Selecting Pixels by Brightness

Just ran into that time again when I want to preserve the shadows in a nicely backgrounded image. I usually end up saying, "screw it," and mask out the object and add in a fake background. Blah.

To select pixels based on their "brightness" (luminosity), ctrl-click the RGB channel.

To keep the shadows, invert the selection, and combine it with a masked layer of the object in question.

Frequency Separation

Using the high-pass method (vs. image-apply):

1. Create two duplicate layers ("texture" on top and "tone" next)
2. With regards to the texture layer
1. Apply a high-pass filter using a pixel radius to capture all fine details but not tonal or volume changes
2. Blending mode to Linear Light
3. Opacity to 50%
3. Gaussian blur the tone layer with the same pixel radius used for the high-pass filter