Cameras · Practical guide
B4 lenses for events: test iris, zoom and focus at rehearsal
A lens may respond from one control but not another, or lose focus as the shot changes. Before confirming camera coverage, reproduce the symptom with the planned camera, lens and controls. This guide shows how to organize that rehearsal and which model-specific references to check.
Describe the fault before changing settings
Ask the operator to repeat the action that revealed the problem. Record which control was used and what appeared in the image. If only an indicator changed, note that separately: the distinction helps the technician examining the equipment.
Use the table to choose a comparison. Fill in the results during rehearsal; no row by itself establishes that a component is faulty.
| Symptom | Comparison to make | What to record |
|---|---|---|
| Iris does not respond or jumps | Repeat the adjustment from one control at a time under the same light | Active control, previous settings, and image before and after |
| Zoom fails from one control | Compare the planned controls without changing anything else | Control model, cable, signal path and response |
| Focus changes during the zoom | Record a take that covers the required framing range | Position, distance, focus setting and point where focus changes |
Identify the camera and lens setup to test
Write down the full model and suffix of the lens, camera body and controls. Add any versions you can confirm and the path of each cable. A photo of the actual equipment can resolve doubts about which switch or connector is in use.
Save the initial state before making changes. If you compare another available lens or camera, record what changed in that setup too. Give the supplier a reproducible test when compatibility needs confirmation.
B4 iris: A/M and exposure
On URSA Broadcast G2, set a compatible B4 lens to A/Auto to accept iris commands from the camera. M leaves adjustment to the ring and does not accept those commands. With steady lighting, change the iris from the camera and observe both the aperture and the image. A enables remote iris control; automatic exposure is set separately. Do not force the ring while in A/Auto. Manual.
LA16 zoom: Lens and SERVO
On URSA Broadcast G2, connect the 12-pin cable to Lens and set the zoom switch to SERVO. Off air, compare the lens rocker with the planned control, starting from the same framing. If only one responds, record the control, cable and connection before changing the setup. Fujifilm lists SRD-92B for LA16x8BRM; confirm the model and its cable. In M/Manual, the lens does not accept zoom commands from the rocker or camera. Manual.
LA16: electronic back focus
The LA16x8BRM adjusts back focus electronically with F.f.; it does not use the external ring in the generic B4 procedure. Do this off air with the setup identified and a focus chart or high-contrast detail. The full procedure in the November 2025 URSA Broadcast G2 manual gives these steps.
Set up the reference
Place the chart or high-contrast detail approximately 70 feet away, or as far away as possible under the manual's instructions. Set zoom to SERVO and keep the camera fixed during adjustment.
Start the electronic adjustment
Hold F.f. for 5 seconds. Check that the rocker indicator flashes red; the lens will zoom to telephoto automatically.
Focus at telephoto
Focus with the ring. If Blackmagic Focus Demand is connected, the manual says to disconnect it to use the physical ring, or focus with the demand instead. Use the same method in the next step.
Focus at wide angle and confirm
Press F.f. again: the lens will move to wide angle. Focus and press F.f. to confirm; the indicator will flash red again.
Check the full zoom range
Move slowly through the zoom range and watch whether the chart stays sharp. If focus slips, repeat the start, telephoto and wide-angle adjustments, and confirmation before considering it ready.
Repeat the shots with the event lighting and distances
After checking the model-specific controls, rehearse the wide shot, lectern shot and close shot required by the program. Rehearse following a participant as they move, and save a sample. Note what responded and where in the movement the difference appeared.
If the lighting or position changes, repeat that portion of the test. Also review camera coverage to coordinate framing, supports and operation with the setup.
Check the program feed and recorded take
Keep an identifiable take and compare the same moment at the camera, in the program feed and in the file. Record where the defect appeared and from which position you observed it. That gives the technician a symptom they can reproduce.
If the difference appears when the stage lighting or a background screen is on, add the camera and LED guide to the test. For the file the editor will receive, review event recording.
Document the adjustment and open issues
Complete the lens section of the conference signal worksheet: setup, control, sample, change and result. Name who will review each open item and when the test will be repeated.
To discuss a proposal with GLMedia, share the program, floor plan, distances and available models. Ask about cameras and streaming with that information and the results you actually recorded.
Frequently asked questions
Is it enough that the lens receives power?
Test every function you need from the planned control. Record separately what responds and what still needs checking.
What should I test first if I do not know where the fault is?
Reproduce the symptom with the identified setup. Compare one control at a time and save the previous state so you can return to it.
Does the test end at the camera?
Save a take and check the program feed and file at the same point in the test.
What should I give the technician to reproduce it?
Full model numbers, confirmed versions, signal paths, initial settings and labeled samples. Explain what changed and what happened.
When should I repeat the check?
When the setup, position or rehearsal conditions change. Repeat the shots the program needs and update the worksheet.
Does the A switch on a B4 lens enable automatic exposure on URSA Broadcast G2?
A/Auto lets a compatible B4 lens receive iris commands from URSA Broadcast G2; it does not select the camera's exposure mode by itself. If you need iris-based automatic exposure, set it in the camera and test the response under the planned lighting. For a fixed iris controlled from the camera, use A and verify the commanded change without assuming exposure will adjust on its own.
What should I check if a zoom demand does not move an LA16x8BRM?
Check the demand model, cable and zoom switch. Fujifilm includes SRD-92B in its compatible accessories table for LA16x8BRM. For servo control, set the lens to SERVO and compare its rocker with the demand off air. If the rocker responds but the demand does not, record the difference and verify the connection before blaming the lens; receiving power does not confirm zoom control.
Should I adjust LA16x8BRM back focus with the ring from the generic B4 procedure?
For LA16x8BRM, follow the electronic F.f. procedure in the URSA Broadcast G2 manual. Start by holding F.f. for 5 seconds and confirm after focusing at telephoto and wide angle. First decide how you will focus if Blackmagic Focus Demand is connected. Then check the full zoom range; if focus slips, repeat the adjustment before using the lens at the event.
Sources and manuals
- Blackmagic Design — URSA Broadcast G2, Installation and Operation Manual, November 2025: B4 lens controls / Iris, p. 13. A/Auto and M modes; iris control from the camera.
- Blackmagic Design — URSA Broadcast G2, November 2025 manual: Zoom, p. 14. SERVO and M/Manual; lens and camera controls.
- Fujifilm — Control Accessories Compatibility, LA16x8BRM: Zoom Rate Demand SRD-92B; official page without a stated edition, accessed October 15, 2026.
- Blackmagic Design — URSA Broadcast G2, November 2025 manual: Setting back focus on Fuji LA16x8 BRM lenses, p. 17. F.f., 5 seconds, Focus Demand and zoom check.
- Fujinon 2025: LA16x8BRM-XB1A, p. 15