Light Spill

I had the morning free yesterday in Allentown, Pennsylvania so I set up my chair in an alley called West Silk Street and did this little gouache sketch.

I was interested in an effect that I've been calling "light spill." I've noticed this effect in old photographs or in pictures taken with a camera that has a dirty lens.

When an extremely bright field of light is surrounded by very dark forms, the light spills over into them. Even though those forms appear very dark near the sky, I tried not to paint them that way. The color of the light spill is the same as the color of the source of light, so a blue sky will spill blue light and a warm building will spill warm light.

I took some photos while I was doing the sketch. In these two details from the same high-key exposure, you can see the effect of light spill on smaller forms interpenetrating the bright areas. Note how the wires and the streetlight in the top detail are blue where they intersect the sky. The wires turn orange where they intersect in front of the warmly lit rooftops.

Photography has a disadvantage over painting in such super-high-contrast situations, because to really see the light-spill effect in the dark areas, you have to burn out the exposure in the light areas, which appear white in the photos above. 

But in the painting (detail above), I could hold some chroma in both the sky and the building. Gouache is a really nice medium for such experiments.
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Materials: Moleskine watercolor notebook, Winsor & Newton gouache, Caran D'Ache Supracolor pencils
Color and Light book
Related previous posts:
Color Corona