Another Ursa Broadcast Lens Question

I didn't want to hijack the other thread, but I also have questions about b4 lenses on the Ursa Broadcast.

I am very familiar with all terms in regards to ef and micro 4/3's lenses but I have a lot less knowledge about b4 lenses. I'm looking to invest in a video system for a church and want to make sure I know what I'm talking about when it comes to these lenses.

Using its native b4 mount does the Ursa Broadcast have a crop factor or change to the field of view?

Would anyone be kind enough to explain to me what all the numbers and letters stand for on the descriptions of B4 lenses?

Here's an example lens, Canon J21aX7.8B4 WRS SX12 IfXs lens W/2X Extender and 4:3/16:9 Crossover. I understand everything that's underlined.

Those are the relevant questions; if you want some more context we are a church of about 1,000. The cameras will be at their closest 50' from the speaker and the farthest 75'. For teaching I only need a waist upshot, I do not need a wide lens at all, and then for music, it would be great to be able to zoom into guitar players hands and see faces close up. I've done test shots with my BMPCC4K and around 200mm (after crop) is pretty sufficient for teaching. I would need much more though to get close-ups of hands and faces. If I understood the numbers better on B4 lenses I could get a rough estimate and plug some of that data into a camera app I have. I have a suspicion that everything is too relative to get hard numbers out of but I'm sure there are ways that I can get rough estimates.

Thanks for the help!

With a PL mount the UB should be considered a s16 sensor, 13mmx7.5mm.

With the B4 mount which includes the integrated 1.5x extender the UB should be considered 2/3" , 9mmx5mm-ish.

Good Luck

Edit: 2/3" is half micro 4/3" you can use any m43 calculator and half it to get your 2/3" equivalencies. The zoom lens is a zoom ratio 21X times the widest focal length 7.8mm. Your lens is a 7.8-163mm zoom with the 2X doubler 15.6-366mm. This will cost 2X stops of light so likely those CUs are going to be really dark.

With the B4 mount which includes the integrated 1.5x extender

So I think that answers my 1st question then, there is a built-in "crop factor." So if I get any measurements from a B4 lens then i should multiply that by 1.5

You could do it that way, the 1.5X is a guess, It has to be enough to cover 2/3". I was editing my post, when you replied, but I think it's easier to simply half m43.

pCam is an absolutely stellar app for just about any camera calculation you can imagine.

Good Luck

yeah that's the app I have! thanks for the info

Jumping into this thread.

I'm still kind of wondering..

1) The B4 lenses tell the focal length in the same manner as all other lenses, right? Where everything is measured in 35mm sensor standard, and needs to be cropped to whatever mount and sensor you are using? My Sony A6500 has a crop factor of 1,6, so a 50 mm lens equals 80mm, a 30 mm lens equals 48mm and so on.

2)
The crop factor on the Ursa Broadcast. I've read stuff here on the forum about a 1,5 extender. But when that is taken into consideration, the Ursa Broadcast should be considered a 2/3" camera, right? Which means the crop factor of the lenses are 3,93, so that a B4 lens set on 100mm zoom equals 393mm?

I'm coming from the still camera world, and have been shooting film with such cameras, so I kind of need to know when looking into new gear, so I don't go and buy the wrong lenses! =P

Christoffer, according to the ACS Lens Chart, a Ursa Broadcast 2/3rds Camera (9.6x5.4mm) with a 80mm lens would have the same horizontal angle of view as a 300mm lens on a full frame 35mm stills camera (36x20mm), or 175mm on a Standard 3-perf 35mm Cinema Camera (21x12mm).
Cheers

Thanks, Danny, for bringing in some clarity for me!

This is just an approximation from the ASC chart, in practice, every Camera has its own size sensors, and actual angle of view can vary a little, as Howard pointed out in his post. The Ursa Broadcast sensor is actually closer to a 1-inch size sensor (Actual sensor size 13.056mm x 7.344mm), so with the 2/3rds Mount correction the AOV May be slightly wider, but this is a close comparison. That said, most 2/3rds lenses used are Broadcast type zooms, so you can adjust the zoom to get the desired AOV.
Cheers

I'm trying to figure some things out for my work and ran across this thread. Have an issue trying to get solid info on lens comparisons.

I have a test set up with 2 B4 lenses on URSA Broadcast cameras.
And then I have a BMPCC 6k Pro with a canon 70-300mm zoom lens.

It looks like the B4 lenses sit around 100mm to match the 300mm of the full frame shot.
Some of my research seems to suggest there is a 4x factor, but this looks much closer to a 3x factor.

What we want to do is get a new URSA Broadcast G2 with EF mount and a canon servo lens with EF mount that can get us at least what we can get with our Fujinon B4 lens (8-170mm).
But That would mean I'd need the $70k Cine-Servo 50-1000 mm lens which seems a bit excessive.

I wish there were better options out there for large sensors (EF) with servo control and parfocal zooming. Am I missing something?

“Crop” factors use 135/full frame as the metric.

The “Crop” factor vs 135 is 4:1 (36mm:8.8mm).

Against S35 (6k sensor) yes it’s closer to 3:1 (24mm:8.8mm)

Good Luck