I'm aware of curves and hue / saturation to make skin tones match but for some reason I have a hard time to get them right in this case. It seems like the areas are somewhat desaturated so the hue tool has trouble to limit the selection to just these color ranges. Of course I could soften the skin completely but this wouldn't look good either... Any other recommendations how to deal with this specific case?
Frequency Separation is the technique, you are looking for.
With this, you separate the image into 2 layers. One containing more of the color information and one containing more of the texture and details.
In very short steps:
- Duplicate (cmd+J) your Background layer twice. Rename the top layer "high frequency" and the bottom "low frequency." Then group the two layers (select the two layers & cmd+g)
- With the Low Frequency layer selected, Filter>Gaussian Blur filter and choose a pixel radius with which all the fine details will be blurred. I have mine set at 3.7 but there are some photographers who will set it to 5 so this is just up to your preference in terms of how much detail you want. I personally prefer a lower blur.
- Now select the High Frequency layer and go Image > Apply Image and use these settings: For 8-bit images-> Layer: Select “Low Frequency”, Invert: unchecked, Blending to “Subtract”, Scale: 2, Offset: 128. For 16-bit images-> Layer: Select “Low Frequency”, Invert: checked, Blending to “Add”, Scale: 2, Offset: 0.
Now you're ready to use the clone stamp & spot-healing brush on the "low frequency" layer for your skin problems. Or use blur or healing brush to even out color.
Video Tutorial by phlearn - they also have that as a photoshop action which saves you the hassle of creating the layers manually