Different light types - low key
If high key is predominantly light then low key is predominantly dark, but the same rules apply. A dark image risks being merely underexposed and uninteresting. As with the high key image it is the opposites that create the contrast and relief. In the case of a low key image, strategically placed highlights create the mood and bring the image to life.
In the image of the door the atmosphere is almost tangible. The small areas of light seem to be trying to burst forward creating a tension and inviting anticipation in the viewer as to what may lie behind the door. The overriding sinister and mysterious aura is typical of successful low key images.