>On Tue, 19 Mar 1996, Meryem Constance Ersoz wrote: >The phenomenon has nothing to do with film. It's the phi-thing playing a >trick on you. You may remember the early days of hifi, when with had >these turntables we used to place vinyl-records on? Well, the fancy ones >had a little knob with witch you could adjust the speed of the turntable. >So how do you know the speed is exactly 33 rpm? Was it a cute little LED- >display? Or maybe you had to actually count? Nope. The solution was a >stroboscope. Along the edge of the turntable there was a series of small, >rectangular dots. There was a small light right by the plate, so you >could see them in the dark. The cute thing was, if you played the record >at *exactly* 33 rpm, the dots would seem to stand still! If you played it >to fast they would move clockwise, if you played it to slow they would >move counter-clockwise. Welllll, really they weren't LED's but neon or some other gas , lighting surfaces spaced differently. The gas turns on and off quickly, not slowly dimming like a lot of bulbs. It's the same thing with the wheels, it all >depends on the speed of the wheel, and the distance between the dots, >sticks or whatever that makes you see movement. >Following this, one could imagen a complete picture made in such a way >that you could only see it while rotated at a certain speed. > How about the flying spot scanner? superior color TV, long before today's Color TV >A couple of years back, when I had a year of psychology, our teacher >demonstrated the phi phenomenon. He had this device with two electric >lights on, lit one at a time. He could adjust the speed of the on-off >turning, as well as the distance between the lights. When everything else >in the room was completely dark, and the two variables described was >correct, it would seem as if the *same light went back and forth*, between >right and left. > >The phi phenomenon is one of the triumphs of gestalt psychology, a branch >of psy. reaching it's peak in the 30's and 40's. They where particulary >interested in the phi phenomenon and other odditys that played tricks on >our eyes. For further reading: try the book "Psychology" by Gleitman. > >Hope this cleared up something (and, although probably being one myself >once, I hate these little smart asses as well). Sincerely, Art Prutzman NE Pa. ---- To signoff SCREEN-L, e-mail [log in to unmask] and put SIGNOFF SCREEN-L in the message. Problems? Contact [log in to unmask]