Studio Lighting II: Key and Fill

Before there was light, utter darkness moved upon the face of the world.

That might sound sort of biblical, but it’s the best way to think about lighting. Everything starts out as black as night until the light comes into the scene.

It’s easy enough to see how the main light source illuminates the form. But it would be a mistake to think of the shadow side as the absence of light. There’s light filling the shadow, too, but it’s just another kind of light from a weaker source.

Here’s an example. I’m posing here with a kaffiyeh as a reference for a painting of Arthur Denison on page 119 of Dinotopia: Journey to Chandara. The main light, from the baby spot, is coming from above and to the right. The shadow side is getting weak, cool light coming from the skylight and the north window at left. The shadow side of the form wouldn’t be anywhere near black unless I was in a windowless room with black velvet wallpaper.

Here’s an oil study of a model lit from a low light coming from the left. Photographers call this main light the “key” light. The shadow is getting greenish light bouncing back from a cloth that was behind the model. This light that enters the shadow is called the “fill” light. In TV and movie lighting, a second, weaker electric light usually provides the fill light. But most often we painters use natural reflected light for the fill.

This head in profile has the key light coming from the left, shining directly in the face of the model. The fill light is much weaker, making an extreme “lighting ratio” of key to fill light. The greater the ratio, the more low-key or dramatic the form will appear.

Note that I placed the light in the direction of the subject’s gaze. I think we all have a basic instinct to look toward the light of a window or a doorway, and to me it is satisfying in some deep way to look at a face that is oriented toward the light. Next time you’re sitting absent-mindedly in a dark room, take note of the fact that you instinctively rest your gaze on the lightest area of the scene.

On this half-hour oil sketch from life, I used the baby spot with an orange gel for the key light coming from the right. I set up a second fill light with a contrasting blue-green gel. The brightness of the fill light almost equals the key light, leading to a close or “high key” lighting ratio. It looks unnatural and weird simply because such a relationship could not happen under natural conditions.

Only a few places on the face are not touched by either the key or fill lights: the side of the nose, the edge of the eye, the lower cheek, and the neck. As a result those areas are quite a bit darker.

Check back in a couple of days for the last in the studio lighting series: edge lighting.