Want to make a mysterious portrait? Or maybe you want to show the shape of something without showing all of its detail. It sounds like you might want to make a low-key, edge-lit image. The technique is simple and straightforward, and the result is dramatic. The key is to illuminate the subject from behind and let its camera-facing side fall into a deep, dark shadow.
To start your mysterious image, choose the perfect location. Your primary goal is for the background to go dark, maybe even pure black. So choose a location that has a dark area behind the subject. In the studio, this may be a roll of black seamless paper. Failing that, if you put a lot of distance between the subject and the background, it naturally will fall to black once you backlight the subject with a high-powered strobe. With distance between subject and background, it’s always easier to keep the light intended for the subject from also illuminating the background—even if that light is coming from behind.
If the subject is a person—or really, the human form—I like to use a specular light source. A diffused light, if not placed directly behind the subject, tends to wrap around more and doesn’t provide a crisp, thin line of light the way a specular light will. If I’m shooting something man-made, however, or if what you want is a little more wraparound light, a diffused light may be helpful, as it can reveal a bit more.
Working with a single light source, you can position it directly behind the subject so that the subject itself will hide it from view. The distance of the light will be determined largely by the size and shape of the subject. For a standing person, for instance, the source might be 10 feet away. By positioning a single light behind the subject, it will create a thin band of light outlining the subject’s shape. This is called a rim light.
You can also create a rim-lighting situation outdoors with the sun. Positioning the sun in your scene behind a tree, for instance, will rim-light the tree if you expose for normal daylight. Positioned behind a person, it will have the same effect—although you’ll give up a bit of control over the background and fill compared to working in a controlled studio situation.
In the studio or outdoors, you’ll frequently have the option to position the light above and behind the subject. This is another approach for producing a mysterious, low-key look, but the light is more likely to spill to the front of the subject and fill in more details—as evidenced by the second example shown below.
In a studio, or at least in a situation where you have access to multiple light sources—handheld flashes, studio strobes or continuous lights like LEDs or fluorescents—another approach is to use two lights behind the subject. Rather than positioning these lights directly on the lens axis, however, they should be behind the subject and to the side far enough to be out of frame. In this way the light will wrap around the edges of the subject a bit more, helping to hint at the subject’s shape and texture.
In a two-light scenario with a person as the subject, I like to position one light back and to the left with the other back and to the right, out of frame in each case, and positioned high enough that the light is above shoulder level. Keep an eye on the shadow created by ears with this lighting because, depending on the subject’s head position, the ears can cast a strong, unappealing shadow across the subject’s cheek. To remedy this, move the lights farther out of frame or adjust the subject’s head position so that the shadow is not so dramatic.
Some photographers take this two-light edge-lighting approach even further and use multiple lights with grids or snoots to focus the light, and then each light is aimed at a different portion of the subject. This might entail one light overhead and behind the subject to illuminate the head and shoulders, then on each side of the subject a focused light for the shoulder and arms, and another for the legs and lower half of the frame. The approach remains the same even though more lights are involved.
The challenge with this type of two-light (or multi-light) approach is fighting lens flare. I like to use a flag placed between the light source and my camera, near the edges of the frame. Then you can simply stand in the subject’s position and look at the lens. If it’s in shadow, flare has been eliminated. (If you don’t fight flare you’ll find your blacks aren’t so black and the image will lack contrast and sharpness. It’s a real bummer.)
The last consideration is fill light. Should you add some? The answer is an unequivocal “maybe.” Some subjects look better with a bit of fill light illuminating a hint of detail, while others prefer a pure black shroud of mystery. If you do add fill, should you add much? Most definitely not. Should there be a frontal key? No way. If you want any frontal detail at all, you want just a little bit. Nothing will kill the sense of mystery and drama faster than too much fill from the front. With just a backlight illuminating your subject, the shot is sure to be low-key and mysterious, and when that’s the look you’re going for, nothing else will do.