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August 21, 2008

Mach Banding for Mystics

I first became aware of auras as an undergraduate in Nebraska investigating mysticism. Mysticism as in the American Spiritualist Church, descended from the spiritualist movement that peaked in the U.S. and the world around 1890-1900. Harry Houdini spent a lot of his time debunking spiritualism. Unsuccessfully it would seem, since it was still around in 1968, in Lincoln, Nebraska yet, when I ran into it and discovered that my aura is blue.

Lincoln is a holy city of sorts, and has a lot of spirituality going on all the time; revival tents are a permanent feature on the outskirts of town and I spent as much time exploring this side of Lincoln as I did the Haymarket bars. The thing is, you have to go with your sense of the crowd when broad spectrum traveling, so when a formidable Nebraska matron wearing a hat and granny shoes tells you that your aura is blue, you believe it, at least for a while. Well not very long, actually. Maybe not at all; perhaps I was just being polite. She was nowhere near as scary as the snake handlers.

Mach bands came ten years later. As a budding artist, I was investigating human perception and came across a reprint from Scientific American that discussed the Mach band phenomenon in some detail. Mach bands are areas of visual uncertainty that occur on either side of a boundary in the visual field. Contrast and complimentary colors enhance the effect. The cause seems to be the confused response of the receptor cells (the rods and cones of the retina) that lie on either side of the boundary; they respond sometimes as if they were on one side, sometimes as if they were on the other side. This results in bands that are slightly lighter or darker on each side of the boundary. Usually we ignore these perceptual flaws; observant people, like artists, have noticed and painted Mach bands for years.

Auras came up again for me as a practicing artist in the guise of halos, nimbuses and mandorlas. All the ways artists have used to indicate spiritual power residing in the person of a human being. Is art imitating life here; did some artists actually see, or imagine they saw, an aura around some saintly human being and painted what they saw? Or did the artistic convention of the halo manufacture the mindset that allows for the idea of an aura to exist. For the painter the choices run from the delicately incised circlets of Caravaggio to whole body light shows that are common to transfiguration paintings. To date, for my saints I choose nothing, preferring to bathe the holy personage in light as a mark of their spiritual power.

The final piece of the puzzle came from my student Michael Jarvis, who is both a scientist and an artist who likes to paint Mach bands. He told me that recent research had found that our eyes make constant micro movements. For me, this explains the Mach band phenomenon; the apparent confusion of the receptor cells on either side of a boundary is actually their faithful response to stimulation as we constantly slightly jiggle the camera. Perhaps auras are explained as well. Perhaps the emotional impact of being in the presence of a spiritually powerful individual is so exciting that the micro movements of the eye increase in frequency or amplitude or both to the point where the Mach bands become noticeable to the average human observer. I have only one more point to add, which is that mine is blue.