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Prepping Artwork for Fast Separation

(October 2011) posted on Tue Oct 25, 2011

Rushing the separation process can lead to disaster in production. Find out how to determine which approach represents the best mix of quality and speed for your shop.


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By Thomas Trimingham

A good solution for images that show significant color pollution is to use the layers dialog in Photoshop and then select the main color that you are looking for using the eyedropper tool. You can then adjust this color to the right hue by selecting it from the tool menu and then modifying it in the color-picker dialog. Once you have the proper color for separation from the design, you can use the color-range command in Photoshop on this color to select all of the areas in the image that have this color. Careful use of the fuzziness slider in this dialog box will ensure that you select the right amount of color. Once you create this selection using the color-range tool, switch to the channels menu, and create a new channel by selecting the box at the bottom of this dialog. Fill the selected areas in the new channel with white—assuming you have the new channels in solid black—and then deselect the selection.

The next step is to invert this new channel and then use the curves menu to adjust it so it is very solid black. You can do this by pushing the black point most of the way along the bottom toward the white point in the curves menu. This creates a solid selection area in the channel. The new channel can then be used as a gross selection to create a new layer or adjustment layer in the layers palette. Just control-click (Cmd-click on the Mac) on the channel image in the channel dialog to select the white areas, then invert the selection. Go to the layers menu and, with this selection still active, copy and paste this area into a new layer.



The next step is to use the hue/saturation dialog and average the color in these areas of your new layer by using the colorize command. This new, colorized layer can then be adjusted by opacity or by using a layer-blend mode to merge with the original image underneath. It will force the selected colors into the same family/hue set (Figure 2).


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