Terry Relph-Knight

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Posted on 26-03-2009

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Hard Copy Colour Proofing

In theory the ideal colour proof work flow is to print proofs on the printer that will be used for production runs. In the case of commercial press printing this is impractical because the presses involved are not designed to print just the few pages required for colour proofing. In the past hard copy press print proofs were produced using a (DuPont) Chromalin, (Kodak) Matchprint or similar proofing system. Unfortunately the word ‘Chromalin’ is often used like the word ‘Hoover’ is used as a generic term for vacuum cleaners and if you ask a printer for a Chromalin proof that may not literally be what you get.

By the time pages reach the printing press the edited page layouts have been split into the component C, M, Y and K (known as ‘separations’) used to print the finished pages. To make a Chromalin proof, the separations, either in digital file form, or as page spread size photographic negatives are used to produce positive colour exposures of the four colours on four sheets of plastic. These sheets are then aligned and bonded together to form the final colour proof. Other photographic proofing systems use the separation negatives to produce a colour photographic print on photo print paper. The digital files or negatives used to make the proof are also used to make the printing plates for the press, so in principle there is an exact correspondence between the proof and the press print.

The problem with all these colour press proofing systems is that they do not use the inks and paper that will be used in the final print run. They will show errors such as registration problems or obvious colour errors introduced at the separation stage, but will not necessarily produce exactly the same colour appearance as the final printed output. This is particularly obvious with proofs printed onto photographic paper, as the white of the photo print paper normally won’t be the same as the white of the paper used in the press.

Hard copy colour proofs are relatively expensive and time consuming to produce, commercial press operators or print service bureaus apply a charge for each colour proof (in the UK, £45 to 50 each for A4 proofs). So publications will normally only request hard copy colour proofs for images of particular importance.