Well, this seems like a natural thread for this group, so I'll kick it off with this:
Here are two approaches to fixing over-sharpened images in Photoshop. Both rely on the blending mode you are using.
The first is "before the fact" - that is, if you have not sharpened the image yet, do this:
1) duplicate the image, which will place an identical copy above your base layer.
2) do your sharpening on that duplicated layer. If the sharpening produces the dreaded white halo, do this:
3) set the blend mode of that over-sharpened layer to darken;
4) zoom into a problem area and set the opacity to about 66% to start.
5) watching the screen, adjust that percentage as needed.
Using this technique, you may end up with some pixel size darker artifacts, but they will, in the finished print, be basically invisible.
6) you may need to add a gamma adjustment layer to finish it off.
This approach saves considerable time when the halos are many, and spread throughout the image.
If instead you have the halos around mountain or roof-tops, or similar dark vs only slightly less dark areas, or you only have an ill-sharpened image, then you can fix the image without resorting to a new layer.
Using pretty much the same method, do this:
Using the spot tool, create a brush that is soft-edged and 3 or 4 times the size of the halo. There is room for "slop" in this, and since you're going to trace over the halo, you might as well make it easier with a larger brush.
Option click to select the source from the LIGHTER of the two areas (but not the halo itself.) For example a lighter sky with a darker roof-top. Option click the lighter sky.
Then set the blending mode to darken, and simply brush away the halo.
If you have been pixel-peeping to fix halos, either of these techniques will truly make your day.
Tracy Valleau, moderator