Thursday, July 18, 2019

Master Class: How to Determine the Color of a Light Source

I can't really tell what the color of the light source is here, but
I can definitely see a blue-violet cast to the shadows within the folds.
So, I'm going to assume the light is the complement, or yellow-orange.
Of course, blue skylight bouncing down into the shadow also
colors the shadow.

"First, determine the color of your light source."  This piece of advice often is shared with painters when they are striving to paint correctly the color relationships of light and shadow areas of an object.  Knowing the color of the light source helps you decide how warm or cool to paint illuminated areas, and consequently, how to paint the shadowed areas.

So how do you determine the light source color?  I must credit Doug Dawson, my friend, fellow painter and art instructor, with this idea.  Take a sheet of white paper, crumple it up, and toss it into the light.  But rather than look at the lit areas of the paper for clues, look into the pockets of shadow.  It's easier to determine the color of shadow than of light.  Once you've determined the shadow color, you can assume that the light will be its complement.

For example, if you see the shadow as a pure blue-violet—often the case on a sunny day with clear air—you can assume the light will be a yellow-orange.  On a cloudy day, the shadow will be lighter and warmer because of the diffused light, which makes the shadow color somewhat harder to gauge.  I sometimes read this as a grey with a slight red bias, which would indicate that the light has a greenish quality.

Finally—and this is my own advice to students—if you can't determine the color of the light, just make a decision.  If you waffle, your light/shadow relationships are likely to be confused, and this will also confuse your viewer.

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