------------------------------------------------------------------------------- CS 99D - Color #1 - March 1, 2001 Marc Levoy Stanford University (c) 2001 (with corrections, March 14, 2003) ------------------------------------------------------------------------------- *** Color theories: Aristotle through 1800 *** (from Kemp) 384-22B Aristotle De sensu et sensibili ("On sense and sensible objects") and De coloribus ("On colors") o 7 colors: white, yellow, red, purple, green, blue, black o colors can be arranged on a scale from white to black o most pleasing colors match (in brightness) grayscale tones that contain black and white in ratios of whole numbers, e.g. 3:2 or 4:3 o inspired by the mathematical structure of musical scales o this intimate association of hue and tone persisted until well after the Newtonian revolution, until the 19th century (Kemp, p. 264) o 3 ways to mix colors 1. adjacency (of small patches) 2. layering (of semi-transparent layers) 3. mixing (of substances) 1452-19 Leonardo On painting o 6 colors: white, yellow, red, green, blue, black o corresponding to: earth, fire, water, sky o complementary colors: o red "enhances" green o blue enhances yellow o mixtures of colored lights: o blue + yellow = green o wrong for light! probably just a thought experiment (o might be correct, depending on spectrum of yellow) o many observations on perception that he couldn't explain o we see tones but no colors in a dim environment (Leonardo, p. 73) o due to scotopic vision o a colored surface in a medium-dim environment loses its color when viewed through an aperture from a bright room (p. 74) o due to adaptation, but still not clear 1584 Giovanni Lomazzo Symbolic and astrological color theories -> Temple of Painting, Kemp, p. 271 o relationship of color to other aspects of painting o associations between colors and: o astrological signs o virtues o temperaments o seasons o metals o religious characters o white = pure, red = ardent, purple = imperial, blue = virgin 1613 Francois d'Aguilonius's De lumine et colore (w. Peter Paul Rubens) Color scales versus color mixtures -> Aguilonius's simple and composite colors, Kemp, p. 275 o correct description of subtractive mixturing effects o no understanding of underlying cause o color scale is still arbitrary 1577-40 Peter Paul Rubens o "colors should not be tormented" o mix no more than two on the palette (subtractive) o further mixtures should occur in the eye (additive) o cangianti: hue shifts between lit and shadowed areas, known since Cennini -> Mantegna's Madonna and Child... (1495), Kemp, p. 323 -> Ruben's Blessings of Peace (1630), Kemp, p. 277 and detail on p. 326 o "shadows should be kept translucent" o neutral glazes to darken underlying color o "highlights should be opaque and pure" o these are instructions on artistic technique, but o the need for a scientific understanding tormented them 1666 Newton Optiks (1704) o demonstration of decomposition of white light into colors o demonstration of mixing of colored lights to re-form white o closed figure provided a geometric method for additive mixing -> Newton's color circle, Kemp, p. 286 o spacing determined empirically by mixtures, and by o color + complement (opposite on circle) = white, and o by proposed corresponding musical notes, as shown o confirmed difference between additive and subtractive mixing o mixing dissolved dyes -versus- mixing dye powders ...but... o couldn't explain hues from additive mixing versus spectrum o R + G = yellow -versus- yellow spectral light o R + G + B = white -versus- sum(all wavelengths) o i.e. couldn't explain our perception of hues ...so... o couldn't say how many primaries are needed to form all colors o couldn't say what colors those primaries should be, in fact o couldn't argue that the primaries should be spectral colors ==> Demonstrate R + G + B light through colored slides ~1720 Jakob le Blon 3-color printing process o demonstration of subtractive mixing -> Blon's 3-color printing process, Kemp, p. 328 o proof that three primaries suffice to reproduce any color o three primaries for printing are C,M,Y ==> Demonstrate W - C - M - Y light through filters Questions about these two demonstrations: o With a prism, one can analyze le Blon's colors to determine that they are each wide spectral bands. o It is obvious that filters are subtractively mixing. o With these facts, one can explain why W - C - Y = G o But, with a prism, one can create narrow R,G colors, which when mixed additively give R + G = Y, but their plots, when added, don't include spectral yellow. o Can't explain the existence of magenta at all. -> Additive versus subtractive color mixing 1754 Louis Bertrand Castel Color and music o Jesuit priest, "scientist", and polemicist o "occular clavichord" o some (Huygens) theorized that both were due to vibrations o such correlations had led to many discoveries (Kepler,...) 1772 Johann Lambert 3-dimensional colorspace -> Color pyramid, Kemp, p. 290 o mixtures of 3 primaries on each plane o black at center of base plane o tones up to white o 3-dimensional figure, not 2 o less color discrimination among high tones o also less color discrimination among low tones, but this fact is hidden in this representation 1742 Comte de Buffon Complementary colors o scientist at the French Academy of Sciences o also father of geometric probability - Buffon's needle o observations of after-images o after-image color is painter's "complementary color"! o color and after-image are opposite on Newton's color circle! 1810 Philipp Runge 3-coordinate color system o artist and writer -> Color sphere, Kemp, p. 328 o saturated hues around equator, B & W at poles, gray axis o saturation ("chroma") introduced as a distinct variable o retained Newton's placement of opposite complementaries o retained Lambert's decreased discrimination toward white, added decreased discrimination toward black 1840 Johann Wolfgang von Goethe A Romantic's return to mysticism -> Color wheel, Kemp, p. 297 o reduces number of colors, improves complementarity o anti-Newtonian, nonsensical scientific explanation of color o more color associations, including: o yellow/blue = o force/weakness o action/negogiation o acid/alkalis -------------------------------------------------------------------------------