Ursa Mini Pro G2 w/ B4 Mount Question

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Ursa Mini Pro G2 w/ B4 Mount Question

PostFri Jan 07, 2022 3:56 pm

This is my first post on the blackmagic forums so thanks in advance for the help!

I have a set of UMP G2's with the B4 mount attached and a Fuji XA20sx8.5BERM-K3 ENG Lens attached to that mount. I've added the additional .10 shim along with the .50 shim that comes when you remove the EF mount (for a total of .60) but I cannot seem to get the lenses to be parfocal and they also have some chromatic aberration issues right before / after hitting focus.

What could I be doing wrong?


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Re: Ursa Mini Pro G2 w/ B4 Mount Question

PostMon Jan 17, 2022 10:42 am

You need to set your backfocus every time you change a B4 lens!

By the way you need three shims: standard is a black 0,10 and a metal 0,50. When using a B4 mount you have to add an extra 0,10.

Chromatic abberation is always visible with this kind of (cheap) lenses. I use expensive Canon HJ lenses but if you know how to look you always see a little chromatic abberation and blue fringe. For really clean images you need lenses which can’t zoom, or zoom a little. My Sigma ART 18-35 (€999,00) gives a very clean image compared to my Canon HJ11(€ 34.000,00 list-price).
Don’t expect miracles with a lens of ‘only’ $ 5995,00 and a zoom factor of 20.

To use remote iris you have to set auto iris to ‘off’ in the camera menu and set auto iris to ‘on’ on the lens itself.

If you have other questions please don’t hesitate to ask; I’m working a few years with Ursa’s and BMPCC’s on Atem switchers.
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Re: Ursa Mini Pro G2 w/ B4 Mount Question

PostMon Jan 17, 2022 2:29 pm

That’s correct. I use a .50+.20 shim with my URSA Mini 4.6K with Fujinon 20x7.8 BRM B4 Cine Zoom. It’s parfocal and performs miracles. The Cine Zoom does not include a 2x Extender and the emphasis seems to be on a quality Super 16 image.
Rick Lang

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