Eye training: discriminating value

Dick Nelson has started a new round of his 10-week color class, "Interaction of Color", based on his training with Josef Albers. The students are Maui artists in a variety of media. I volunteered to be his assistant, so I "drive" the computer during demonstrations, and he has me review and comment on his assignment handouts to make sure they're as clear as possible.

In the first class, one of the "discovery" exercises was to sort a set of black, white, and gray strips into an array of equal steps. (See this post on arrays.) The idea is for the value change between pairs to be even, as the distance between stair steps is even.

We are using Adobe Illustrator for this class. It has a function called "blend" which will create intermediate colors between two objects. This can be a smooth gradient blend, or discrete steps, which is what we are using. Illustrator appears to use a linear interpolation to create its blends. We don't perceive the resulting steps as being visually equal. (We'll go into the technical explanation of that later in the course.) He wanted to make a point of this, so we will learn to trust our own eyes, and make our own judgments, not just trust the computer results "blindly".

The arrays at the top of this post illustrate the difference. The top array was produced by the blend function in Illustrator. I built the values in the second one by repeatedly finding the middle value between two extremes. The differences are most pronounced at either end. Looking at the top row, at the light end, the jump from white to the first gray produced by Illustrator is too great. We can imagine a large number of intermediate grays. Then the difference from the second to third does not "feel" as large as from the first to the second. Similarly, at the dark end of the Illustrator row, the final gray is almost black, so that feels like a small step, while the step leading up to it feels larger. In my array, on the bottom, the steps from one value to the next seem more even, so if you were walking up them, you wouldn't stumble.

If you click on the image to see the large version, you may notice an interesting phenomenon when you look at individual gray strips. They appear to have a fluted appearance, as if each rectangle had a gradient, from left to right, of darker to lighter gray. But each is a single, solid shade of gray, which you can prove to yourself if you block off its neighbors. This phenomenon has to do with how we perceive. What we see depends on the context.

The whole point of the class is to increase our awareness of, and sensitivity to, the facts of our visual perception, so we can use that knowledge to create the effects we want.