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Unsharp masking is considered standard practice for sharpening a
soft image. It exaggerates the edge contrast of details, but can also
inappropriately exaggerate textures, faults, and other artifacts.
The High Pass filter offers a more controllable alternative.
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Download the mousegirl.zip archive, extract the mousegirl.jpg file, open it and save it as
a Photoshop document. Create a duplicate
of the background layer by pressing
Command/Ctrl-J, then name the new
layer High Pass. Set the blending mode
of the High Pass layer to Overlay, which
temporarily increases the overall contrast
of the image.
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Select Filter > Other > High Pass and
arrange the filter dialog box so you can
clearly see it alongside your image; make
sure the Preview option is checked, too.
Now concentrate on one critical area,
such as the girl’s face, and reduce Radius
to 0.1 pixels. Slowly drag the Radius slider
toward the right and keep an eye on the
image as it begins to sharpen. Zoom in
and out by pressing Command/Ctrl-+
and Command/Ctrl-–. To maneuver
inside the preview, click-drag while
pressing Space. The High Pass dialog box
preview only shows details that will be
sharpened, a significant advantage over
Unsharp Mask. Inspecting this allows
you to avoid undesirable texture exaggeration
in smooth areas like skin. Once
you’ve found the optimal Radius, in this
instance 10 pixels, click OK.
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When you toggle the High Pass layer’s
visibility you can see that the girl’s face
looks appropriately sharpened, but her
hat has been oversharpened. Add a mask
and select the mask thumbnail. Hide the
oversharpening by painting over the hat
and background area with a soft black
brush. Restore any accidentally removed
sharpness, such as the mouse’s fur, by
painting over it with a soft white brush.
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At this point, her shirt could use a bit
more sharpening, so duplicate the High
Pass layer. But this makes everything too
sharp! Fix this by selecting the layer mask
thumbnail and painting over everything
but her shirt with a soft black brush. Even
now her shirt is still a bit too sharp, so
finish off by lowering the layer’s Opacity.
Compare your final version to the unsharpened
original by Option/Alt-clicking
on the background layer’s visibility icon. The original image is shown at left, with the final one below.
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Sharpening Tips
- Determine the amount of sharpening
by your print size and viewing distance.
- The smaller the final output and the
closer it will be viewed, the less sharpening
the image will tolerate. An image
may need several sharpening passes.
- Highly textured areas such as foliage
need the least sharpening, while faces
need the most.
- Watch for halos. These pale outlines
that trace around details are tell-tale
evidence of oversharpening.
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Doug Nelson is a freelance writer,
technical editor, and founder of
RetouchPRO.com, an online community
for photo retouchers.
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