Friday, December 10, 2010

color in black and white

The experience of color television doesn't require a special TV. This is because of the Benham effect, which occurs when the experience of color is produced by rapidly oscillating patterns of white and black. Differences in the phase of this oscillation produce different color experiences.

You can experience the Benham effect for yourself here.

Although we don't know exactly what causes the Benham effect, we do know what relationship between phase and oscillation speed produces which color experience. In 1968, James Butterfield employed this knowledge to broadcast color information from a black and white TV camera to black and white TV sets. The idea is to use a rotating disk, half of which is black, the other half comprising a sequence of filters (in primary colors, red, green, and blue). The filters are placed to ensure that only the relevant color signal (whatever makes it through the filter) is phased appropriately with respect to the rotating disk. The end result is a flickering image which reproduces the sensation of color in the viewer, even though it is projected on a regular black and white television.

Read more about the Butterfield Color Encoder here.

According to Arthur Winfree:
Its first public demonstration was a soft-drink advertisement over station KNXT in Los Angeles. Nothing was said about color, to the consternation of thousands of viewers who seemed suddenly to be hallucinating. Its last public demonstration was in Argentina during political advertisements by Eva Peron.

~ Winfree (1980 / 2001) The Geometry of Biological Time, 2nd ed.

1 comment:

Pila Grande said...

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