A very simple technique that allows you to produce interesting images is the low-key treatment. It is actually a combination of lighting technique, choice of background and color of clothes as well as entails the use of a very specific law in physics, known as the inverse square law. Low-key treatment or lighting setup isn’t that much of a niche thing. You must have seen it before. One of the likeliest of places being cinema where directors often resort to this treatment for scenes such as where a suspect is being interrogated or in general scenes that are intense or need a bit of suspense in them.
Low-key images have a lot of shadows in them. This is the exact opposite of high-key images which are identified by an overabundance of light and a lack of shadows. Hardly, about 10-20% of the image has any light in it and the remaining image is either in complete darkness or in varying shades of grey. The histogram, naturally, will be skewed towards left. Having said that I personally don’t mind a small highlighted area, which kind of accentuates the drama in the image while adding a bit of contrast. Yes, contrast is another aspect that you need in low-key images. Contrast is the difference in tonal range between pure white and pure black in an image.
What you Need
In order to be able to use this technique you need a DSLR, a lens, a tripod, a dark background – preferably black and as little light as possible. For beginner photographers, thus, this is very easy to setup. They don’t need too many lights. The dark background will give a sinister looking backdrop for your images, making the viewer search for something to focus on and being unable to find anything in the darker areas come back to the illuminated areas in the image. Thus, low-key can also lead to emphasis on the most important aspects of an image.
Uses for Low-key Photography
Apart from portrait imagery, low-key is treatment is often used in high contrast fashion shoots, to highlight shapes and forms, such as in boudoir photography, in upmarket product images such as watches, wines, personal products and a host of other areas. It is also used where textures are required to be highlighted.
There are several lighting techniques that you can use with a single light – and a single light is all what you need. The basic thing that you need to remember is that you need a lot of contrast regardless of the lighting setup. Thus, side lighting is more suitable than illuminating the subject from the front. Having said that, the first arrangement that comes to my mind is Rembrandt lighting. Rembrandt lighting is named after the famous Dutch painter who used it quite consistently in his paintings. It is recognized by the small triangle of trapped light on the cheek of the subject facing away from the light source. Place the light on to the camera right (or left, as per your preference) and just above the eye line. Perfect it till you see the small triangle of light on the subject’s cheek.
The Inverse Square Law
The inverse square law is a very critical law and an important piece of information to keep in mind when using artificial lights for your photography. In the context of low-key photography it is even more important because understanding the law will allow you to maximize the effect of light fall-off. It basically states that the intensity of light drops by the inverse of the square of the distance between the source of light and the subject being photographed.
As per the inverse square law, light fall off is more dramatic (and significant) over the initial distance. This means the difference in light from the illuminated side and the one away from the light source is more. As the distance increases the difference in light becomes less dramatic from one side to the other. This should give you a hint as to what distance you should set your subjects from the light source. Ideally, your subjects should be closer to the light source for the maximum contrast.