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Brie Dodson <[log in to unmask]>
Reply To:
SciArt-L Discussion List-for Natural Science Illustration- <[log in to unmask]>
Tue, 21 Sep 1999 10:53:00 -0400
text/plain (55 lines)
Hello, everyone and especially Frank! I've been away from the
list for a year or more, and it's good to see so many familiar
names again.

A few days ago there were a couple of posts on retouching
photographs in Photoshop. Here's a technique I discovered when I
needed to clean up a scan of a badly damaged slide.

1) Save the scan as a Photoshop file. Without taking into account
the damaged areas, make overall corrections (such as unsharp
mask, Curves and Hue-Sat) to the background layer and then
duplicate it. The new layer will come in on top of the old one.

2) On the new layer, use Filter - Noise - Dust & Scratches (or
another filter, as you prefer) to get rid of as much damage as
possible. Be liberal and ignore the bad effect on the rest of the

3) Apply a layer mask and select Hide All.

4) The new layer will show through the layer mask. (Since you
selected Hide All, none of the new layer will be visible yet, but
that will change.) Working on the new layer, select white as the
foreground color and select the airbrush tool. Use something like
50 percent pressure, and select the check box to make the tool

5) Using the smallest brush size practical, airbrush out the
scratches and other damage. Work precisely - i.e., for a scratch,
follow closely within and along the scratch. Cover the edges of
the scratch, but don't intrude too far into the undamaged areas.
What you are doing is revealing the corrected version of the scan
in damaged areas. But in clean areas, the original scan (with its
sharper picture quality, which has not been degraded by the Dust
and Scratches filter) still shows through.

6) When you are finished, select Layer - Remove Layer Mask and
opt to apply the layer mask before removing.

7) Select Layer - Merge Down. This merges the airbrushed
corrections down onto the original scan. Because you used only
partial pressure on the airbrush, the edges of the corrections
will be as un-noticeable as possible.

Voila! The photo is reasonably well repaired and the quality of
the clean parts has been preserved. This is quicker than spending
hours trying to clone out damage manually, and gives better
overall results than applying a filter to the entire image.

Brie Dodson (formerly Brie Combs)
9712 Ashby Road
Fairfax, VA 22031
(703) 597-7163
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