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stereography / Focus pullers?


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#1 Jad Beyrouthy

Jad Beyrouthy
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Posted 27 September 2012 - 04:26 AM

I want to test a couple of 3D shots soon (as a DOP) with apost production house that is planning to establish its 3D workflow.

I researched a lot about 3D cinematography but i was wondering about focus pulling with two cameras.


Is there anything i have to know about focus pulling two cameras (arri alexa) in a 3D rig (beam splitter)

Any special features? tips? tricks?

I still didn't see the rig and never used one so i need some help from u guys.

Thank you,
JB
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#2 John Waterman

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Posted 27 September 2012 - 08:41 AM

Hello there. I am a local 600 focus puller and a 3D rig tech, and I would be happy to answer your questions. There are a number of things to consider with focus and 3D. There are two cameras and two lens in a 3D beamsplitter rig. Each lens must be matched to the other in all aspects (focus, iris, and focal length). If you wish to pull focus during a shot, a common thing to do, then both lens have to pull together, and in perfect sync. The standard way to do this is to use motors to drive both lens, controlled with a lens control system. Cmotion has become the defacto standard LCS to use. The Cmotion Cvolution can control up to 8 motors, allowing for sync focus, iris, zoom, and rig IA and C controls. Most lens have some variation in the focus scale from unit to unit, so it is not enough to have the motors simply running at the same time. The Cmotion Cvolution can sync up to 32 points on the each scale. During my camera prep I calibrate the focus scales using the Cmotion so that each mark on the lens matches the other lens. (10' matches 10', 15' matches 15', 30' matches 30', etc). I do this for every lens pair and save the calibration to a usb thumb drive. The Cmotion has a wireless hand control that when properly set up will control both lens for focus, iris, and zoom. I own a 3D Cmotion Cvolution kit and would be happy to answer any more questions.
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#3 Jad Beyrouthy

Jad Beyrouthy
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Posted 28 September 2012 - 05:08 AM

Hey John,

Thank you for the deatails, really helpful.
I will research all the info.

Thank you again,

JB
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