Tuesday, May 20, 2008

Color Theory: Q & A

Dear Rebecca, those were not dumb questions even if you knew lots about color theory. In fact, it's taken me all day to research the answers for you.

Q: Why is the completed color chart left with empty spaces? It seems like you could certainly have colors that continue on all the rows (except maybe the bottom, which looks pretty much like black).

A: I totally thought the same thing when I first saw the color charts! That was the big question that I focused on when I started reading the text. Luckily, the text addresses this issue in the first chapter. (Then I moved on to trying to understand why Munsell insists that chroma and saturation are not the same thing, which is a question for another day.)

First, the Munsell color system is based on the color gamut (all the possible variations in hue, value, and chroma that can be achieved in a medium) of opaque paint. So the number of possible chips is limited to the 1,300 or so colors which can be made with pigments available in opaque paint today.

The completed color chart has empty spaces because hue families do not contain the same number of colors. Hues have varying numbers of values. For example, yellow is a light color with a large number of uniform steps between it and gray. So the yellow chart has more chips in the top rows and fewer chips in the bottom rows. Conversely, purple is a dark color. So the purple chart has more chips in the bottom rows and fewer chips in the top rows. Hues also have different numbers of steps of chroma. For example, more steps of chroma are possible for reds than for blue-greens. Reds reach a chroma of /16. This means there are 16 perceptually equal steps between a gray paint and the most intense red paint. A blue-green, however, reaches a chroma of only /10. In other words there are only ten equal steps between the purest blue-green that can be made with paints and a gray. Therefore, although reds and blue-greens reach their highest chroma at the same value level, they do not bulge out the same amount from the gray scale.

So your observation about the lowest row on the red chart is spot on: it pretty much looks like black. At the darkest value of red which is perceptually discernable from black there are no more variations in chroma possible. That’s as red as red-black can get. And that’s as black as red-black can get. Imagine you were mixing paint. If you added red to that color it would increase the value and push it up to the next row. If you added black to that color it would be black.

Finally, The New Munsell (R) Student Color Set (2nd ed.) provides only a representative sample of the ten basic hue families. The large Munsell Book of Color includes all of the 1,300 or so colors available in the color gamut of opaque matte paint. For example, The Munsell Book of Color includes all 16 steps of chroma on its red chart and all 10 steps of chroma on its blue-green chart, while The New Munsell (R) Student Color Set (2nd ed.) reaches only /14 on the red chart and /8 on the blue-green chart.

Q: Do those colors (from the blank spaces on the hue chart) show up on another chart?

A: No, not really. Imagine you were that red-black on the bottom row of the red chart. As we discussed above, if you were redder, you’d be one of the colors on the row above. If you were blacker, you’d be black. If you had another color added to you, for simplicity’s sake let’s say blue, then you’d be on the purple chart. But no matter what happens to you, you won't land in one of those blank spots on the red chart. So there’s nothing that goes in those blank spaces, at least within the current color gamut of opaque matte paint.

Q: Do the charts fit together?

A: Yes. The far left column on each chart is the value scale from black to white. If you stood the charts up and arranged them in a circle around the color wheel with their gray scales toward the center, you would have a rough approximation of the Munsell Color Solid. In fact, you can buy just such a thing: The Munsell Color Tree, pictured at left.




As each color has three dimensions, hue, value, and chroma, all of the colors can be arranged into a three dimensional form. Due to the variations in the numbers of values and chromas among the hues, the shape of the Munsell Color Solid is likened to a wonky citrus fruit.

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3 comments:

Rebecca said...

Wow. Who knew color could be so complicated? (I admit I mocked your choice of Christmas gift a bit.) I have to digest all this information and I'm sure I will have more questions that I can't quite articulate at this moment.

I will say that I feel like a complete math nerd because the first thing I thought of when I saw the wheel at the end was 'what a cool application of cylindrical coordinates'!

Thalia said...

This is only slightly related to the post, but Sarah - I don't have your e-mail at the mo, and I wanted you to see this quilt (or part of), just in case you, you know, wanted to make something like it.

http://www.flickr.com/photos/needleloca/2468575447/in/set-72157604904666637/

Sarah said...

Dear Rebecca,
I was equally surprised to learn of the complexity of color theory, but it's pretty cool once you get into it. The Munsell color system is especially math nerd friendly. It's all about the numbers. I'll post more about its mathitude another day.

Dear Thalia,
So do I hear a subtle suggestion that you'd like me to make you a quilt like this, mi tortogita? I'll add the Tortogita Quilt to the long list of quilts in various stages of production. Mind you, Rebecca's got two in the queue already which have been called on account of innumerable friends' babies' quilts. I advise against breath holding.