> Whatever it is, that is what you see. If it moves faster than 50 Hz you 
> either see it not moving at all or, viewed in the right direction, as a 
> semitransparent surface. If you can prove that you can see something 
> moving at, say 200 Hz, I have a couple of friends working on the retina 
> that would be most interested in such a physiological anomality. ;)

It's easy to see things moving above 200 Hz.

One method is to light the thing with a special light source (eg a pulse at 
190 Hz or something).  On high speed machinery they use this technique so 
that operators don't accidentally put their fingers into something moving at 
200 Hz....

Second is to quickly move your eye from side to side to try and "follow" the 
movement.  You eye can move at an incredible angular speed to follow 
objects, and in doing so will make the object you are tracking look less 
blurred while the surroundings get blurred.  Try flicking your eyes from 
left to right as you watch a wheel that is spinning too fast to see, as you 
do it some parts become clear.  If you do this while looking at the beam of 
a cheap projector (one that uses a rotating colour wheel) you will see the 
RGB primaries separated because they are hitting different parts of your 
retina (I assume this changes at 60 * 3 = 180 Hz).

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