1. Wavelength 1 produces a response of size X

2. Wavelength 2 produces a response of size X

3. The problem of “univariance”

4. So, we have a problem.

5. Here is a solution….add another cone type.

6. Two cones can give you color vision X/Y = red, X/Z = green COMPARISONS ARE CRITICAL

7. Three cones give you Trichromacy

8. Any light = aL + bM + cS

9. Let’s add some patches together

10. Let’s take GREEN

11. And add RED Red + Green = (M1+M2)/(L1+L2) = 1

12. Compare that to YELLOW Yellow = M3/L3 = 1

13. It follows that RED

14. RED plus GREEN

15. Yields Yellow R+G and Y are METAMERS This is ADDITIVE color mixture

16. But what about color paint in kindergarten? Blue paint Yellow paint

17. Mixing paint is SUBTRACTIVE The intersection of Blue paint and Yellow paint looks Green

18. Not all comparisons are used LWC - MWC gives you a red-green axis.

19. SWC - (LWC+MWC) gives you a blue-yellow axis.

20. Gray Everything is balanced

21. “unique” yellow

22. “unique” green

23. Purple… A “non-spectral” hue

24. Recall…Three cones give you Trichromacy Suppose: if S=M=L, then WHITE

25. Suppose that L gets tired? What does S=M>L look like?

26. Boring

27. Stare at the center

28. Boring?

29. Pretty boring……

30. Try this Negative afterimage