What does the key light in photography refer to?

The key light in photography is indeed the main source of light that defines the subject. It plays a crucial role in establishing the mood, depth, and overall composition of the image. The key light determines how features and textures of the subject are illuminated, influencing the visual narrative that the photograph conveys. By positioning the key light strategically, photographers can highlight aspects of the subject, create contrast, and establish a clear focus, which lends clarity and emotional impact to the photograph.

In essence, the key light serves as the foundation upon which the rest of the lighting setup is built, guiding the viewer's eyes to the most important elements of the scene. This makes it a fundamental concept in lighting techniques used in photography, emphasizing its significance over other types of lighting such as fill or ambient light.