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Film back size

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Dan Wiese
Film back size
on Mar 8, 2008 at 5:53:27 am

I'm trying to do some motion tracking for a music video with boujou4 and I can't get the film back size (size of the cdd in mm) right for HVX-200 that my footage was shot with. I've looked all over and Barry Green posted somewhere that it was roughly 5.24 mm by 2.95. Has anyone had any expierence with this or does anyone have a real answer from panasonic?

Thanks,

Dan Wiese


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Kirk Melby
Re: Film back size
on Mar 10, 2008 at 10:01:30 pm

No real answer form Panasonic, but I checked with our CG guy and he's been using 4.6809 X 2.6330

I know he worded backwards from some real world measurements, but I'm not quite sure how he calculated it.

Hope it helps.



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Lars Wikstrom
Re: Film back size
on Mar 11, 2008 at 7:17:47 am

I use Syntheyes for my 3D tracking and when it asks for the film back size it is just the size of the image like 960 x 720 or if I stretch it out first to 1280 x 720 for instance.

I am surprised your software is not that simple.

-Lars



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Jeff Brown
Re: Film back size
on Mar 11, 2008 at 3:02:41 pm

I also use Syntheyes, and it does have a setting for image aperture (it's called "Back Plate"). You get more accurate lens calculations if your image aperture is also accurate.

-jeff


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Lars Wikstrom
Re: Film back size
on Mar 11, 2008 at 9:25:58 pm

Sorry, I miss understood the question.


The process that I use with SynthEyes is to first get my HVX200 footage in to Shake and resize it to 1280 x 720 (which is what I shoot at). Then I apply the lens node to undistorted the image. I shot my garage door that had a bunch of lines on it so I know how much to undistorted the image to make it flat.

Render that out as a self-contained QT movie for SynthEyes. The back plate comes in as a default 24.892mm x 14.002mm.

Since 3d programs, that I know of, don't render with lens distortion I undistorted it first and then add it back in when I do my final composite.

-Lars



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