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>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.
 
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