Brandon,
It's a misconception that CMYK or RGB color gamuts are inherently larger or smaller than one another simply by being CMYK or RGB. It's true that many RGB device gamuts are larger than many CMYK device gamuts, but that's because by nature most RGB devices tend to be transmissive and most CMYK devices tend to be reflective. It's the transmissive vs. reflective rendition of color that accounts for the larger RGB gamuts. Since--regardless of how you profile your printer--it's still going to print with CMYK primaries and still going to print reflective images, even if you could create an RGB profile for it, assuming all else being equal, the profile would have no larger of a gamut than a CMYK profile of the same device.
What CMYK and RGB refer to in the instance in which you're using them is strictly the print stream as sent to the printer. And no, if you're driving the printer with a RIP, you cannot profile it as an RGB device. The reason is that the RIP creates a CMYK print stream. That's its function in life. Somehow or another, when sending data to any device that prints with primaries, there is information that must be generated that tells the primaries how to make the printing dots. If you use a RIP, the RIP creates that information and sends it to the printer as a CMYK print stream. If you don't use a RIP, then that information still has to be generated, but it's generated by the printer internally, and the print stream to the printer is referred to as an RGB print stream.
That's why RIP-driven printers use CMYK profiles and non-RIP-driven printers use RGB profiles.
But the profiles themselves characterize the same printer printing with the same primaries at the same resolution on the same media. Any differences between them will be created simply by how well whoever made them set up the conditions under which they were made.
Mike Adams
Correct Color
