Layer Masking
One of Photoshop's most powerful tools, masking lets you control how two ( or more ) images are combined. In this tutorial we're going to use two different versions of the same photo, first to create a Selective Color image, then to improve the dynamic range from two raw conversions, and finally we'll explore why adjustment layers are so useful.
Contents
Preparation
Before we begin, we need two layers stacked one on top of the other. These should be aligned pixel-for-pixel, which means shooting from a tripod if more than one exposure is necessary. On the other hand, you could make additional layers from copies of the background.
( Note: You get the files into two layers by opening both of them, then copying one and pasting it on top of the other. Use the image you want to display more of as the top layer, and the image that will show the least as the background layer. )
Masking
We're going to use normal layers with different versions of a photo.
Selective Color
In this example, the second layer is a copy of parts of the first, and the background has been converted to black and white. This effect only requires one exposure, making it suitable for portraiture, sports, or wildlife.
Click for: Finished | Layers | Background | Color
The eyes are already perfect, although the blue doesn't stand out very much against the lashes and shadows in the eye sockets. On the other hand, the area around the lips is painfully obvious, and a very poor job.
First, we'll create a mask over the layer with the mouth. Click the button at the bottom of the Layers palette that looks like a white circle, highlighted at left. You'll see a white box appear next to the thumbnail for the level; this is a thumbnail representing the mask for that layer. We haven't hidden anything yet, so it's solid white.
Click the mask ( the white thumbnail ), and then switch to the brush tool. The foreground color should be black, meaning to hide anything you paint over. White means to show anything you paint. Painting green is like using black and then reducing the opacity.
Start painting the red around the lips, and watch the color disappear. It can help to zoom in, sometimes beyond 100 % view, to decide which pixels to show and which to hide. This is always more difficult than the technical work.
If you make a mistake, or change your mind, paint it over in white, and you'll "unhide" the layer you're working on. Forget the History Brush!
( Note: The eyes are perfect because they're easy to select with the Magic Wand tool. The lips are more difficult in such a warm-toned photo. Of course, I also exaggerated the problem to demonstrate how to solve it via masking. Still, if you can build an accurate selection before you copy a new layer, it will save you a lot of time masking your margin of error away. )
Tonal Range Expansion
"High Dynamic Range" or "HDR" photography is a way to get around technical limitations - the amount of contrast that can be recorded in a scene. Although many photographers buy software like Photomatrix, Photoshop can accomplish similar results given the same series of exposures. It takes longer, but gives you a lot more control over the final result. This is done in the same way as the selective color effect, but using multiple extractions from a raw file, or ideally multiple exposures.
Adjustment Layer Masking
This isn't very different from normal layer masking, except that we're going to make the changes in a "non-destructive" way.