Tuesday, June 26, 2012

A White Building in Shadow

Quick question: What color would you mix for the shadow side of a white building on a sunny day with a clear blue sky?

I probably would have answered "cool gray," but I would have been wrong. 


In fact, all the swatches above are from the shadow side of the same building from a single photo. They range from dark green to pink to gray. It's hard to imagine mixing those colors and making them look right.

Did any of you answer "It depends?" If so, you had the right answer.

So what does it depend on? For one thing, the shadow side depends on the color of the sky. It's bound to pick up some of the blue color from there. But the reflected light from adjacent surfaces can be a huge influence, too.

If the reflected light is powerful enough, it can be the dominant factor.


In the photo above, you can see where the four swatches came from. The first swatch came from the top of the near plane. It's greenish because it's getting blue skylight plus green reflected light from the grass. That pink swatch is getting red-orange reflected light combined with blue light. Swatch #3 is lightened considerably by the white reflected light. 


And area #4 is slightly more yellow-green than #1 because it's got a wider zone of grass reflecting into it. Here the limits of the camera's sensitivity fails us. The human eye is far more sensitive than the camera, and if you were observing and painting the scene, you'd see and paint these differences even more dramatically.
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Read more about vertical surfaces in shadow in my book Color and Light: A Guide for the Realist Painter.


Previous posts: 
Downfacing planes
Vertical planes in shadow
A whitewashed wall in shadow

11 comments:

Janet Oliver said...

Very helpful, thank you James.

Laura said...

Better color acuity: Yet another reason to paint outside. :)

ChristineMM said...

I thought I was decent at photography and thought 1 photo could do the trick but after trying to learn watercolor and to see color, when taking photos I realized the pitfalls of the camera that i didn't see before. Now I have just right foreground and overexposed sky or just right sky and dark foreground or other challenges. I started taking lots of photos with multiple exposures in order to try to remember the scene for later. I finally realized how the human eye in nature sees more color all at once than the camera can ever capture.

(Did you ever wonder about dog and cat's eyes and how they perceive our world differently colored or different brightnesses?)

Richard said...

When I was teaching my very young children colors, I once showed them a white wall and asked what color it was. One said "yellow" and the other, standing a little distance away, said "green". At first I was a little worried about them until I realized they were right. There were very strong reflections on the wall. The bizarre thing was I had to somehow teach them the right answer, at least in school, was "white".

Richard

Mark Heng said...

I'm struck by how red the underside of the slats are on the reddish swatch. If I was making it up, I would have assumed they would be much lower in saturation, maybe even blueish...Guess not!

Alan said...

Richard's comment reminds me of Harry Chapin's song "Flowers are Red"... and also the TED talk with Ken Robinson "Do Schools Kill Creativity?"

It's interesting how we as adults force-feed the "well-meaning" accepted view onto our kids.

Zoe said...

Thank you James, your posts and advice about color and light are always wonderful! :)

Dan Kent said...

Love this. When I was a boy I remember thinking that shadows had color. I am validated, er, a few years later. :)

Tom Hopp said...

Absolutely fascinating, James. Thanks.

António Araújo said...

Alan, schools don't kill creativity, lousy teachers do. :)

The fact that shadows are (usually) colored is a pretty immediate consequence of basic optics, although it was, historically, a big "discovery" in art - but it wasn't so much a discovery of the fact as a decision to pay attention to said fact, and therefore to paint it.

In fact you could calculate the (local) color of each point in the shot by specifying the spectrum of the main light source and the reflectivity of each surface in the environment.

A good teacher of physics might choose to point that out in class to make a connection with art - and a good teacher of art might point to the basic physics to make the reverse connection; alas, few will choose to do so.

However, "shadows are colored" is a slogan, and as such it points to a truth but it is also misleading.

It isn't so much that shadows have color, it is simply that what is in the shadow of a colored light source is being lit by another (secondary) colored light source.

The thing to remember is that every bit of surface that receives light becomes itself a (secondary) light source. Light coming out is light coming out, it doesn't care if it comes from a nuclear reaction in the sun or from a reflection from a roof tile - both are light sources and hence will light other stuff.

But it also follows that without secondary light sources, shadows will not be colored.

In fact, if you take a ball, put it in a vacuum, and lit it only from one side, the shadow side will just be black. You can see this in, say, the shot of a moon. The shadow side, under the right conditions, is invisible against the black background. Shadows are not colored in themselves.

But once you put other elements in the shot, you get "colored shadows". All it takes is a back wall behind that ball in the studio, or even an atmosphere around that planet and you'll get reflected light in the first case, and scattered light in the second case, and the shadow side will be lit.

The most important point may be that the expression "shadow side" has no meaning except in relation to a *specific* light source.

António Araújo said...

Alan, schools don't kill creativity, lousy teachers do. :)

The fact that shadows are (usually) colored is a pretty immediate consequence of basic optics, although it was, historically, a big "discovery" in art - but it wasn't so much a discovery of the fact as a decision to pay attention to said fact, and therefore to paint it.

In fact you could calculate the (local) color of each point in the shot by specifying the spectrum of the main light source and the reflectivity of each surface in the environment.

A good teacher of physics might choose to point that out in class to make a connection with art - and a good teacher of art might point to the basic physics to make the reverse connection; alas, few will choose to do so.

However, "shadows are colored" is a slogan, and as such it points to a truth but it is also misleading.

It isn't so much that shadows have color, it is simply that what is in the shadow of a colored light source is being lit by another (secondary) colored light source.

The thing to remember is that every bit of surface that receives light becomes itself a (secondary) light source. Light coming out is light coming out, it doesn't care if it comes from a nuclear reaction in the sun or from a reflection from a roof tile - both are light sources and hence will light other stuff.

But it also follows that without secondary light sources, shadows will not be colored.

In fact, if you take a ball, put it in a vacuum, and lit it only from one side, the shadow side will just be black. You can see this in, say, the shot of a moon. The shadow side, under the right conditions, is invisible against the black background. Shadows are not colored in themselves.

But once you put other elements in the shot, you get "colored shadows". All it takes is a back wall behind that ball in the studio, or even an atmosphere around that planet and you'll get reflected light in the first case, and scattered light in the second case, and the shadow side will be lit.

The most important point may be that the expression "shadow side" has no meaning except in relation to a *specific* light source.