non Green really complements non Red (sort of)

By Roy Zuniga

In previous posts I confirmed my initial thesis that the traditional colors artists consider as complements (Red/Green, Orange/Blue and Yellow/Violet) are not actually complements in the pure color space of the computer. I showed how none of the colors that are 180 degrees apart in the HSB color space align with the artist’s complements. And we saw how the computer complements actually do neutralize each other. So in a purist sense, is the computer right and artistic color is wrong?

Wait a minute, aren’t artists by definition color experts? How could they be so off? I postulated that this may be due to a number of factors, including color shift (the illusion that colors shift hue as they are tinted), and the colors available to artists (which are not as saturated or bright as what you can show on a screen). For example, the chart below shows how fully saturated, bright colors (center stripe) tend to shift in hue as they are tinted white (top) or black (bottom).

You’ll notice that yellow looks decidedly greenish as it is tinted toward black, even though the hue number doesn’t change. The computer tells us that both the saturated color in the middle and the one close to black in the yellow band are in fact the same number (60). What changed is the brightness; saturation was maintained constant at 100%.

Other colors play similar tricks on our eyes: orange looks redder as it gets darker, magenta shifts into violet, and violet tugs at blue in the darker tones. Cyan lists toward green and green warms up considerably in the darks. In the lights, orange and green both look yellow; and a few of the lights in the red to violet range seem identical to the untrained eye; same for the blue greens. What appear as 12 distinct colors in the saturated range become about 5 or 6 distinguishable colors as they approach white or black.

How does all this account for the gap between tradition and the algorithmic complements? I decided to do a little experiment, which is very subjective by nature. What follows is not a proof; it’s a plausible explanation at best.

First, I selected typical artist colors for main colors, red, orange, yellow, green, blue and violet (Viridian, Cad Red, Cad Yellow, Cobalt Blue, etc.) Since various manufacturers produce paints that look different even though they have the same name, this is an inherently subjective exercise. I squirted out a few and got an optical range to work with. I adjusted the ‘pure’ colors in my color calibrated monitor to more or less match the blotches on the white canvass paper. In other words, I created my equivalent of an artist’s red, orange, yellow, green, blue and violet on the computer, and used the same blending feature to blend these adjusted colors along the traditional pairings.

The result was quite interesting. When I examined the hue number for my adjustments, it turned out some had shifted. For example, pure yellow is #60, while my eyeball artist’s yellow is #56; orange went from #30 to #32 (no big deal there); Red didn’t shift hue at all and neither did blue; green leaped by nine from #120 to #129; and violet went up 8 ticks from #270 to #278. The Red/Green duo grabbed my attention next, since there seemed to be convergence to more closely align with the computer complements. I decided to push the envelope to see if the would converge further.

Using the same blend tool and applied to my ‘artist’ colors, blue was mixed with green and violet with red to get some intermediate colors. Sure enough, I found I could accept colors that were closer to my target 180 degrees of opposition. I picked two new colors, as shown here.

Re-running the blend, the result was a further narrowing of the gap, showing how from the artist perspective, red and green can be loosely considered complements. My optical green lost 60% of it’s brightness from the pure green. As we saw above, that would have shifted its appearance towards red. So to compensate, the hue was moved towards blue. Red, as it loses brightness definitely pulls towards orange. To compensate I instinctively adjusted toward violet. Consequently, the two converged. The blended colors you see below are not true red and green according to the computer. Ask any artist, however, and she will likely say they are red and green – and perception is everything!

Since these mislabeled colors are very close to the true computer complements, it is plausible that empirically colorists did see them neutralizing each other in the past (you now know better, of course). Thus the ‘artist’ adjusted colors are only 23 degrees off the 180 degree opposition required to be true complements. This is much less than the 60 degrees departure we see in the pure saturated version of green and red. In other words, in the pure computer model, red (#360) is two complement bands away from green (#120). In the optically adjusted model, we can get away with saying they are less than one band away – and in the fuzzy world of mixing pigments, the distinction may be academic. Thus we account for the origin of the myth that red and green are complements! The colors known as red and green behave closely to how complements behave, i.e. neutralizing each other. 

Some lessons we can take away include:

1. A plausible explanation of how the classical complements model was conceived as colorists mixed pigments they had at hand.
2. An understanding that if we want to neutralize colors with their true complements, we have a new chart to look at and pick from.

copyright 2009 roy zuniga