I do a lot of selective adjustments using layer masks, which
sounds more difficult than it is. But it was a concept that was difficult for
me to grasp, so I thought I'd take a stab at explaining it for new
photo-finishers.
Here's a photo of mother and child that needs adjustment to better
display their beauty.
A global levels adjustment, will work, but also brightens the
background, which I'd rather avoid.
One way around this is to create a duplicate layer [press ctrl +
J], apply the global levels adjustment to the upper layer, and then use an
eraser to remove the parts of the top layer that didn't need brightening.
Image control: Zoom
out | Zoom
100% | Zoom
in | Expand
/ Contract
| New window
The problem with this approach is, should you find you made an error, you might have to go back to the beginning and start
all over again. Fortunately, Photoshop offers a more forgiving and elegant
solution... layer masking.
After you've created the duplicate layer and globally adjusted the
levels, go to [layer - layer mask - hide all]. You'll see that a black square
has been added to the icon for the top layer, and that the levels adjustment
you made has been hidden.
Image control: Zoom
out | Zoom
100% | Zoom
in | Expand
/ Contract
| New window
Now set
the foreground color to white, click on the black mask icon, and select the
paintbrush tool. Wherever you paint on your picture, you'll change the mask
covering that portion of the image to white, letting the levels adjustment show
through.
Oops! Now you see why I got a low grade in coloring in kindergarten.... I can't
paint between the lines :?. Those lighter colored
blobs on the background are where I screwed up and painted white on parts of
mask that should have been left black. No problem! I'll just change the
foreground color to black, and carefully paint back in black on those portions
of the mask.
This masking approach works on any change you'd like to make to
the upper layer, including levels, sharpening, hue/saturation, etc. For
example, the amount of sharpness of this picture works well for the child, but
isn't very flattering to the mother's mature skin, so I created a duplicate
layer, and applied 1 pixel of Gaussian blur to the
picture. Then I used a hide-all layer mask, and painted white on the mask over
areas where "character lines" needed to be softened, leaving the rest
of the image sharp.
I can guarantee you that once you understand
the concept, you'll find countless uses for layer
masking.