The principles of light retouching are based on first understanding the type of face being presented to the camera, and then lighting that face with the most flattering light—a light that will accentuate the positives and minimize the negatives. With the wrong light a pretty face can appear unattractive, and to a certain extent the reverse is also true.
Starting with a soft light source—window light, a softbox, a large white reflector or silk—you’ve got a good start for achieving flattering light for almost all faces. That’s because soft light minimizes hard shadows and texture—both of which are the telltale signs of unflattering portrait details. The problem is that for round faces a broad, soft light can enhance roundness and weight, so the light must be positioned just so. A frontal soft light on a large round face will make the face appear even larger and rounder, whereas split lighting—with the light to the side—will create a visual slimming effect by making the illuminated part of the face appear thinner, letting the opposite side of the face fall into shadow. While true split lighting may be overly dramatic, the principle holds true that you should move a light toward a sidelighting position to help thin a face.
The reverse also holds true. If a face is thin or angular to the point that you want to soften it, that same soft source is important, but it should be placed closer to the camera in order to illuminate more of the face, eliminate strong shadows and generally make the face appear more round. This is how light placement becomes the first step in retouching with light.
If you position the main light high, it might flatter eyes but it could also accentuate a crooked nose. A lower key light might make the nose look great but it could also bring out dark bags under the eyes. Adding a second light—usually an eye light—is a great way to achieve the best of both worlds. That second light can be an on-camera flash at a lower fill level, or maybe even a snooted or tightly focused strobe to provide just a bit of sparkle and illumination in the subject’s eyes. Use of flags to keep the eye light from spilling into other parts of the scene is helpful as well.
If you’re photographing someone with prominent ears, first consider their head position. A slight turn so that they aren’t looking straight into the camera can help hide protruding ears. Secondly, try lighting only the face and shading the sides of the head so that ears recede in prominence. This can be accomplished with the careful placement of a flag or other scene element—like a tree, for instance—to put the emphasis on the face and off the ears.
No matter what kind of face you’re faced with, understanding a few simple lighting tricks can help you make a beautiful portrait by retouching not only during post-production, but with the way you light the shot. And that’s going to make your subjects doubly happy when the see the finished product.