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film gate in camera tracker options

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jamie_fenn

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film gate in camera tracker options

PostWed Aug 07, 2019 10:51 pm

What if your camera doesn't show up in the film gate selection of the camera tracker options?

Im using Gh5 and a BMPCC.

Is there a default selection I could/should use?
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Bryan Ray

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Re: film gate in camera tracker options

PostThu Aug 08, 2019 2:54 pm

The Film Gate measurements are in inches. Consult the VFX Camera Database for the sensor dimensions for your camera:

https://vfxcamdb.com/
Bryan Ray
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http://www.musevfx.com
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jamie_fenn

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Re: film gate in camera tracker options

PostThu Aug 08, 2019 3:24 pm

So it doesn’t matter which camera I select as long as input the correct inches?
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Bryan Ray

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Re: film gate in camera tracker options

PostThu Aug 08, 2019 4:56 pm

Yep. The purpose of setting the film back is so you can derive, in tandem with the Focal Length, the correct Angle of View. AoV is the only thing that actually matters during the track. (Caveat: Depth of Field calculations depend on the gate size, too, but most people don't try to get that programmatically.)
Bryan Ray
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jamie_fenn

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Re: film gate in camera tracker options

PostThu Aug 08, 2019 11:57 pm

Does it take into account if I use the stabilization in DR? The Crop? Or should I not use the stabilization?
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Bryan Ray

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Re: film gate in camera tracker options

PostFri Aug 09, 2019 2:38 pm

Stabilization and a crop will definitely play havoc with the solution. I recommend tracking the original image, then perform your stabilize on the composite rather than the source.

You could, technically, do the math to determine how the crop affects the AoV, but you'd still have other artifacts from the stabilize, like data loss from filtering. It may not seem like much, and it may be totally invisible to the eye, but ideally you want a solve that's accurate to within less than a pixel. Also, in the final composite you could have issues with motion blur not matching direction.
Bryan Ray
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jamie_fenn

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Re: film gate in camera tracker options

PostFri Aug 09, 2019 4:44 pm

Oh duh, that makes sense. Thanks XD

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