Credits and Inspiration Credits and Inspiration:

First things first: I would like to mention three things that inspired me to create Features of Light and Darkness. If it weren't for all of them, the app would not exist.

It started literally at my mother's knee. Ruth Freeman was an architect who specialized in the design and aesthetics of building interiors. There was a green color that was popular for interior walls, that could be prepared in two ways by the painters. They could add green pigment to white base paint, or add smaller amounts of blue pigment and yellow pigment. The results looked identical in daylight: They were both a soft blue-green. Yet my mother always specified that the paint be mixed the first way, because she knew that under artificial lighting by the rather "cool" fluorescent lights in use at the time, the green made with blue and yellow pigments looked different from the green made with green pigment. As a child, I had no idea why that was so, and I don't think she did either, but she could tell the difference, and so could I.

Second, when I was an undergraduate at the California Institute of Technology, I got to see physics Nobel Laureate Richard P. Feynman present his celebrated lecture on color vision. Feynman worked with sets of colored theatrical spotlights aimed to overlap on a screen, to produce several kinds of light side by side. He would pass pieces of poster-board coated with pigments through the light beams to present various effects. The display was dazzling, and Feynman's showmanship was superb. The basic idea of Features of Light and Darkness, as well as several of the built-in scenes, was inspired by the demonstrations in that lecture.

Finally, the name "Features of Light and Darkness" is word-play on Creatures of Light and Darkness, which is the title of a book by the late science-fiction and fantasy author Roger Zelazny. The book has nothing to do with the technical details of color vision, but I happened to have it in mind when I started thinking about the program. Zelazny was a great author, and I recommend all of his works, not only Creatures of Light and Darkness.

In addition to specific credits for inspiration, I must thank Apple for providing the excellent software that I used to develop Features of Light and Darkness, and for many good examples of how to use it. I must also acknowledge that any flaws or failures in this app are my fault alone; please let me hear from you when you find any, at