T3D Re: Pulfrich Effect Timing Measurement

[Dave Combs <dcombs@xxxxxxxxxxxxxxxx>]

I have been unable to locate anyone who has documented the "darkened eye 
delay time" involved in Pulfrich Video. In an experiment which I 
conducted I was able to conclude that the delay time is probably 
significantly less than 1/30 sec. Here is the general design of my 
experiment:

My source of constant rotation speed was my now nearly useless Dual 
turntable which has speeds of 33 1/3, 45, and 78 rpm. I drew an 8 inch 
circle on a piece of paper. I drew a dark radius line at 12 o'clock. I 
drew several tic marks on either side of the radius on the circle at 
points which precisely indicate the amount of rotation in 1/30 sec 
increments. I placed the paper on the turntable and turned it on at the 
desired speed. I then video taped the rotating paper with my camera set 
at a shutter speed of 1/1000 in order to freeze focus each frame. Upon 
viewing the resulting video while wearing a pair of Pulfrich glasses, my 
hypothesis was that I would see two rotating radius lines with the line 
seen by the darkened eye lagging behind the line seen by the clear eye. 
To my surprise I could detect no lag or delay. Both eyes were able to 
follow the line around the circumference with no problem and seemingly in 
sync. If the delay were close to 1/30 sec or perhaps more the radius line 
for the darkened eye should appear one or more tic marks behind the line 
for the clear eye. Since this did not happen my conclusion is that the 
delay time is probably significantly less than 1/30 sec--how much I don't 
know and haven't figured out a way to measure it.

If anyone can point out any fallacies in my experiment or suggest other 
ways to measure this delay I would appreciate it.


Dave Combs
dave@xxxxxxxxxxxxxx


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End of TECH-3D Digest 346
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