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Announcements 4/9/12

Announcements 4/9/12. Prayer HW 25 due on Tuesday HW 26 due on Wednesday (but it’s very likely Claira won’t pick it up until Thursday night. Shhh!). Frank & Ernest. Reading Quiz. How many types of cone cells are there in humans? 1 2 3 4 5. Reading Quiz.

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Announcements 4/9/12

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  1. Announcements 4/9/12 • Prayer • HW 25 due on Tuesday • HW 26 due on Wednesday (but it’s very likely Claira won’t pick it up until Thursday night. Shhh!) Frank & Ernest

  2. Reading Quiz • How many types of cone cells are there in humans? • 1 • 2 • 3 • 4 • 5

  3. Reading Quiz • The functions r(l), g(l), and b(l) are called the: • color adding functions • color displaying functions • color matching functions • color realizing • color subtracting functions

  4. The Goal

  5. Visible Spectrum • “All the colors of the rainbow…”  Where is brown?? • What’s a “luminescence spectrum” that you might measure? From Wikipedia, “Visible Spectrum”

  6. Cone cells • “Short” • “Medium” • “Long” From Wikipedia, “Color Vision”

  7. Color blindness Test for tritanopia Test for deuteranopia • tritanomaly – S cones mutated (rare) • tritanopia – lacks S cones (<1% of males) • deuteranopia – lacks M cones (1% of males) • deuteranomaly – M cones mutated (6% of males; 0.4% of females) • protanomaly – L cones mutated (1% of males) • protanopia – lacks L cones (don’t know %) From Wikipedia, “Color Blindness”

  8. Primary Colors • How the primary song should go • “Additive color mixing” – demos • Subtractive colors - demo From Wikipedia, “RGB Color Model”

  9. Components of R, G, B • Plot 3 components in 3D “color space” From Wikipedia, “RGB Color Model”

  10. What are R, G, B? • The spectra of R, G, and B phosphors from a standard CRT (i.e. non LCD) computer monitor • Could also, e.g., have R = sharp peak at 635 nm, G = sharp peak at 532 nm, B = sharp peak at 447 From Wikipedia, “Primary Color”

  11. A Problem • R = sharp 635 nm, G = sharp 532 nm, B = sharp 447 nm • What happens if you want to get, say, orange = 580 nm. Can you mix R, G and B to get this? • 532 nm will excite some S! • 580 nm alone will never excite S!

  12. 1920’s Experiments red source = 700 nm green source = 546.1 nm blue source = 435.8 nm • Important results: • Human eye response can (mostly) be described by 3 parameters • Human eye response is (mostly) linear to get 580 nm orange, need some “negative” blue From Wikipedia, “1931 Color Space” (also in P&W)

  13. What is a “Color Space”? • How strong of r, g, and b, lights would you need to match a light that is not a delta function? • Compare: what would you get for the response of a detector that has, say, g-bar as its response curve?

  14. 1931 Color Matching Functions From Wikipedia, “CIE 1931 Color Space” Human eye response again • Properties of these functions: • all are positive • z-bar = very close to S cones, very close to previous b-bar • y-bar = matches intensity response of eye, very close to M cones • x-bar = chosen so that white is equal parts x-bar, y-bar, z-bar

  15. 1931 Color Matching Functions etc. etc.

  16. Worked Example • X = • Y = • Z = Normalize (because “color” should not depend on overall intensity) • x = • y = • z =

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