I wanted to learn how to take photos in extreme lighting conditions, i.e. bright slashes of sunlight, and to manually lock exposure for the part of the face in the light, rather than to expose as an average across the face. This creates a HIGH CONTRAST images, where there is a an extreme difference in the contrast (white vs black).
In contrast the below image has more of a MEDIUM contrast as there are lots of grey tones.
What is the effect of this on the viewer? Low contrast images have a lighter feel and therefore are more relaxed. High contrast images feels heavier and more serious or suspenseful.
When thinking about the quality of the light beyond the CONTRAST (which relates to the range of tones) there is also KEY (which relates to the distribution of light and shadow). High-key is low contrast lighting – so the image is EVENLY LIT and there are MINIMAL SHADOWS. This makes it feel upbeat, and it is flattering, and it is also versitile because and the light works from most angles whilst retaining the same feel.
Low-key lighting is high-contrast lighting with some of the image being bright and some being dark black shadows. The light can focus the audiences eye and separates the subjects from the background surround – and therefore is very specifically set up in relation to the direction of light (i.e. not as easy to move around camera angles as with high-key light). It is dramatic and can add feelings of FEAR or INTIMACY / ROMANCE.
Learning Portrait Photography 