Prof. Jeremy Wolfe graduated from Princeton and obtained his PhD from the Massachusetts Institute of Technology. He worked on binocular vision and visual adaptation before taking up his current interest in visual attention. Today he is Professor of Ophthalmology at Harvard Medical School and the director of the Visual Attention Lab of Brigham and Women’s Hospital in Boston, USA.

 

Rudolf Arnheim, who died this year at the age of 102, quite literally wrote the book on ”Art and Visual Perception”. His chapter on Light comes surprisingly late; sixth out of ten chapters. Arnheim comments that, ”If we had wished to begin with the first causes of visual perception, a discussion of light should have preceded all others, for without light the eyes can observe no shape, no color, no space or movement.”

 

However, he goes on, ”since man’s attention is directed mostly toward objects

and their actions, the debt owed to light is not widely acknowledged.” Light has these two faces for us. The Bible proclaims pure light as the first creation, well before the sun and stars. They appear only on Day Three. Jewish tradition imagines that this primal light made it possible to see from one end of the earth to the other but that this light was so overwhelming that 6/7ths of it had to be withdrawn. Because Psalm 97 declares that ”Light is sown for the righteous”, the tradition imagines that the light that was taken back is preserved as a reward, to be revealed to the deserving at the end of days.


In the meantime, we are less attuned to light, itself than to differences between the light reflected from one surface and another. As Helmholtz phrased it, we ”discard the illuminant”. We throw away information about light itself in order to recover information about objects in the world. Hansel (of Hansel and Gretel fame) can collect ”white pebbles” during the day with the assurance that they will shine ”like newly coined silver pieces” in the moonlit night even though a white pebble at night reflects much less light than a lump of coal in the day. We barely notice the yellowness of light from an incandescent bulb. Our visual system is more concerned with assuring that the banana that is yellow in the kitchen, looks yellow on the playground.


Still, we have not completely lost contact with that primal light. It modulates our mood and adjusts our internal clocks. Light, as light, functions largely outside of our routine awareness while we are preoccupied with what it illuminates.