Adobe PHOTOSHOP ELEMENTS 2 User Manual page 188

CHAPTER 10
180
Applying Filters, Effects, and Layer Styles
Sharpen Edges and Unsharp Mask
in the image where significant color changes occur
and sharpen them. The Sharpen Edges filter
sharpens only edges while preserving the overall
smoothness of the image. Use this filter to sharpen
edges without specifying an amount. For profes-
sional color correction, use the Unsharp Mask
filter to adjust the contrast of edge detail and
produce a lighter and darker line on each side of
the edge. This process emphasizes the edge to
create the illusion of a sharper image. (See "Using
the Unsharp Mask filter to sharpen photos" on
page 180.)
Using the Unsharp Mask filter to sharpen
photos
Unsharp masking, or USM, is a traditional film
technique used to sharpen edges in an image. The
Unsharp Mask filter corrects blurring introduced
during photographing, scanning, resampling, or
printing. It is useful for images intended for both
print and online viewing.
Unsharp Mask locates pixels that differ from
surrounding pixels by the threshold you specify
and increases the pixels' contrast by the amount
you specify. In addition, you specify the radius of
the region to which each pixel is compared. The
effects of the Unsharp Mask filter are far more
pronounced on-screen than in high-resolution
printed output. If your final destination is printed
output, experiment to determine what settings
work best for your image.
For information on other filters for sharpening
images, see "Sharpen filters" on page 179.
Find the areas
To use Unsharp Mask to sharpen an image:
Choose Filter > Sharpen > Unsharp Mask, and
1
select the Preview option.
Click the preview window in the Unsharp Mask
dialog box window to see how the image looks
without sharpening. Drag in the preview window to
see different parts of the image, and click + or – to
zoom in or out.
2 Do one of the following:
Drag the Amount slider or enter a value to
•
determine how much to increase the contrast of
pixels. For high-resolution printed images, an
amount between 150% and 200% is usually
recommended.
• Drag the Radius slider or enter a value to
determine the number of pixels to sharpen
around edges. For high-resolution images, a
radius between 1 and 2 is usually recom-
mended. A lower value sharpens only the edge
pixels, whereas a higher value sharpens a wider
band of pixels. This effect is much less
noticeable in print than on-screen, because a 2-
pixel radius represents a smaller area in a high-
resolution printed image.
Drag the Threshold slider or enter a value to
•
determine how different pixels must be from
the surrounding area before they are considered
edge pixels and sharpened. To avoid intro-
ducing noise (in images with flesh tones, for
example), experiment with Threshold values
between 2 and 20. The default Threshold value
(0) sharpens all pixels in the image.
Click OK.
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