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120R+G+B vs. gray, LCD projector

More depth on Gamma

• Poynton, Gamma and its disguises: The nonlinear mappings of intensity in perception, CRTs, film and video. SMPTE Journal, 1993, 1099-1108

Halftoning

• The problem with ink: it’s opaque

• Screening: luminance range is accomplished by printing with dots of varying size. Collections of big dots appear dark, small dots appear light.

• % of area covered gives darkness.

Halftoning references

• A commercial but good set of tutorials• Digital Halftoning, by Robert Ulichney,

MIT Press, 1987

• Stochastic halftoning

Color halftoning

• Needs screens at different angles to avoid moire

• Needs differential color weighting due to nonlinear visual color response and spatial frequency dependencies.

Halftone ink

• May not always be opaque• Three inks can give 2^3=8 distinct colors• Visual system gives more since dot size,

spacing, yields intensity, gives somewhat additive system

• Highly nonlinear. See Berns et al. The Spectral Modeling of Large Format Ink Jet Printers

From http://www.matrixcolor.com/

108° 162°

90° 45°