Contrast Masking - Rescue highlights and/or shadows

This is a technique with a wide range of uses, for example, balancing a bright sky against a dark foreground, rescuing blown out sky or specular highlights, unblock heavy shadows.

1. Duplicate your Background layer, name it "Contrast mask", this new layer should be above any adjustment layers.
   


2. With the Contrast Mask layer selected go to, Image / Adjust / Desaturate. The layer will now become monochrome, as will everything below it (for the moment).
   


3. Go to, Image / Adjust / Invert. This turns the Contrast Mask later into a negative.
   


4. Double-Click on the Contrast Mask layer on the Layers Palette and select Layer Options. Select Overlay blend mode.
   


5. Go to, Filter / Blur / Gaussian Blur and set a value of between 10 and 250. This will enable you to fine tune the effect on your final image.
   

Further fine tuning can be achieved by adjusting the contrast layer opacity. Finally use Levels and Curves to tweak the final effect. It is also possible to restrict the effect to specific areas by using a selection around a specular high light for example.

Before contrast mask

After contrast mask

See finished image here.