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Adobe Photoshop CS2 - Unsharp Mask filter
Article
63 of 100
When
images are reduced in size in Adobe Photoshop the details
tend to blend together and edges get soft therefore requiring
sharpening. The easiest and safest way to deal with this degradation
of the image is to use the Unsharp Mask filter.
Normal sharpening filters
are not designed for photographic images and will sharpen
the image randomly, the Unsharp Mask filter will sharpen only
the areas where one one color area meets another one, sharpening
the edges between those areas.
The Unsharp Mask Filter
has three settings, Amount, Radius and Threshold.
Amount
- smaller, lower resolution images (like images intended for
web viewing) require less sharpening than larger, higher resolution
images (intended for high quality printing).
Radius
- determines how many pixels will be included around the area
that will be sharpened, larger pixels require fewer pixels
and higher resolution, smaller pixels require more pixels.
Threshold
- a 0 Threshold sharpens all the pixels in an images and as
the threshold value goes up the amount of contrast between
pixels becomes greater before they are also considered for
sharpening.
Over
sharpening causes ghosting around an image, as you can see
in the mountain in the image above, which is an image within
an image and has been sharpened too many times.
Below is the same image of the mountain with a more correct
amount of sharpening (although a little bit of ghosting is
still visible at the top of the mountain on the left).
P.S.
Please do not get upset if your personal experience and views
are different from my own. These opinions are mine exclusively
and do not reflect the views or policies of any of the manufacturers
mentioned in these articles ...... George
Mann |
