Gray and Black (CMYK and RGB)

When the Gray (RGB) option is turned on, any RGB color that has equal R, G, and B values is printed as K-only black instead of CMYK black. Similarly, when Gray (CMYK) is turned on, any CMYK color where C, M, and Y are 0 (zero), and K is any value is printed as K-only black instead of CMYK black.

You can turn on Gray (RGB) or Gray (CMYK) for either Text and Graphics or Text, Graphics, and Images. "Graphics" refers to vector graphics. "Images" refers to bitmap images.

The following limitations apply:

The Gray (RGB) and Gray (CMYK) options have no effect on a job that is sent as separations.
If CMYK Processing Method is set to Pure Primaries, Gray (CMYK) does not affect the output.
If CMYK Processing Method is set to Quick, Gray (CMYK) does not affect the output.
If Separate RGB/Lab to CMYK Source is turned on, Gray (RGB) is turned off. Likewise, if Gray (RGB) is turned on, you cannot turn on Separate RGB/Lab to CMYK Source.
If Black Text and Graphics is set to Pure Black On or Rich Black On, it takes precedence over Gray (RGB) and Gray (CMYK) for 100% black text and graphics.
If a gray is specified as a spot color, Gray (RGB) and Gray (CMYK) do not affect that gray.