The parts that come together to create a low key image are a black back ground and dark clothing, although I personally find that dressing my subjects in white or black has great impact.

There are three type keys High Key, Middle Key and Low Key.

Fig.1

The term low key relates to the tonal range's in an image,what we are aiming for when we take the photographs on a black background is that we are trying to achieve an under exposure which will create a loss of detail and a pure black background. Remember a good low-key lighting set included a full range of tones from a white to black, however a low-key image is also made up of predominantly darker tones.