High Pass Filtering

Sometimes it's fun to see how much detail you can coax out of nebulae galaxies. One way to do this is to use a high pass filter with an assist from masks.

  1. Open your image
  2. Create a copy in a new layer (using the duplicate layer mini-icon)
  3. high-pass filter the copy (Filter > Other > High Pass...) Adjust the radius to your liking. Don't worry about how washed out the image becomes, nor how strange the stars might look. For the most part those strange stars will be masked out.
  4. Create a Hide All mask (Layer > Layer Mask > Hide All)
  5. Set the foreground color to White (overlaid squares at bottom of toolbar) and use the brush to paint in the parts of the image that you want to have show the filtering. Usually you'll only be painting over the brighter parts of a galaxy or nebula.
  6. Apply a Gaussian Blur (radius 20-30 or whatever works) to soften the edges of the masked area.
  7. Change the layer mode from Normal to Soft Light for a soft blending. You can use other modes, too, but some like Hard Light and Vivid Light can be fairly harsh. Sometimes the harshness can be compensated for with a change in layer opacity.
  8. If you find that the high pass filter has increased grain too much, click on the layer's thumbnail and apply a Gaussian blur with radius around 1.
  9. When you have the image the way you want, merge the layers and save your image.

Go easy on the high pass filter--it's easy to overdo it, leading to harsh unrealistic images.

Return to main Processing page