Millions were treated to the total solar eclipse in the US this week. Aside from a surreal source of inspiration, there is quite a lot this unmatched spectacle can teach us about light and painting.
To help us consider the sun’s lesson, we look to a fascinating effect that accompanies an eclipse. The shadows cast by objects will take on a bizarre pattern as the light from the sun is occluded by the moon. The eclipsed light through a tree will generate thousands of overlapping crescents upon the ground.
The reason this happens comes from the diffraction of the sun’s light off of the surface of each leaf. Diffraction is a physical phenomenon, in which light is redirected or bent around the edges of an object. The many light rays originating from the crescent sun approach each part of the leaf from slightly different angles. After diffracting from the leaf’s surface, those individual light rays will project a flipped image of the eclipsed sun on the ground. This is, of course, exactly how a pin-hole camera works.
Well, that’s interesting, but how does it help us as painters? If we realize that this diffraction effect is happening all the time, even under normal lighting conditions, we can take advantage of this knowledge and render more realistic images. Consider the diffraction of normal sunlight through a tree. What may not have been obvious before, should now be clear: the tree’s cast shadow on the ground is made up of hundreds of circles of light! The projection is composed of overlapping circles, because the sun’s image is (normally) circular.
If you’ve struggled to paint this type of fuzzy shadow before, now you may have more success. You can use a round brush to build up the shadow’s pattern through the layering of various circular dabs of light. Each dab of paint should be varied in value, and depending on the surface upon which the shadow is cast, the chroma may vary by location. If you build up this effect enough, a realistic portrayal of your subject will begin to take form. Of course, always remember to use your discretion and observe your subject with a discerning eye. Without this consideration, the effect your creating may look like a cheap trick and produce a more shallow, kitschy appearance. If done correctly, you will have a pleasantly soft impression of the tree’s shade.
Our lesson about diffraction can also inform our decisions about studio lighting for subjects painted indoors. The smaller the source of light (e.g. a pinhole, LED, small window) and the further the light is from your subject, the crisper your subject’s cast shadows will appear. Those who witnessed the eclipse may have noticed the crispness of their shadow just before totality. On the other hand, the larger the light source and the closer it is to your subject, the more diffused the cast shadows will be. Rembrandt used to take advantage of this effect. He often would place his subject in an unlit room beneath a single skylight — a large source of light at a relatively close distance. This quality of light produced his signature softness and moody atmosphere.
Featured eclipse image credit: Yuri Shwedoff