RGB Prints, CMYK Proofs and Setting Realistic Expectations

There are two kinds of proofs/prints: one that matches the high-gamut RGB file and one that matches the actual final printing process. Both are correct and both serve a purpose. For example, as a photographer you want to prove you accurately captured the scene and an RGB print is a reference for the shot. An RGB print is just that, a depiction of the shot. It is looking backwards at the process and the photography. In some way it is a proof, proof that you did your job correctly.

If you are supplying proofs/prints to your clients it is important that you are setting realistic expectations. If you supply an RGB print on a bright blue-white photo paper then you cannot call it a press proof. It is an image proof, an RGB Proof. Again, it is a high gamut representation of the shot, not the final press.

Anyone along the supply chain can offer a proof of the final process but you need to know how the job is being printed. Is it digital, magazine (SWOP), signage, flexo, newsprint (SNAP) or sheetfed (GRACoL). Each requires a specific colour setup.

In the printing industry we have three main categories in which we divide the various printing variables. Starting with the highest quality and working our way down we have GRACoL, then SWOP and finally SNAP. This is the first of many acronyms. If you want a smile say it in the order of SNAP, GRACoL, SWOP… think cereal.

GRACoL stands for the General Requirements for Applications in Commercial Offset Lithography. The GRACoL specification pertains to sheetfed offset printing using ISO defined inks and paper (#1 or #2) and is generally for short run, high quality printing.

SWOP stands for Specifications for Web Offset Publications. SWOP is a colour reproduction specification for web offset lithography. The SWOP specification pertains to web offset printing using ISO defined inks and paper. There are two SWOP specifications, SWOP3, for printing on a #3 sheet stock and SWOP5 for printing on a #5 sheet stock. This is most often magazine publications.

SNAP stands for Specifications for Newsprint Advertising Production. The specifications pertain to proofing and coldset printing by offset lithography on webs of newsprint grade paper (e.g., newspapers, pre-printed advertising inserts, and other printed materials). This is strictly a newspaper specification.

Your options when creating a print/proof are:

1. Printing via the supplied driver on a photo paper. This is an RGB process and often referred to as an RGB Print.

2. Printing via a software RIP using various proofing papers. This is a CMYK process and referred to as a CMYK Proof.

The first option, when combined with the right profiles and calibration can yield a very accurate print, but it will not match the final image when it is printed on a press. However there is a workaround to make an RGB print look a lot more like and CMYK Proof. To learn more go to the GAM website and enter in the search field: RGB Proofing and matching to a CMYK proof.

The second is obviously a more expensive option, as you need to purchase an extra piece of software (RIP) and proofing media. It may require a custom calibration and set up. It also requires that you know how the file is being printed.

Another area that is often misunderstood is the paper used in proofing. If the paper has the word ‘photo’ in the name, then there is a good chance it should not be used for proofing. Most photo papers have a bluish tint in the white, this blue white base is not obvious at first but when you compare it to the paper used in the magazine, you will see a big disconnect. Alternatively, if the media has the word proofing in it then it has been targeted to the white point of the paper on press.

If you compared two proofs, one made on Epson Premium Luster and the other on Epson Standard proofing paper you could see as much as 20% difference between the two, all due to the paper colour. Try to think of the paper colour as the 5th colour in CMYK printing. Many images, especially high key images, rely on the paper white to fill the areas containing few to no dots. As a result, these colours are largely determined by the paper colour. If you have a blue-white paper then there is no colour management that can fix it.

To recap, if you are supplying an RGB print, tell your client it is a print not a proof. If you are creating proofs, check with the printer to ensure you are targeting the press specification correctly. Check what media you are using and avoid photo papers for proofing.

Angus Pady