Lighting Ratio

Setting up a maquette outdoors in the sunlight gives me clues about the placement of shadows and the lighting ratio. 

The term "lighting ratio" is defined as the comparison between the key light and the fill light. In outdoor sunlight, the key light is the sun and the fill light is the combination of the skylight and reflected sources. 

The higher the lighting ratio, the greater the contrast, and the lower the ratio the lesser the contrast. 

As I explain in my book "Color and Light," 

It’s easy to underestimate the tonal separation between the light side and the shadow side in sunlight. When lighting experts set up artificial lights for a movie shot, they call this separation the lighting ratio, and they usually try to reduce it to cancel the unflattering effect of harsh or dark shadows.

As artists we may want to do the same, depending on the feeling we want to create. But most often, beginning painters tend to ignore the dominance of direct illumination and play up secondary sources too much.

If you’re counting steps on a value scale from one to ten, you might typically see five steps of tone from sunlight to shadow, or two f-stops on a camera’s aperture setting. The separation would be reduced if there were high clouds, hazy atmosphere, or a light-colored ground surface.

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Color and Light: A Guide for the Realist Painter is also available signed from my website.

Tutorial videos: How I Paint Dinosaurs and Tyrannosaurs: Behind the Art