Dilate Erode Combine
- A hard mask is clean but its edges, especially on hair, are too hard.
- A soft mask has great edges but is noisy in the black and white ares.
- Combine the two!
- Make two masks: a soft one (using a Color Range) and a hard one (using whatever you want).
- Duplicate the hard one and erode one by a few pixels and dilate the other.
- Copy the erode and paste it into soft. Then go to Edit / Fade and set the blend mode to Screen. This will render the black of the pasted erode invisible as it is the neutral color for the screen mode (edit Fade dialogue box below).
- Copy the dilate and paste it into soft. Then go to Edit / Fade and set the blend mode to Multiply. This will render the white of the pasted erode mask invisible as it is the neutral color for the multiply mode.
The image below is a graphical representation of this process. The green area represents the hard, interior eroded mask (applied via a screen blend), the red area represents the hard, exterior dilated mask (applied via a multiply blend). Between the two the original edge of the soft mask can be seen.