Monday, August 10, 2009

Photoshop CS4 action: High-pass sharpening

My good friend and fellow photographer Rich Legg wrote an article almost two years ago about how to use the high-pass filter to sharpen an image. I made a mental note of it in passing, but didn't do much with it since I was using Paint Shop Pro at the time and it has a built-in method to do this in one step. When I switched to Photoshop several months ago, I went back to his article to remind myself how to do it.

In his article, Rich outlines the four step process:
  1. Copy the layer you want to sharpen.
  2. Apply a high pass filter to it.
  3. Set the radius to around 4.
  4. Set the blending mode to Soft light for a mild sharpen or Overlay for a stronger effect.
Simple as this is, I created an action to make it a single operation. The action file can be downloaded here.

To use it, click the link above and save the file to your computer. In Photoshop, on the Actions menu, select Load actions. In the open file dialog, go to the location the file is saved, select and open the file. You should get a action group called HP3's sharpening with two actions in it, one for strong sharpening and one for mild sharpening.

To use them, open an image, highlight the background layer, click on one of the two actions and run it. You should get a new layer and the high-pass filter radius dialog. Adjust the radius as desired and click OK. You should see your image sharpened. You can enable and disable the layer to see the effect of the action.

A couple notes:
  1. The radius value of 4 that Rich recommends for the filter is image dependent. Use higher values for more sharpening and/or a larger image. Use a smaller value for less sharpening or a smaller image. The actions I've recorded use a value of 5 as a default since I've found that seems to work better for me with the types of images I typically work with. If you set this too large, you'll get a light halo effect around the edges of subjects in your image.
  2. I've set the Opacity of the sharpening layer to 50% as a starting point. Again, this seems to be a good starting point for me on the images I edit. Like the radius value, it can also be increased for more sharpening or decreased for less.
If you have any questions, problems or suggestions, leave a comment and I'll try to address the issue. Have fun!
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