Thursday, February 18, 2010

Light and Form, Part 3

In soft or diffuse light, such as overcast light, there is no distinct light side, shadow side, terminator, or core. All of the upward facing planes tend to be lighter, since they receive more of the diffused light from the cloudy ceiling.

The photograph of the ball shows the quality of overcast light. The cast shadow has no definite edge. There’s no clear division between light and shadow unless the form turns on a hard edge.

Here’s an example of overcast light falling on the figure of David Balfour in the N. C. Wyeth illustration “On the Island of Earraid,” from Kidnapped. The planes of the figure’s skin and clothing get lighter where they face more toward the light sky. (The sharp tonal changes in the background are dramatic plane changes in the rock.)

Another example of overcast light is this portrait of a girl by William Bouguereau. The form doesn’t have a light side and a shadow side in the conventional sense. The vertical plane of the dress and the upper arm are both darker than the forearm and the leg of the dress, which catch more light because they face more upward.

The coolness of this light source is evident from the relatively warm shadow under the chair. Occlusion shadows require especially careful attention in diffuse light, often appearing as notably sharp accents in the work of Bouguereau and Rockwell.

Light and Form, Part 1

Light and Form, Part 2
Light and Form, Part 3
You also might be interested in these posts:
Occlusion shadows
Reflected light.
More about all this in my book: Color and Light: A Guide for the Realist Painter


yama-haha said...

Mr. James I'm very thankfull for this series of tutorials. These are just awesome, somehow the common and well known pack of informations, but yet still something that opens my eyes, and it increases my total decgree of work - thanks :).

Oscar Baechler said...

I love this about Bouguereau, one of my favorites. He usually uses exceptionally diffused scenes, and I had a huge "aha!" moment when I first connected the dots between Ambient Occlusion in 3D software and how it applies to representational scenes.

Check out any GIS for Ambient Occlusion and you can see the fundamentals of Bouguereau all over it!

Stephen James. said...

We had to do an assignment like this once.

Interesting trying to render a sphere without resorting to the easy to read shorthand of a highlight.

Tyler J said...

Another great post. The Bouguereau is beautifully done.

I am curious as to why the light source can said to be cool based on the warmness of the shadow. Is this a rule of thumb or something hard and fast? Surely there are exceptions.

I realize that on a clear day the sun's light is warm versus the cool blue tones bouncing in from the sky and therefore creates a cool-warm contrast, but I am not sure that I quite follow.

In the Bouguereau piece it seems that the girl is sitting outside in the shade and the soft light is being bounced around at least two walls of a light colored courtyard.

What am I missing? =)