Exporting CMYK and spot colour separations in Paint by Zaweba

A printed colour picture is really several single-colour pictures laid on top of each other, one for each ink. Those single-ink images are called separations, or plates. Paint by Zaweba makes them with File > Export > Separations, which writes the C, M, Y, K and spot plates as PNG or TIFF files, or as one PDF with labels and registration marks, with optional halftone screens.

Why you might need them

Most print shops make their own plates from your PDF or TIFF, so plenty of people never need to export separations themselves. The times you do are usually hands-on. Screen printers burn a separate screen for each colour and need a film or image for each one. Risograph and other small-run duplicators print one colour at a time from separate masters. Students learning print production want to see how a picture splits into inks. And designers checking a tricky file sometimes want to inspect each plate before sending it out.

What gets written

Each plate is a greyscale image showing where and how much of that ink will be laid down. Darker means more ink. The C, M, Y and K plates come from the document's colour values, and any spot colours get plates of their own.

Because a CMYK document in Paint by Zaweba keeps true CMYK values on each pixel layer, the separations use those values rather than converting from RGB at export time. That means the numbers a prepress operator set are the numbers on the plates.

You can write the plates as individual PNG or TIFF files, which suits workflows where each plate is printed or processed separately, or as one PDF. The PDF version labels each plate and adds registration marks, the small targets that let a printer line up the colours exactly.

Halftone screens

Presses and many duplicators can't print true shades of grey; they print dots of solid ink. A halftone screen turns tone into dots of varying size. Paint by Zaweba can apply halftone screens when exporting separations, so the plates are ready for processes that need them, such as screen printing with film positives. If your printer will screen the plates themselves, leave the option off and send continuous tone.

Getting good plates

Start from a properly prepared CMYK document. Convert from RGB using the right press profile, check the result with Proof Colours and the gamut warning, and fix problem areas before separating. Look at each plate with View > Proof Setup set to a single plate if you want to preview it before export.

Mind the total ink. Very dark areas built from heavy amounts of all four inks can cause drying problems. Your printer will tell you their limit.

Add trapping where solid colours meet if the process needs it. Image > Trap spreads lighter inks under darker ones, which hides small misregistration on press.

Label clearly. If you export files rather than the PDF, name them so nobody confuses the magenta plate with the black one.

The end of the print chain

Separations are the last step of a print chain that Paint by Zaweba covers from end to end: colour settings, CMYK documents, soft proofing, trapping and finally the plates. For a small studio or a hobby print maker, having that whole chain in one free, offline app is a real convenience.