So, we ask, how do you know how long these poles should be as they recede? I was taught, he says. Not by any formal teacher, but by casual comments by friends and acquaintances. How do you know about shadows? He learned that too. He confides that for a long time he figured that if an object was red, its shadow would be red too. “But I was told it wasn't,” he says. But how do you know about red? He knows that there's an important visual quality to seen objects called “colour” and that it varies from object to object. He's memorised what has what colour and even which ones clash.
Via Jason Kottke [1], “Senses special: The art of seeing without sight [2]”
An artist who can draw complicated scenes upon request, despite the rather small handicap of being blind—a very interesting article indeed.
[1] http://www.kottke.org/remainder/05/02/7463.html