When you walk from a bright sunny street to a dimly lit pub, the pub initially feels entirely dark inside. After a while, however, your eyes habituate to the low light level, and you see it as highly varied in light level: it looks dark inside that mouse-hole in the wall, bright where the uncovered light bulb is, and, scattered around the room, you see dozens of other light-levels spanning the dark-light range. This is clearly advantageous for you, because you effectively began as blind in the pub, and minutes later could see. In order to make it happen, though, you underwent a kind of “world shrinkage,” in particular a kind of “luminance shrinkage,” where luminance refers to the amount of light coming toward your eye from different directions around you. When you first entered the pub, all the differing luminance levels in the pub were treated by your visual system as pretty much the same, namely “very very dark”; at that point in time your eyes were habituated to the wide world of luminances found on a sunny day outside.
Posted on: Thu, 06 Mar 2014 15:38:18 +0000
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