Re: Double depth

[T3D Bob Aldridge <bob.aldridge@xxxxxx>]

John Bercovitz wrote re: Double depth

->There are various rules for the maximum allowable depth in a 
->scene.  Seems like the best ones have to do with the maximum 
->amount of parallax on the film and that that amount is usually 
->about 1/30 of the focal length of the system.  
-> 
->For miniature format with the usual 35 mm lenses, this works 
->out to about 1.2 mm of parallax.  If a scene has a lot of depth 
->in it, some people will crop the mask a similar amount for 
->"double depth".  Does this cause viewing problems?  I think I 
->can see where it would be a problem for projection because the 
->window would be really close, but what about in a hand viewer?
-> 
->The reason I ask is that I just calculated the way I set the 
->window in my medium format viewer and it's at about 4' (1.2 m) 
->which is approximately double depth.  I have no problem with it.  
->I haven't heard of anyone having a problem with it.
-> 
->So if double depth isn't a problem, where does this limit to 
->the amount of a depth in a scene come from?

Surely it came from PROJECTION.

If you decide to put the window at the same distance as the screen (i.e.
the frames are co-incident) then extra depth in the scene will give rise
to excessive separation of the infinity points...

Of course, if the closer items in the scene are poking through the
window, there's no problem. There's also no problem with extra depth
behind the window (i.e. the window is set closer than the usual 7 feet),
if the window is brought in front of the screen.

Bob Aldridge      Stereoscopic Society Projectionist


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End of TECH3D Digest 33
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