The separation of RGB-images is in very most cases done by an ICC-profile. In a standardized print production, the ICC-profile should be based on the characterization-data compliant to the specification, printing process and paper type.
In most cases there are different sources for profiles based on standard-characterization-data. Well known are the profiles shipped with the Adpbe Creative Suite, which are also available by download from the Adobe website, the profiles from ECI based on FOGRA characterization-data and the profiles from SWOP and GRACoL.
The advantages of GCR based profiles for PSO/FOGRA, SWOP, GRACoL
A new source is www.colormanagement.org which offers profiles for all relevant standards (PSO/FOGRA, SWOP, GRACoL, IFRA) with different separation settings. Currently this is the only source of free available profiles with a strong GCR for a more stable print production. Near neutral colors are hard to control and match in offset printing. Using profiles with a stron GCR will lead to perfect neutrals in the print run and a much better overal gray balance. For best possible quality, the printing house should have calibrated their CtP according ISO 12647-2 / PSO in Europe or G7 in the US.
Please notice alo, that the GCR profiles at www.colormanagement.org use a very strong GCR in the neutral and a medium GCR in the more saturated colors like e.g. Skin tones.
Print buyer, agencies / prepress or printers who are sceptical about GCR should make the following test:
choose some RGB pictures including neutrals and skintons
- separate the pictures with a normal and a GCR profile based on standard printing conditions and put them in a layout page
- make proof of the layout in the correct printing condition
- make an offset print with the printer matching the proof
If the printing press is in normal state, it will be much easer for the printer to match the GCR based separation instead the standard separation.