B4 Lenses and the URSA Broadcast Camera

Good info Kim, thanks for taking the time to show us what was involved.

Thanks Joseph, this will help others ID the 1/2-inch lenses, that will Not fit, nor work on BM B4 mounts, and the lens projected image circle would be too small, if it did physically fit.
Cheers

Yes, they are hard to find. Try eBay, search for “B4 2/3rds rear lens cap”. If you need one, and can not find one locally, I will get you one and send it on. This is a 3d print cap made in USA, but it should work, cost is only $10, so no worries.
Cheers

Good, glad you got it sorted.
Cheers

That is because the Adapter is not completely optically corrected for the entire zoom range, unfortunately. The only ones I know of, outside the BM B4 mounts that are totally corrected, are the MTF Services and AbelCine optically corrected B4/MFT S16 adapters, which cost $1500-2500. You get what you pay for with special optical adapters like this. The B4 to PL adapter was originally even more expensive.

The BM B4mounts for the Ursa Mini and Broadcast camera work well. Rick has the original B4 Mount in the Ursa Mini 4.6 (PL) camera and uses a Fujinon Cine B4 Zoom on his camera at f/1.4 to 3.5 without issue, this is a X2 teleconverter snd Optical correction for the three color split, to correct focus to a single sensor.
The Ursa Broadcast is a X1.5 optically corrected teleconverter to cover the 1-inch sensor, and give the AOV as if it were a 2/3rds size sensor, kind of like the opposite of the Speed Booster.

The HD 2/3 B4 lenses work very well with both mounts, and are useable ag max f/stop, from wide to tell Zoom. I have the Angenieux HR 5.5x12 T/B4 Broadcast Zoom with Servo Zoom and iris control, and it works quite well on the Broadcast csmera from 5.5mm to its max at 66mm at f/1.4 and up, I get a nice sharp image. The only disadvantage is the B4 optical mount is longer than most adapters to be the FFD and optical correction, and adds several inches to the lens length, which most 2/3rds B4 lenses with the X2 Converter added to their rear, makes for a long bit of kit sticking out the front of the camera, which adds to balance issues, making the camera a little front heavy compared to a B4 ENG camera.

Being able to use the B4 Zoom wide open is important on the Broadcast camera and Micro Studio with their native ISO 200 sensors, iso 800 is OK on the Ursa Broadcast, but ISO 400 gives better results, with less noise, as you need the extra stop to compensate for the 1-stop loss the B4 Mount optical correction takes away. Having to stop down the lens to f/5.6 would kill the Ursa Broadcast for lower light shooting situations. So having a “spot on” optical correction in its B4 Mount is very important to allow using the B4 lenses wide open. Some of rhe better B4 SD lenses, like the upper end Canon and Fujinon zooms will also work, as reported by Daniel and Erik Naso.

That said, the Ursa Broadcast performance is even better when using the PL Mount and PL cine lenses, as you gain back the stop you loose, so iso 800 becomes more useable, and the lens choices become even better. Since it is a 1-inch sensor, many of the S 16 lenses will cover the spBriadcast csmera ‘s sensor. I have tested my Elite 9.5mm PL prime and the Angenieux 17.5-70 Cine Zoom. Also the Duclos Tokina 11-16 works well.
Cheers

Kim, I will see if Rick will measure and photo his UM B4 Mount and send them to you.
You would need a flange style adapter, that connects to MFT on one side, and has the lens mount flange on the other to take the B4 Mount. I have a couple prototypes of a PL/MFT adapter, thst has an adjustable “back focus” helix on it. I could send you one to play with, to see if it could be adapted to mount the B4 Mount.
Cheers

Thanks Denny for the detailed answer.

I have been thinking adapting one of the URSA B4 adapter to MFT, i.e. building adapter to attach it to MFT. Do you think it would physically fit?

I do not have one yet and from the pictures it is difficult to see.

The Ursa Mini adapters are designed to cover about 10.5mm horizontally, you’d need the assembly from the Ursa Broadcast. Is it available separately?

No, not as an accessory like the UM version Howard, as it comes with the camera, unless BM will sell you one as a spare part? But you are correct, forgot about the expansion difference of the image. The Broadcast B4 Mount would be the one to use. Another issue might be the difference in the Broadcast camera FFD compared to the Micro Studio, I can measure these two, next time I take the B4 Mount off.
Cheers

Hi - My first post here. You can add the Fujinon A17x7.8BERD-S28C to the list of lenses that are not compatible with the URSA Broadcast.

I bought the URSA Broadcast last week and I'm having the problem, that only iris can be controled from the camera or from an ATEM. The lens should support iris, zoom and focus control. This is an SD lens but already has the DIGI POWER function, so to my understanding, this is a "digital" lens and not an "analog" one, right?

Has anyone gotten a Fujinon SD lens fully working with the URSA Broadcast? Any chance, that a future firmware update could fix this problem?

Best regards,
Jakob

You can be glad, that at least iris control is working.

I think I’m DigiPower means or refers to this as digital Servo Zoom control, not that all the remote functions are digital vs analog. I believe it is still an Analog protocol controlled lens, as all SD ENG lenses were. Does the focus Servo control work from the camera, yiu do have the zoom and focus Servo selector on then lens set to “S” mode, which is Servo.
Without a ATEM connected, then see if the camera can control focus, by pressing the focus button, see manual:

Control and Playback Buttons
‚ Focus
When using a B4 or EF lens supports electronic focus adjustments, press the ‘focus’ button to activate auto focus. A white focus square will appear on the fold out monitor. Anything within the square will be correctly focused. When the lens is focused, the square will disappear.

NOTE To use the 'focus' button, your B4 lens must have servo focus control, with the servo activated. See the 'getting started' section for more information.

If this works, then the focus Servo is working.

On the ATEM, can you control any of the camera settings? Make sure you have a camera ID no set on the camera and the same number set on the ATEM, again check the UM Broadcast manual for details.

If everything is set correctly, and you still do not have control, contact BM Supoort directly. Also,see if yiu can get access to a B4 ENG camera, like a Sony or Panasonic, and see if the lens works on that camera, to double check the lens is actually working correctly. A lot can go wrong with used SD ENG lenses, while it may look newish, or not thst used, the Servo controls have mechanical systems thst wear out with use.
This is why, I stay away from any lens that is well used looking, and prefer to get newer ENG lenses, when servos are part of the kit, they do wear out. See Kim’s post above about lens Servo units.
Cheers

Thanks for the quick reply.

My ATEM can control any setting in the camera plus the iris of the b4 lens. I also have an URSA mini 4.6K and both are controled by an ATEM, so everysthing is working on that end.

I also contacted BM support and they basically directed my to this forum here to post my question as they think it is just a compatibility problem.

The zoom and focus servo selector are set according to the manual, and I have to following behaviour:

Iris:
Fully functional from camera and ATEM

Zoom:
Functional when using the rocker on the lens, not functional from the ATEM

Focus:
Not functional from the camera (pressing 'focus' doesn't do anything) and hence not functional from an ATEM. When I use the focus in manual mode and then switch the selector back in the servo mode, the focus moves automatically into 'middle' position, so it seems the servo is working and the lens somehow gets a signal that it should move into this position. If an analog protocol is used, I guess that the pin for iris control just gets a voltage applied, and that somehow seems to be the middle of the voltage range.

DigiPower means this is a digital Servo Zoom, not that all the remote functions are digital vs analog. It is still an Analog protocol controlled lens, as all SD ENG lenses were.

Do HD and 4K B4 lenses still use an 'analog' protocol or did they switch to a 'digital' protocol?

BM manual says

Analog B4 lenses with servos are also supported although the camera will only power the zoom servo and support electronic iris control

What does the term 'analog' mean here? Analog protocol or analog servos? As I'm experiencing exactly what's stated in the BM manual, my lens seems to be an 'analog' lens.

Of course I bought the lens used and can not verify, that there could be something wrong with the lens itself, though the store from which I bought the lens said, it is fully functional.

Fujinon A17x7.8BERD-S28C

Fujinon lens.jpg (279.18 KiB) Viewed 5678 times

Kim, the Ursa Mini and Mini Pro B4 adapter is set to cover about the 2K Window (about a S16 size) with some lenses, and the smaller HD window with all B4 lenses about a X2 mag.). The Ursa Broadcast B4 Mount, is set to a slightly wider X1.5 mag, to cover its S16 sensor, so about a 0.5 difference in magnification between the two, and a 1/2 stop more light loss on the UM mount.
Cheers