High Key Lighting - Definition

High Key Lighting is a lighting technique that involves using mid-tone greys through to bright whites. It enhances the highlights of somebody's face. In a high key photo, there is a noticeable lack of contrast and hard shadows. The images are generally very bright.

Although this has been converted to black and white, it is still clear that it was taken using high key lighting. The background has been lit using backlights and overexposed, most likely by two stops more than the key light. The Key light was either a beauty dish or a soft light, as the lighting on the subject's face is very soft. I can guess that in this image, a fill light wasn't used, as the shadows made by her face were minimal and not very full.