Wednesday, February 17, 2010

Light and Form, Part 2

Within the shadow is not darkness but the effect of other, weaker sources.

In the case of the drapery study above, drawn in graphite while I was in art school, the key light strikes the form from the left. You can tell it’s a hard source because of the sharp diagonal cast shadow line. Overhead fluorescents, only slightly less bright, illuminate the shadow side.

The drapery study has the look of an academic exercise partly because it is "overmodeled" which means the tendency to put the full range of modeling factors within each passage.

Outdoors, the blue light from the sky usually modifies the shadow planes, depending on how much they face upward. Reflected light often raises the tone of the shadow. It comes from light bouncing up off the ground surface or from other surfaces. The darkest parts of the shadow are usually at points of contact, called occlusion shadows, where secondary sources can't reach.

Another dark part of the shadow is the area just beyond the terminator. This area is called the core or the hump of the shadow. The core of the shadow only forms if the secondary source of light (edge light, reflected light, or fill light) doesn’t overlap too much with the main light.


In “Daniel in the Lion’s Den,” by Rubens, a strong orange-colored reflected light fills the shadow side of Daniel’s form, all the way from his cheek and neck, down his arm and his leg. Keeping the core intact—or painting it in even if it’s not really there—can give the form more impact, but if it’s overdone it can look unnatural.

If you’re setting up a model or maquette, you can place the primary and secondary lights just far enough apart so that you can see the core beginning to form.

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

8 comments:

Dan Gurney said...

"Within the shadow is not darkness but the effect of other, weaker sources."

Sounds almost Jungian.

Until you pointed it out to me some years ago now, I was not aware of all the colors that appear in shadows. I see them now.

Thanks!

James Gurney said...

Hey, Dan, Those other sources really become apparent when you switch off the main light or the sun goes behind a cloud.

What I find amazing is that the blue light in outdoor shadows was not consistently observed by anyone (well, maybe by daVinci and a few others) until well into the 19th century.

The Pre-Raphaelites were pioneers in rendering blue sky light in shadows, a few decades before the Impressionists, and they took a lot of criticism for it, because it didn't look like the brown shadows people were used to.

Mary Bullock said...

I love draped fabric - the folds, the zigzags, the shadows, etc. You did a great job! Mucha was so good at this too.

Torbjörn Källström said...

Hehe, yes. It was quite a revelation for me to realize that shadows are actually blue on sunny days. It's kind of strange to never have noticed before.

DavidStill said...

My opinion is that no-one did really good landscapes until the 19th century... There are, of course, exceptions.

Don Cox said...

"What I find amazing is that the blue light in outdoor shadows was not consistently observed by anyone until well into the 19th century."

Especially as they knew about blue in the distance centuries earlier - Breughel, for instance. Maybe it's because they did all their painting indoors.

I wonder what other major effects there are that nobody has yet noticed.

Jared Shear said...

Thank you once again for another exciting bit of info on light......much appreciated!

greyskyeyes said...

Great article! I really appreciate this series. It's always really good to have an understanding of how to interpret light and form.

Your timing is excellent for me as my 15 yr. old daughter is covering a unit on this in her honors art class. Their assignment last night was to render a ball five times with different light sources. Part 1 of this series really helped her get the gist of what it's all about.
Thanks!
(PS. We recently visited the NGA in DC and got to see Reubens'“Daniel in the Lion’s Den” in person.)