2. Printer/monitor incompatibilities Gamut –Colors in one that are not in the other –Different whitepoint –Complements of one not in the other Luminance ranges have different quantization (especially gray)

3. Photography, Painting Photo printing is via filters. Really multiplicative (e.g..2 x.2 =.04) but convention is to take logarithm and regard as subtractive. Oil paint mixing is additive, water color is subtractive.

4. Printing Inks are subtractive –Cyan (white - red) –Magenta (white - green) –Yellow (white - blue) In practice inks are opaque, so can’t do mixing like oil paints. May use black ink on economic and physical grounds

5. 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.

7. Halftoning references A commercial but good set of tutorials Digital Halftoning, by Robert Ulichney, MIT Press, 1987Digital Halftoning Stochastic halftoning

8. Color halftoning Needs screens at different angles to avoid moire Needs differential color weighting due to nonlinear visual color response and spatial frequency dependencies.