Ursa Mini Pro 4.6K - lens covarage questions (Thank you)

Hi, I appreciate a lot those being kind and answering questions to newcomers like me. I would mostly use the camera for independent films, some documentary work but only 10-20% "run and gun" shooting.
Here are some things I would love some suggestions:
1. In general, if I get any Canon photo lenses (prime or zoom) for the UrsaMini 4.6 Pro should they be Full frame or APS-C ?
2. At the moment I have Tokina 11-20mmm and a set of Rokinon Cine DS (24-35-50-85) . I would like to get few zoom lenses to add to the Tokina lens. Choices (based on around $6-7000 budget):
a) The new Canon Cine Zoom 18-80mm ($5200) plus another Canon/Sigma/ ? (FF or APS-C ?) zoom up to around 200mm
b) The 2 Sigma cine lenses (18-35mm & 50-100mm - $3900 each)
c) Regular (photo) Canon L series zoom (FF or APS-C ? )
d) Other choice?

Thanks a lot .
Alex - Portland Oregon area

The 4.6K sensor has a diagonal of 29.08mm. The image circle of the lens should likely be about 30mm or more. Many APS-C lenses designed for smaller sensors actually have image sensors that will cover the 4.6K sensor. For example the Rokinon 16mm APS-C lens has an image circle of 30mm and will cover, but their 10mm lens will not. Be very careful though as the 4.6K sensor is actually a little larger than Super 35 so some cinema lenses will in fact vignette if their image circle is designed to be very close to the official Super 35 film dimension.

The Sigma Cine Zooms you are considering have image circles that are published on the lens barrel: 28.4mm. That is too small to shoot using the full sensor but any window would be fine. Sigma even cautions that they will vignette on the 4.6K sensors but some users such as Note have said they work well for him with any vignette appearing as very slight fall off in the corners.

The Rokinon lenses you mentioned all cover the 4.6K sensor.


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Hey Rick while you are here I'm using my B4 mount on my Mini as I save up for some PL glass. I just wondered if S16 glass fits the windowed sensor HD 1920X1080 size without vignetting.
That way I could leave the PL mount on the camera for a wider range of work.

I love my Tokina 50-135 T3 Cine zoom:
https://www.amazon.com/Tokina-Cinema-50 ... 012MDJUAS/
The advantage over the Sigma 50-100 is more zoom range and it keeps focus when zooming while the Sigma 50-100 Cine doesn't (at least that is what I have heard from reviews).

ATM the price is nice at Amazon, but it keeps wildly fluctuating.

The Sigma 18-35 cine is very nice and has no problem keeping the focus. I have no problem with vignetting.

Hey Rick while you are here I'm using my B4 mount on my Mini as I save up for some PL glass. I just wondered if S16 glass fits the windowed sensor HD 1920X1080 size without vignetting.
That way I could leave the PL mount on the camera for a wider range of work.

Hey Stephen, yes. In fact, I have a couple of super16 lenses that will cover the 2k window.

The one I use most is the Canon 8-64mm T2.4 - beautiful lens. That way I can leave the PL mount on and for a lot of work - documentary, corporate events etc - and the Canon zoom has a great range and is quite fast. Then if I need to use my Super 35 PL glass, no mount change.

Thanks so much, that is exactly what I wanted to know

Tristan is correct but just rely on the image circle of those lenses to be your guide. Please shoot 2K 16:9 even if you're delivering HD as the extra room can be useful for reframing in post or stabilization. If the shoot is well-controlled and you are confident you won't need to stabilize or reframe, then you can always downscale the 2K in post if you like to get that slightly larger angle of view.

The image circle should be a little larger than the 4.6K sensor diagonal of the 2K 16:9 window: about 12.93mm. If you still want to shoot in the HD window, the diagonal is 12.12mm. Super 16 is larger than 2K on the 4.6K sensor with a diagonal of 14.55mm.

The problem with 16mm lenses is the diagonal is only 12.66mm--perhaps fine for HD on the 4.6K sensor, but may vignette on the 2K 16:9 sensor.



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I agree changing the PL mount for the B4 mount is an inconvenience and not something you ever want to do in the field. But the advantage is the high quality of lenses that you may have to choose from and the greater zoom range while maintaining parfocal performance at sometimes brighter apertures. The 8x Zoom of the Canon 8-64mm PL lens has a very useful wide angle, but the telephoto may be shorter than you want. If you go with B4 lenses, your zoom range can increase. For example, the Fujinon 20x7.8B M10 Cine Zoom zooms out to 156mm. I don't like going that far but I do use around 110-120mm often where the lens stays at T2.4 like the Canon. If I go to 156mm, there is some fall off in light so I avoid it while zooming where feasible.

The Fujinon 20x7.8 is my go-to event lens with the SLR Magic APO T2.1 PL primes are my choice in more controlled shoots.


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How do you find swapping the mounts Rick? I did it when I first got the camera and was worried that constant swapping would wear on the screws etc... and shorten the life of the camera.

Stephen, I share the concern, and tend to minimize the number of times I change the mount. I leave the BMB4 mount on the camera most of the time now as my Fujinon is primarily used for events one or two times a week perhaps for about nine months. When I shoot for my own projects, I use the APO (typically through the summer). I've done many events with the APO and concluded this year that I think my results are better with the flexibility of the zoom for events.

If I was changing the mount every week, I'd be better off staying with Tristan's option of a fast Super 16 parfocal zoom like his Canon 8-64mm PL zoom. My APO primes definitely give me the best image and I expect will be used more when I have additional focal lengths and can change a PL lens quickly.

Changing the primes is a minor chore as I use the Misfit Atom and Chrosziel Fluid Zoom with all my lenses. It's not simply pop off and pop on when I work alone. I need to be able to change a prime in less than 10-15 seconds! Is that possible working alone?

To extend the life of the mount and the screws, be careful not to over tighten the screws. Always use the torque wrench with the recommended setting of 0.45 Nm. I'm still using my original shims even though I have two additional sets of shims just in case one is damaged or show signs of wear. So far, so good.


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