1. Precautions for TAs Take control of the projector fan –Turn on the fan – don’t let students do this! –Turn off the fan only after the projectors cooled down. Announce that students: –should not control the fan at all –should dim projectors when not in use

2. Lab 14: Additive Color Mixing 1.Hue, Brightness (  intensity), Saturation (% white) 2.Calibration of Light Meters 3.White 4.Chromaticity Diagram or Color Triangle 5.Locating R, G, B on the Color Triangle 6.Adding Two Primaries: Blue and Green 7.Red Added to Green; Red Added to Blue 8.Complementary Hues 9.Color Matching 10.Matching Pigments 11.Spectral Colors – The Need for “Negative Intensities” 12.Are There Other Additive Primaries?

3. Caution keep the fan running all the time. –light bulb (500W) needs a continuous cooling dim/brighten slowly dim the projector when not in use

4. White Light Newton's dispersion experiment White light Color light

5. Real Spectrum UVIR = 570 nm (yellow) Light = Electromagnetic wave (nm) 400500600700 nm = 10 -9 m White light  a mixture of infinitely many wavelengths

6. Over-simplified Spectrum BGR 0 5 10 15 20 Type IType IIType III Sensitivity (arb. units) 400500600700 Sensitivity of cone cells  RGB primaries Additive primary colors: Red, Green and Blue

7. Color Triangle Any colors in the color triangle can be obtained by adding (i.e. overlapping light) RGB primaries 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g)

8. Color Triangle Fraction of red and green in the mixture determines the location of a mixed color 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g) (r, g) = (2/3, 1/3)

9. Adding R, G, and B Example: S = 100R + 50G + 0B Notation: S = aR + bG + cB 1.Total intensity of light I = (a + b + c) = (100 + 50 + 0) = 150 units 2.Fraction of each color r = g = b = Note: sum of fractions  r + g + b = 1

10. 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g) 100R + 50G r = 0.667, g = 0.333, b = 0 r = 0.667 g = 0.333 Orange

11. Adding R, G, B Example: S = 255R + 0G + 128B 1.total intensity of light I = (R + G + B) = (255 + 0 + 128) = 383 units 2.fraction of each color r = g = b =

12. 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g) 255R + 128B r = 0.67, g = 0, b = 0.33 r = 0.666 g = 0 Reddish Magenta

13. 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g) Mixed color lies on the line connecting two colors Mixing two colors Color Triangle Rule Fraction of colors  exact position

14. 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g) Any colors on a straight line from W: Same hue but increasing saturation Same Hue - Different Saturation Note: Purity = Saturation

15. 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g) Orange and Brown W and Gray R and less intense R Same Hue - Different Intensity Same (r, g)  Same location

16. Area of Human Color Vision Spectral colors lie along the edge of the horse shoe shape, outside of color triangle

17. 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g) W Y SY Complementary Colors SB Complementary color: SB & Y – equidistant from W Complementary hue: B & Y

18. References Image of dispersion by prism, (1994) http://www.exploratorium.edu/imagery/stills/Prism.jpg

19. Color Triangle 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 fraction of red (r) fraction of green (g)