1. Remember anableps, the 4-eyed fish? It has two visual systems in a single eye, for seeing both above and below the waterline. What is the duplex retina? What is the evidence for having a duplex retina? How should we think about having a duplex retina? Are we like the anableps?

2. Be able to diagram and explain the relationship between radiance, illuminance, luminance, reflectance, and brightness. Can I predict the amount of brightness if I know how much light energy is coming from an object? Explain why or why not.

3. In discussions about brightness, I said that the rule is "the coal is always black." Using two objects, like a piece of coal and my white-if-it-was-clean coffee cup, explain what this statement means with respect to illuminance, luminance, and reflectance. Is it an illusion or is it real that the coal is always black?

4. Explain the simultaneous contrast illusion. Does this illusion contradict or support the concept of brightness constancy? Is it an illusion or is it real?

5. What are Mach bands? Are Mach bands real or are they illusions?

6. Explain the concept of "lateral inhibition." Draw and explain a retinal circuit that shows how lateral inhibition could produce Mach bands.

7. Draw a portion of a Hermann grid. Explain the illusion seen. Explain the illusion according to a lateral inhibition explanation. Where is the illusion? Is what we see real or an illusion?

8. What is the meaning of the difference between the layout of the color circle and the spectrum? Why is purple considered such an important color?

9. Explain how additive and subtractive color mixing work in daily life. Explain how to make my coffe cup look purple, using additive and subtractive color mixing.

10. Explain how the Munsell system works. Explain how the CIE color system works.

11. If you could only use one of the two color systems, which one would you use? Explain why.

12. Explain the development of trichromatic theory. What did Helmholtz do? What did he find?

13. Explain the development of opponent process theory. What did Hering consider to be the critical evidence supporting his hypothetical color receptors?

14. Be able to draw and interpret the spectral sensitivity curves for the three types of cone receptors in humans. What are the "primary" colors according to the cones? Does this contradict our tendency to talk about red, yellow, green, and blue as being primary colors?

15. How does trichromatic theory and opponent process theory explain seeing colors like purple, cyan, and yellow?

16. Describe the three types of color blindness. Pick your favorite type of color blindness and explain what happens to the color world of that individual. Predict what should happen if we discovered that some people had a fourth type of cone. How could we discover these people?

17. Why should we label the cones as S, M, & L wavelength instead of the colors, Blue, Green, and Red?