I can appreciate that someor more than somepeople work with an RGB workflow, and I think that in a close, tightly controlled environment this is entirely feasible, as ICC profiles can be implemented and everyone knows and understands what is going on. That's assuming everyone's computer monitor has been properly calibrated. Everyone has and uses the same correct ICC profiles and knows the proper procedure for the workflow. Every single film house I have worked in works primarily with CMYK files for a couple of reasons.
The first reason is that files come in from many different sources. Many, if not just about all, of the clients have no idea if the profile attached to a file is correct, should be left on, turned off, or discarded. Most clients don't even know what an ICC profile is. Clients will supply a whole range of images. The client may have converted the images incorrectly, or a profile may be attached to the file because "that's what we always use." There is a mass amount of confusion out there. I think that basically most people simply don't understand the conversion process between color modes, and don't understand the ramifications of what they do.
The use of images is basically for a few different print media applications. Magazines would be at the top of the food chain, as they are typically of the best quality. From the magazine image, various images are generated as needed: newspaper, billboard, or large format.
In any of these cases, it generally appears that the preferred method is to convert the image to CMYK. This is done so that the customer gets no false hopes as to how the final image will look on paper. Let's face it: an RGB file looks great on screen, and on some printer outputs like an Epson, the print looks down right gorgeous. The reality is that the CMYK color space is far smaller than RGB, and many colors are limited in the color range compared with RGB, as I am sure you know. It is preferred for the print medium that the images are proofed in CMYK and shown to a client in that way. I have personally had problems when a photographer supplied the agency with an RGB image he made from his Epson, and the file came in to be retouched and properly proofed on a high-end device that simulates the look of the actual print medium or printing press only to have the client wonder what happened to the color that was on the photographers proof! Try and match the photographer's proof: it isn't going to happen. It's even tougher to explain why.
Files should be kept RGB if that is requested, or if they are to be printed on an RGB device. Some of the large format printers will print to backlit film-based material, and in a case like that, RGB makes sense. I know that the push has been on for an RGB workflow all controlled with ICC profiles, but I have yet to see it happen in the real world. Maybe you have another view on this; I'd be interested to know. I think there is an argument for either an RGB workflow or a CMYK one, but the reality is that anything put on paper or print will eventually be made up of typically four colors, CMYK, and in the professional film houses I have been in, the workflow has been CMYK. With photographers shooting digital, the images coming from their cameras are RGB, which is great, and by all means supply the images to me or a film house as RGB. However, I would leave the converting to CMYK to someone who really understands the process. If an image is not going to be displayed on an RGB device like a TV or a movie to keep all of the brilliant RGB color, and it is intended for a print medium, and one has done a very good job of converting the original file from RGB to CMYK (or at least as good as it is going to get), then what reason would you want to keep the file as RGB if the intended use is a print medium? This would mean that you would go back to the original RGB file every time to make a change to the file, only to have to reconvert each time to CMYK. In a large shop, this could be a problem, as Joe Blow may convert it differently than someone else another day. This is a reality in a large film house, studio, or agency. Again, if everyone knew what was going on, maybe this would be feasible.updated