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Topic: Low Light For Cinema 3D
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Martin Jones
Phenomenal Film Handler
Posts: 1269
From: Thetford , Norfolk,England
Registered: May 2008
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posted August 25, 2013 05:22 AM
Vidar,
Strictly speaking, 3D should NORMALLY only show action taking place further away than a "window" which is effectively the plane of the screen. Anything that approaches the viewer closer than that should be restricted to something (such as an arm) that is wholly within the field of view and NOT cut off in any way by the screen edges. As long as those rules are followed great 3D can be achieved.
BUT, there is another rule that can ONLY be followed (for movies) if the presentation is on a large screen...
The "Left" and "Right" images of an object at "infinity" MUST, by definition, be placed 65mm (approx) on the viewing screen surface to appear to be at infinity to the viewer. Anything closer than this will have the images closer together, varying as to how close the depicted object is. So, each auditorium will require a slightly different set-up depending on screen size, throw and how the images are projected.
In fact, back in the 50s these factors were taken into account when setting up camera separation and convergence while actually filming, a typical optimum screen size and theatre layout being assumed: there were special calculators manufactured for the purpose.The distance at which convergence was set defines the "window" (plane of the viewing screen).
3D in TV can never therefore give a true representation... a "foreshortened" version of the spacial content of the original is the result. I understand that the cameras used by SKY for football presentations actually have their lens separations wider than human eyes to enhance the appearance of depth: an example of taking a "typical" screen into account when actually filming.
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Retired TV Service Engineer
Ongoing interest in Telecine....
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Hugh Thompson Scott
Film God
Posts: 3063
From: Gt. Clifton,Cumbria,England
Registered: Jan 2012
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posted August 25, 2013 06:39 AM
Like all gimmicks, the public soon tire of them and look for the
next "innovation". We are speaking in the main, of people who
spend half their lives on mobile phones, and watch films on them.
Give the public what the want, and they no longer want it.As for
low light projection, didn't they change the opt lighting to laser
for their 35mm sound some years back, that caused a bit
of consternation with the projectionists. Perhaps Graham could
shed more light, pardon the pun.
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