYK gamut (defined by the CMYK working space setting in the Color Settings dialog box) are adjusted to fall within gamut. Consequently, before converting images, it's best to do the following:

• Do as much editing as possible in the image's original mode (usually RGB from most scanners, or CMYK from traditional drum scanners or if imported from a Scitex system).
• Save a backup copy before converting. Be sure to save a copy of your image that includes all layers in order to edit the original version of the image after the conversion.
• Flatten the file before converting it. The interaction of colors between layer blending modes will change when the mode changes.

To convert an image to another mode:

Choose Image > Mode and the mode you want from the submenu. Modes not available for the active image appear dimmed in the menu.

Images are flattened when converted to Multichannel, Bitmap, or Indexed Color mode, because these modes do not support layers.