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Fixing local under exposure with PS

Thu 31-Jul-03 11:02 PM
This is a method I found useful for solving local underexposure problems and to open up dark areas with PS. I’m not sure about the (image quality) repercussions, so hopefully some of the experts will chip in.

1) Duplicate layer, layer properties “screen”, this will lighten up the entire picture, but more noticeably the dark areas, without loosing contrast. Tweak the layers’ opacity setting until you get a satisfactory adjustment of the darker areas.
2) Copy the green channel, then adjust brightness/contrast so, that the light grays are eliminated and dark grays become (almost) black. This may take some experimenting depending on the picture at hand, and its specific problems.
3) Go back to layers, in the menu bar go to select > load selection > green copy.
4) Hide the selection if necessary (Ctrl H) then eliminate the selection from the layer “background copy”. Adjust opacity if necessary.
5) After flattening the image, I generally apply auto contrast, which compensates for most contrast problems that occur using this method. Sometimes this blows out highlights or over saturates shadows though, which may force you to do a manual brightness/contrast adjustment to get satisfactory results. You might also want to use an ajustment layer which allows you more precise control and undo, in case you don't like the results.

This is a rather crude description of the method, but it works for 80% of my badly balanced or locally underexposed pictures (noticeably the ones where fill-in flash should have been used).
Some experimenting is necessary to get good results, so I suggest trying it out and posting on your experiences.

Very interested in opinions and...

Gerard

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