By David Rosenthal.
In this tutorial we're going to cover what to do when you've got a wide range of tonal values from dark shadows to bright highlights in a single image. You can read about using Shadow/Highlights recovery here, and it's a great tool. But what if you could pull all of those tonal values out of one image, and not even need to use Shadow/Highlights?
Well, if you shot in RAW, then you're in luck, because RAW will give you the power to process out two different exposures, one for the shadows and one for the highlights. Once you have those two exposures you can easily blend them. I'm going to show you how.
This image here (coutesy of wxwax), is a great example of the challenge faced when the range of the scene is beyond the digital sensor to capture in one exposure. I've set the exposure and shadows slider in ACR to their maximum, in order to not clip either of them. The result is what you see here. We can do better.
CLICK ON THE IMAGE TO SEE A LARGER VERSION.
And here is the one that I exposed for the shadows.
What you need to do is to get the two images in one PS document, with the lighter one on top. There are several ways to do this. You can copy/paste, or cmd-shift-drag on the Mac (cntl-shift-drag on the PC). However you do it, get the lighter exposure on top of the darker one.
And your layers palette should look like this. Lighter image on top, darker on on the bottom. Next you're going to select the bottom (darker) layer and select the highlights (cmd-opt-~ on the Mac, ctl-opt-~ on the PC). This will select the highlights of the darker image, leaving a bunch of "crawling ants" to show you what you've selected. After you've done that, click on the layer above, and click the add mask icon at the bottom of the window (the white circle in gray box). This will create a mask for that layer, but that mask will be the opposite of what you want, and you'll need to invert it (cmd-i on the Mac, ctl-i, PC). Now you should be seeing the highlights from the bottom layer showing through your uppermost layer.
Next you're going to select the bottom (darker) layer and select the highlights (cmd-opt-~ on the Mac, ctl-alt-~ on the PC). This will select the highlights of the darker image, leaving a bunch of "crawling ants" to show you what you've selected.
Good so far, and you're almost done.
Now, copy the bottom (darker layer) on top of the second layer. Select the highlights of the second layer (cmd-opt-~ on the Mac, ctl-alt-~ on the PC), then select the top layer, and Apply Vector Mask again. This time you can leave it as it is (no need to invert).