Color separation in Photoshop

How it is actually done

The route is much the same everywhere, and it is not one button.

• Picking colours. Color Range or an eyedropper over the artwork to lift the area each ink covers.
• Channels. Each ink becomes a channel, by hand, with the edges cleaned up afterwards.
• Underbase. Merging the channels into one, choking it, removing what should not sit on it.
• Trapping. Spreading neighbouring inks where registration will not hold the seam.
• Halftone. Bitmap mode with Halftone Screen, one channel at a time, or output through a RIP.
• Checking. By eye. Thin lines and small dots are found by zooming in and looking.

None of this is hard on its own. The difficulty is that the steps are many and sequential, and a mistake at the second one only shows at the sixth.

The time goes on the second separation, not the first

The first job is interesting. Then comes the part nobody enjoys: the next order opens from nothing, because none of what was decided last time was written down anywhere.

Line count, angles, print order, how far the base was choked, what counted as the minimum line. All of it lives in one operator’s head, so the same artwork separated by two people, or by the same person six months apart, gives two different runs. That costs more than the hours do.

Where Photoshop cannot be replaced

Drawing, retouching, rescuing a bad source file, setting type, cutting a subject out of its background. Everything that needs an eye and a hand stays where it was.

This is not a competition. An editor and production preparation do different jobs, and no separation tool is going to draw for you.

What an automated pass gives instead

The same work, the same way every time, with a list of what the press will not hold.

• Sameness. The same file with the same profile gives the same plates a year later.
• Checks. Thin strokes, closing gaps and undersized dots are found by measurement rather than by eye.
• A report. Line count, angles, print order and profile sit in a file rather than in memory.
• Finished films. TIFF per ink, layered PSD and PDF, a preview and an ink map in one archive.

A sensible division of labour

Fix the artwork where you are good at it. Separate and output where the work repeats.

The layered PSD in the archive opens in Photoshop, so if something wants a hand after the automatic pass, nothing is stopping you. The difference is that you are adjusting details rather than building the whole thing from nothing.

FAQ