Paper Separations

With CMYK process printing, the illusion of continuous color is created by printing tiny dots of four standardized inks: Cyan, Magenta, Yellow, and blacK.  When printing with one or more "spot" colors, individual premixed inks are laid down one by one.  No matter what technique is used, it's necessary to divide up the job into component colors, a technique known as "color separation."  Ultimately, one "film separation" will be output for each ink to be printed.

Film separations are made from your files by printing black emulsion on clear acetate.  Paper separations are made in exactly the same way, except that they are printed with laser toner or inkjet ink on plain paper.  "Paper seps" enable you to check your work before placing the actual film order - reconciling color names, examining overprinting and knockout issues, detecting black mismatches, finding missing and corrupt fonts, tracking down mysteriously vanishing elements, etc.  If you do all that work in advance, it means that all the imagesetter operator has to do is match the proofs that you send along with your files.

Paper seps are the mark of the technically proficient designer.  If someone has gone to the trouble of providing seps, it demonstrates that they are taking responsibility for where ink goes down, rather than relying on someone else to make their job look the way that it's supposed to.  It shows that they understand the limitations of designing on the desktop, looking at low resolution composite images of dubious color accuracy on an RGB monitor.  It's also indicative of a certain investment level for the designer's workstation, since a Postscript-enabled printer is necessary for outputting separations.

Nothing will teach you more about printing than trying to troubleshoot separations.  Nothing will cause you more frustration, or spare the production people downstream more frustration.  Nothing will save you more money.  Nothing will give you more control over the finished product.

Supplying Paper Separations

There should be one hard copy paper sep for each piece of film to be output.  Printouts should be full size, tiled if necessary.  Although the film for the paper products will be output negative, it is perfectly acceptable to provide positive proofs, since doing so usually saves a lot of ink.  If you must provide miniaturized seps, the scaling percentage should be indicated; however, we discourage scaled paper seps since it is impossible to mate them up with the film precisely (which makes proofing the film against the paper seps much more difficult), and miniaturization may obliterate important details.