Blackmagic Forum

We have an URSA Mini 4.6k with the B4 adapter and the Fujinon XA20sx8.5BERM-K3 ENG Lens. When we change the iris from the switch, the camera doesn't adjust the iris smooth rather it steps the iris in increments. Its very noticeable. Anyone else experience this issue? Was wondering if this is normal for this camera/lens or if we are missing something in the settings. We can manually adjust the iris at the lens and it is very smooth.

Are you using a B4 adapter on the EF camera, or the BM B4 mount on the UM PL camera?
Stepping iris changes are useually an issue with the lens, or the remote control protocol, changing the Iris is steps instead of smoothly.
Cheers

This is the PL. The B4 mount doesn't work with the EF camera. This is the BM B4 mount.

Thanks, I know the BM B4 mount works only with the UM PL, and the new Pro. I was asking and referring to a B4 adapter (not BM) being used in the EF mount, since you did not specify which camera/mount.

I have not used a B4 lens with an ATEM, so I am nit sure if stepping VHS goes are a ATEM CCU issue or the lens? On a Sony CCU, the B4 lenses I have used, including a Fuji B4 SD lens, the Iris changes were smooth, no steps.
Cheers

hi,
any updates on this?

same problem here, using b4 lens, iris control works, but only in steps,
most worse, can not go down to 1.8, lens stops at 6.7.
that's a huge problem for low light scenarios ( which live production mostly is)...

anybody knows if this is a problem of the bmd camera to b4 lens,
or a software issue?

if tried all different parameters with the arduino shield,
no success.
rest is working fine...

Which B4 lens are you using! If the Iris is servo controlled, it may be the lens servo that is adding the stepped operation, like MFT lenses have. Also, you are not going to get f/2.8 out of a f/2,8 lensvwith the BM B4 mount, as you are going to have some light loss to the optical block that expands the image to cover the windowed sensor, you will loose about 1.5 stops of light. Somthe camera monitor will show the actual f/stop based on light transmission, rather than the actual f/stop on the lens.

?? Not sure that's correct Denny.

B4 iris servos are stepless. Any B4 lens on a proper camera will have smooth iris control from the CCU.

The issue is how BMD cameras work, they really are not working well for live production and are fundamentally a cinema camera.

I've given up hope of BMD producing a usable live camera system. They get close but the devil in the details makes them fall short of even a decent prosumer camera such as the Sony PXW200.


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thx for your replies!

the thing is, shouldn't it just control the full "physical" range of the iris motor?
by hand, i can still turn the iris ring further to the 1.8f, it is just via bmd control that it stops at 6.7f.

OK,Tom I agree, all B4 lens and servo control Iris that I have used are stepless on a Sony Camera, and when turned manually. I was just wounderimt if it was his lens servo motor causing the issue, not all B4 lenses in general, as he did not specify which B4 lens he is using. I know of other users using the B4 lens mount with HD B4 lenses with CCU control, not having this issue. I did not mean to imply that most B4 Iris servos did the step change he is experiencing. Your experience wi ENG cameras and B4 lenses is more extensive than mine. I was considering it may be an issue with the specific B4 lens the OP is trying to use.

Thanks for the added info.
Cheers

hi, lens is YG-18x9B4 KRS, Canon.

it works from the iris control on the lcd build into the camera (blackmagic ursa mini 4.6K),
but when connected to the arduino shield, it gets stuck at 6.something.
via camera, it goes down to 1.5f...

Ah, sounds like an issue with the Arduino Shield program, not the camera or lens. It really helps to have All the info up front.

Back to my original question. I have the URSA Mini 4.6k with the B4 mount and the Fujinon XA20sx8.5BERM-K3 ENG Lens. I have no problem going to wide open or closed with the iris via CCU. Our issue is this stepping. The iris is smooth in manual mode from the lens but steps when using CCU. Is this a camera issue? I was about to submit to BM support to see if I can get anywhere with them.

Can you control the Iris directly from the camera? If so, it is smooth.
If it is smooth from the camera directly (Iris button on the handle or camera buttons, then sounds like a CCU issue, if stepping on both the camera controls and CCU, could be the lens or the camera/Iris lens control interface. Hard to say.

Normally on an ENG camera, the Iris changes are smooth (no stepping). Tomsee if it is the camera or lens, you need to test the camera with a different lens, of the lens on a different camera and check the behavior.
Cheers

No control directly from the camera except f/stops. My manual control that I was referring to is simply turning the iris adjustment on the lens. Of course this will be smooth. We have 4 of these cameras and lens. No other lens to test with. I did send BM a support email. Below is the response from them.

"The stepping of the iris that you're experiencing is inherent to any electronically controlled B4 lens; there are pre-set f/stop points defined by the lens that the camera will be locked into. Essentially, these stop points will limit you to pre-defined iris settings when controlling the lens via CCU."

Sounds reasonable but no way to verify this. I sent Fujinon an email to verify.

Is this lens analog iris controlled or serial digital?

Analog should Be stepless at all times. I have no experience with serial digital lenses But it does feel strange that the iris wont Go stepless..

If I'm understanding the situation correctly, it is only stepping through preset values of f-stops, jumping from one to the next? Which command is being used on the shield to control the iris? There are three that deal with aperture. I am using Aperture (normalised) with a potentiometer and get a smooth response through the entire range. Whereas Aperture (ordinal) will step through specific options.

Hey guys,
I'm still having people asking me these questions, reporting these issues with stepping iris. It's really annoying, since we have on our side proven that none of our products have an issue with the resolution of values sent to the camera over SDI:
When the ATEM switcher sends iris values down the SDI return feed to the camera it happens are about the same resolution and range (0-2047) and of course this should span the full range of the iris capability as well as being stepless.
I was told by BMD this summer that a URSA Mini firmware upgrade might have fixed it, can anyone confirm this claim?
If anyone looks for a workaround, our SDI-B4 Link box will solve the problem using analog control.

On my analog lenses I feel like the stepping got much worse with the latest firmware. I hardly noticed it before.