Lab 14 Additive Color Mixing 1 2 3

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

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

White Light Newton's dispersion experiment Color light White light

Real Spectrum UV l(nm) 400 IR 500 600 700 nm = 10 -9 m l = 570 nm (yellow) Light = Electromagnetic wave White light a mixture of infinitely many wavelengths

Sensitivity (arb. units) Over-simplified Spectrum 20 15 Type III 10 5 0 400 500 B 600 G 700 R Additive primary colors: Red, Green and Blue Sensitivity of cone cells RGB primaries

$Color Triangle fraction of green (g) 1 Any colors in the color triangle can$

Color Triangle fraction of green (g) 1 Any colors in the color triangle can be obtained by adding (i. e. overlapping light) RGB primaries 0. 8 0. 6 0. 4 0. 2 0 0 0. 2 0. 4 0. 6 0. 8 fraction of red (r) 1

$Color Triangle fraction of green (g) 1 Fraction of red and green in the$

Color Triangle fraction of green (g) 1 Fraction of red and green in the mixture determines the location of a mixed color 0. 8 0. 6 0. 4 (r, g) = (2/3, 1/3) 0. 2 0 0 0. 2 0. 4 0. 6 0. 8 fraction of red (r) 1

Adding R, G, and B Example: S = 100 R + 50 G + 0 B Notation: S = a. R + b. G + c. B 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

100 R + 50 G r = 0. 667, g = 0. 333, b = 0 fraction of green (g) 1 0. 8 r = 0. 667 0. 6 Orange 0. 4 g = 0. 333 0. 2 0 0 0. 2 0. 4 0. 6 0. 8 fraction of red (r) 1

$fraction of green (g) 1 Color Triangle Rule Mixing two colors 0. 8 Mixed$

fraction of green (g) 1 Color Triangle Rule Mixing two colors 0. 8 Mixed color lies on the line connecting two colors 0. 6 Fraction of colors exact position 0. 4 0. 2 0 0 0. 2 0. 4 0. 6 0. 8 fraction of red (r) 1