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The
final step, just before printing, is sharp processing with an “Unsharp mask” filter.
Performing sharp processing makes outlines more conspicuous, and the image appears sharper. Although “Sharpen” is
emphasized by strengthening the contrast difference of adjoining pixels, an ”Unsharp
mask” filter uses three parameters. They are "amount," which specifies the
strength of the sharpness itself, "radius," which specifies the range of strength
of the contrast difference, and "threshold," which specifies the level where sharp
processing starts. Parameters are used to change the setup according to the print resolution
and the image.
Here, try using the ”Unsharp mask” filter on two images, a casual portrait, and a landscape, before printing
on an ordinary printer with a resolution of 300 dpi. |
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| Here, try using the {qnsharp mask・filter
on two images, a casual portrait, and a landscape, before printing on an ordinary printer with a
resolution of 300 dpi. |
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With an image of a person?s face, outlines, such as eyes,
nose, and mouth generally should be sharpened. However, if the skin is also sharpened, it may look
like dry, rough skin. To avoid this look, the threshold value is heightened slightly to weaken the
sharpening somewhat. |
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This is the portrait before any
sharpening. Use the {qnsharp mask・filter to sharpen the eyes, nose, and mouth. At the same time,
we must be careful not to roughen the subject?s skin. |
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Open the {qnsharp mask・filter
to start the sharpening process. Use two different sets of parameters and compare the results. |
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Using the ?Unsharp mask・filter
with the parameters set to Amount = 180, Radius = 1.5, and Threshold = 8 produces these results.
The face is crisper, and the skin texture is still soft. |
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Using the ?Unsharp mask・filter
with the parameters set to Amount = 180, Radius = 1.5, and Threshold = 0 produces these results.
Only the threshold parameter is different from the previous example, but using the low threshold
level causes sharpening to occur even on very small contrast changes, causing the skin to appear
rough and dry. |
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With images of scenery, most
objects are often far away. Consequently, trees, buildings, etc. are quite small, making a boring
image, which lacks detail. To bring out the detail clearly, sharpening with an {qnsharp mask・filter
is indispensable. Here again, we will make two examples, one of good use of the filter and one of
poor use. |
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This is the image before any
sharpening. The grass in the background has no detail. Use the {qnsharp mask・filter to sharpen it
as well as the goat?s fleece. |
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Open the {qnsharp mask・filter
to start the sharpening process. Use two different sets of parameters changing only ?radius・and
compare the results. |
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Using the ?Unsharp mask・filter
with the parameters set to Amount = 200, Radius = 1, and Threshold = 2 produces these results. The
grass and the goat?s coat are crisper, and the goat?s image is sharper overall. |
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Using the ?Unsharp mask・filter
with the parameters set to Amount = 200, Radius = 4, and Threshold = 2 produces these results. Only
the radius parameter was changed--- from 1 to 4. Since the radius of the sharpening is larger, the
outline is ruined and the color has bled. The image is poor. |
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![These supplementary functions are used during retouching.]](../../images/reference/function/menu_photo_e.jpg)
