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Sensor to Flange distance of URSA Mini PL


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#1 Tom Visser

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Posted 08 February 2018 - 03:41 AM

Can anyone tell me what the flange distance is for the URSA Mini PL (not the Mini PRO - unless they happen to have the same distance - highly probably I guess)?  Specifically, the distance from the sensor to the face when you remove the PL mount.  Why?  I'm trying to fabricate a custom adapter that happens to use the B4 adapter, but I suspect that with the optics in there, its not simply the standard 48mm of the typical B4 flange distance.

 

blackmagic_design_cinecamursamtb4_b4_lens_mount_for_1496078415000_1186264.jpg


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#2 Phil Rhodes

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Posted 08 February 2018 - 05:08 AM

For that you'd need to get hold of a camera and measure it. There isn't, as far as I know, any standard involved in a bit of custom design like that.


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#3 Dom Jaeger

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Posted 08 February 2018 - 05:54 AM

You'd want to measure the PL mount from flange to seat and subtract that figure from 52.00mm to get the optical depth from seat to sensor. It's very hard to measure to the actual sensor since it will have a protective cover glass. (But no OLPF with Ursa Mini I think?)

Given that flange depth tolerances are around 0.01mm, the final shimming is best done with a test lens that is accurately collimated.
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#4 Tom Visser

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Posted 08 February 2018 - 06:14 AM

You'd want to measure the PL mount from flange to seat and subtract that figure from 52.00mm to get the optical depth from seat to sensor. It's very hard to measure to the actual sensor since it will have a protective cover glass. (But no OLPF with Ursa Mini I think?)

Given that flange depth tolerances are around 0.01mm, the final shimming is best done with a test lens that is accurately collimated.

 

That's more or less the plan, get close as possible (hopefully undercutting a bit) with the first machined part - assemble the front and rear mounts, then shim until it tests spot on with the lens, then machine the final part maybe 0.5mm undercut so I can have 1 shim in place in case I need room to adjust either way in the future.


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