Sometimes the lighting for an image is just
a little bit off. Perhaps it's unbalanced, or there's a
shadow, maybe an unwanted highlight... You can use Photoshop's
Brush tool to even things up. (This technique is available for
any recent version of Photoshop.)
In this image, PhotoSpin.com's #1150063,
you can see the shadow to the left of the subject's mouth is
produced by the upraised arms in the original. In the cropped
copy, the shadow is a bit distracting. We'll paint it away
using the Brush tool set to the Luminosity blending mode and
an opacity of 15%.
Hold down the Option key (Mac) or the Alt key (Windows) to
temporarily activate the Eyedropper tool and click on an area
of skin that you want to match. That sets the foreground color
to the selected skin color, including the luminosity of the
area.
Now we can paint over the
shadow area to match the luminosity. We can also lighten up
the shadows to the lower-right of the mouth and that to the
left of the nose.
And while we're at it, we
can even paint over the slightly-too-light cheeks, too.
Switching the Brush's blending mode to Color, we can even out
the cheeks, producing a more uniform skin appearance
throughout the image.
Subtle changes, yes, but
effective in smoothing the appearance of the skin without
losing the original charm of the shot.