By David Rosenthal.
When you need to get more detail out of the shadows of an image, the Shadow/Highlight Tool is the trick.
First, make sure that you do this on a new, duplicate layer. This is very important for checking your work and for scaling back on it, if necessary.
To make a new layer, select your current layer and type Command-j (Control-j, PC). You can rename your new layer, if you like to keep track of your work.
Now, go to Image>Adjustments>Shadow/Highlight...
When you open the Shadow/Highlight tool, it is set by default as you see here.
Which results in an image that looks too overprocessed, and has too much of the shadows recovered for an unnatural look. It's very easy to over-do S/H.
Since you've made this correction on a duplicate layer, you can fix it without opening S/H again: just lower the opacity on the S/H layer. For this image I had to lower it to 30% to get a nice result.
Toggle back and forth on the eye button in the layers palette to turn the visibility of that layer on/off to check your work.
Or, you could go back into the Shadow/Highlight tool and lower the amount. In this case I used 17%. Anything under 20 is generally pretty safe.
Just remember: Shadow/Highlight can be very destructive and can ruin parts of your image. Be careful with it and remember that under 20 is pretty much safe...
Also note that you could save your settings for later use, or you can save them as your defaults.
Which results in this image.
There's plenty more to do with this image to bring out the eyes, correct overall, but hey, now you've got a new tool under your belt!
Here the animation mimics the toggling on/off of the eyeball in the layers palette.
Keep in mind that no Photoshop tool or technique works alone. Try combining Shadow/Highlight with a Layer Mask. You can find a tutorial for using Layer Mask HERE..
Discuss Shadow/Highlight Tool at Dgrin