Thursday, December 14, 2017

Judging Warm and Cool

Can you tell what colors are warm and cool in this scene?

At the beginning of my plein air painting workshops, I usually ask my students:  What problem would you like to work on most this week?  You might be surprised to learn that color temperature baffles many.  “I have trouble telling warm from cool” is something I hear often.

You're probably now saying:  “That's easy.  If it's yellow, it must be warm, and if it's blue, it must be cool.”  Well, yes, that's true in a macro sort of way.  We have this innate understanding because we associate yellow with fire and blue with ice.

But as most painters know, you can have cool and warm versions of a particular hue.  (I am considering a hue not to occupy a specific point on the color wheel but rather a pie-shaped region; in scientific terms, a hue isn't a specific wavelength of light but rather a range of wavelengths.)   Orange, for example, runs from yellow-orange to red-orange.  But how do you tell which of these two tertiary colors is warmest?

Context is vital.  You can't just say that yellow-orange is a cool or warm.  It depends on what color lies beside it.  Next to blue, yellow-orange appears so hot as to be incandescent.  But next to red-orange, it will appear cooler.

You can't look at isolated patches of your painting and say that this one over there is warmer (or cooler) than the one down here.  You have to place these patches right next to each other.   When I'm painting, I'll even place a dab of a mixture right on top of another to discern which is warmer.  I can easily wipe out or cover up this spot after I've rendered judgement.

Of course, this is all well and good when I'm actually applying paint.  But what if I'm observing my subject?  How can I judge the relative temperature of this bit of sunlit grass compared to the sunlit leaves on that tree over there, which may be feet—or miles—away?

The ViewCatcher

Experience helps.  But there's a tool that will aid you if you haven't developed the observational skills yet.  This is the ViewCatcher from The Color Wheel Company.   Many of us, including my students, are familiar with this tool as a compositional aid.  But there's another feature that many miss.  It's a little hole in the center of the slider.  Surrounding this hole is a square of mid-value, neutral-grey plastic.  By looking at a patch of landscape through this hole, you can gauge all four color properties of that patch:  hue, value and chroma, but also temperature.  Memorize the apparent temperature of one patch, then look at another—and you'll easily see if that second patch is warmer or cooler.

I've taken the same scene as above and have laid over it two (simulated) ViewCatchers.
You can see easily how the two color patches, though similar in value, are different in temperature.
The top one, which isolates the blue of the background hill, shows the blue as cool.
The bottom one, which isolates the shadowed side of a bare cliff, shows the shadow as a cool red--but
it is still warmer than the blue of the distant hill.

This process of memorization and analysis also takes some practice, but it's far easier than trying to compare temperature without it.  You can, of course, make your own “color isolator,” but the ViewCatcher is durable and can be stuffed into your paint kit without crushing.

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