Adobe Photoshop CS3 User Manual
Page 218
PHOTOSHOP CS3
User Guide
211
Selecting a channel with the greatest contrast
•
Duplicate the selected channel.
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With the duplicate channel selected, choose Filter > Stylize > Find Edges.
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Choose Image > Adjustments > Invert to invert the image.
Find Edges filter applied and image inverted
•
With the inverted image still selected, choose Filter > Other > Maximum. Set the radius to a low number and
click OK to thicken the edges and randomize the pixels.
•
Choose Filter > Noise > Median. Set the radius to a low number and click OK. This averages the neighboring
pixels.
•
Choose Image > Adjustment > Levels and set the black point high to get rid of random pixels. If necessary, you
can also paint with black to retouch the final edge mask.
Setting the black point high in Levels to eliminate random pixels in the edge mask
•
Choose Filter > Blur > Gaussian Blur to feather the edges.
Important: The Maximum, the Median, and the Gaussian Blur filters soften the edge mask so that the sharpening effects
blend better in the final image. Although all three filters are used in this procedure, you can experiment using only one
or two.
2
In the Channels palette, Ctrl-click (Windows) or Command-click (Mac OS) the duplicate channel to make the
edge mask a selection.
3
In the Layers palette, select the image layer. Make sure the selection is still visible on the image.