Control Highlight and Shadow Separately

When you sharpen an image, Photoshop will add a dark halo on one side of an edge and a bright halo on the opposite side of the edge. When you're working with dark backgrounds (like a deep blue sky), the bright halos can be rather easy to see (Figure 12.66). That's when you might want to try controlling the bright and dark halos separately so that you can minimize the bright halo while maintaining the dark one. You can accomplish that by making two duplicates of the layer you want to sharpen. Then, click on each of those duplicate layers and set the Blending mode at the top of the Layers palette to Lighten for one and Darken for the other (Figure 12.67). Now you can sharpen the two layers separately; the setting you apply to the layer that is set to Lighten will control the bright halos, while the setting used on the layer set to Darken will control the dark halo (Figure 12.68).

You can also use the History brush with its blending mode set to Lighten or Darken to rid your image of sharpening-related halos. Use Darken mode to remove the bright halos and Lighten mode to remove the dark halos.