Making a Gray Scale Step Wedge

You can create gray step scales by filling a document (or a marqueed selection area within a document) with a black to white gradient, then use Image, Adjust, Posterize to give it the desired number of gray steps. If you choose 11 Levels in the Posterize dialog box, you get gray steps in even 10% increments from 0% to 100%. If you choose 21 Posterize Levels, then you get gray values in finer 5% increments.

This is useful when testing a printer to see if either highlight or shadow tones are crushed together, or to see if a printer can hold a very light gray color. It is also useful to view on your monitor to determine if it needs calibration. You should be able to view all the tones from black to white on a properly calibrated monitor.

This example shows an illustration containing a step wedge at the bottom. It was used to check print tones for reproduction purposes. The step wedge was made by drawing a long, skinny rectangular marquee at the bottom of the document, filling it with a black to white gradient, and then posterizing to 21 levels. This gave 5% increments to check the extremes of the print tones, and to check if printing problems were caused by the toning of the photos, or if other problems affected reproduction. Small hash marks were manually created at the borders of adjacent gray steps to identify them in case the printer crushed a range of tones together.

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