In 1964 an exhibition of thirty-one artists associated with this development was organised by the critic Clement Greenberg at the Los Angeles County Museum of Art. It differed from abstract expressionism in that these artists eliminated both the emotional, mythic or religious content of the earlier movement, and the highly personal and painterly or gestural application associated with it. ‘The colour field painters’ was the title of the chapter dealing with these artists in the American scholar Irvine Sandler’s ground-breaking history, Abstract Expressionism, published in 1970.įrom around 1960 a more purely abstract form of colour field painting emerged in the work of Helen Frankenthaler, Morris Louis, Kenneth Noland, Alma Thomas, Sam Gilliam and others. You can learn more about vision at the UCSD Color and Vision Database.The term was originally applied to the work from about 1950 of three American abstract expressionist painters Mark Rothko, Barnett Newman and Clyfford Still. The next section is about infrared spectroscopy and degrees of freedom. Note that if your eyes were sensitive to much longer wavelengths you would look through a sort of "infrared fog", since you would see heat energy everywhere. Retinal sensitivity sometimes extends (with very low sensitivity) to 1000 to 1050 nm. Wavelengths shorter than 315 nm are absorbed by the cornea (causing injury) and do not reach the retina. "Scotopic" (dark-adapted) and "photopic" (light-adapted) sensitivities differ scotopic peak sensitivity (of the rod cells) is at about 500 nm, while photopic sensitivity (of the cone cells) peaks at around 550 nm. Since most of us have similar sensitivities we can agree on primary colors, so the garment industry has nothing to fear. Now you can understand why people can have violent disagreements over what color something is: no two people see exactly the same thing, yet we assume that color is something objective.
Ucsd cplot 2 full#
This leads to a vaguely disturbing contrast between sensation and perception: your eye sends only three kinds of signals to your brain, yet your brain "constructs" the full color spectrum of "reality" from them. The number of signals for any one of these ranges depends on both the intensity of the light and the sensitivity at that wavelength. Similarly, 475 nm photons will cause about equal numbers of blue and green signals, with only a few red this will be interpreted as a sort of bluish-green. If 650 nm photons hit your retinae, your brain will receive a mixture of green and red signals, with more red than green but not too many of either. Recall that the "intensity" of a sensation is proportional to the frequency of nerve impulses. The cone cells of the human eye are sensitive to 3 wavelength ranges which the eye interprets as blue (narrow, with a peak near 419 nm), green (broader, with a peak near 531 nm) and red (also broad, with a peak near 558 nm, which is actually more like yellow!):Īll of the colors which your mind perceives are constructed from combinations of relative intensities of these three "wavelengths": red, green and blue are the only "signals" your brain receives from your eyes. Rhodopsin is the protein in human rod cells as well as in many photoactive organisms. Retinal linked to rhodopsin has a peak sensitivity of about 496 nm. (Note that at the level of proteins, geometry defines function this business of shape-changing, as well as "key and lock" shape fitting, is a ubiquitous signaling mechanism in the world of molecular biology.) The specific protein to which the retinal is linked determines the range of wavelengths to which it is sensitive. It has the effect of activating an enzyme (phosphodiesterase) which in turn hydrolyzes hundreds of "cylic-GMP" molecules (guanosine 3' - 5' phosphate) which in turn effects the sodium channels in optic nerves, initiating a nerve impulse. This change in geometry takes place in about 6 ps.
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