Single-Star Halo Reduction

Occasionally you'll have a really bright star in an image that's so bloated it detracts from your target. Here's a way to get it down to size.

  1. Open your image
  2. Use the Elliptical Marquee tool to select a round area about the size of the star and its halo. The Marquee tools are on the tool bar, usually near the top, and the default tool is a rectangle depicted by a dashed line. Press down and hold on it to see the other subtools and change to the Elliptical tool. Shift-Click on a point near the star and keeping the Shift key down drag the cursor to draw a circle about the size of the star and its outer halo.
  3. Enlarge the selection area using Select > Modify > Enlarge so that the selection is much larger than the star and its bloat:
  4. Feather the selection using Select > Modify > Feather so that the outline of the selection area is still quite a bit larger than the star's bloat:
  5. Create a Curves adjustment layer (use the "Create new fill or adjustment layer" mini-icon in the Layers Palette)
  6. Use a downward curve to darken the halo as in the figure.
  7. If you think the star no longer gives the impression of being very bright, adjust the highlight portion of the curve as in the diagram to make the star brighter. (Better yet, reselect it with a much tighter feathered circle and stretch it a little.)
  8. When you're happy with the changes, merge the layers and save your file. If you need to process several stars it might be best to save intermediate versions.

Obviously this process entails some trial and error concerning the size of the selection, the amount of feathering, and the specific curves to apply.

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