Zoom Axis Unsmooth Motion - Calibration Points, Optimize, and Backlash¶
Summary¶
If the zoom axis accelerates abruptly, makes an unsmooth move at particular waypoints, or behaves worse than the focus axis, first inspect the zoom calibration curve and the physical backlash in the zoom drive. Community answers repeatedly point to fewer calibration points, the Optimize flag, and checking whether gear direction changes expose backlash.
Symptoms¶
- Zoom motion is abrupt or unsmooth at some waypoints.
- Zoom behaves differently from focus even when both are lens motor axes.
- Smooth waypoint move has a visible zoom kick.
- Issue appears when gear rotation reverses direction.
- The lens was calibrated but may have too many points or noisy marked values.
Settings Location¶
| Task | Flair location |
|---|---|
| Open lens setup | Setups -> Lens Setup |
| Edit zoom calibration | Setups -> Lens Setup -> Zoom Calibration / Zoom Linearisation |
| Inspect focus/zoom table curve | Setups -> Lens Setup -> View Table Graph |
| Enable curve fitting | Setups -> Lens Setup -> Zoom Calibration -> Optimize |
| Check axis limits/current scaling | Setups -> Axis Setup for the zoom axis |
Community Solutions¶
[LIKELY] Reduce The Number Of Zoom Calibration Points¶
Too many marked zoom points can create a wavy or reversing calibration curve, especially if lens barrel markings are not perfectly accurate. Use fewer reliable points across the range, then inspect the table graph.
Confidence: 0.82
[LIKELY] Use The Optimize Flag¶
Use Optimize in the zoom calibration / lookup table workflow to fit a simpler curve through the points. In one 2021 report, enabling Optimize cleaned up the move.
Confidence: 0.78
[LIKELY] Check Mechanical Backlash¶
If the bad section happens when the zoom gear changes direction, the problem may be backlash rather than fairings. Tighten/adjust the lens motor engagement carefully and avoid direction reversals where possible.
Confidence: 0.74
[LIKELY] Recalibrate The Zoom Axis¶
If the table is suspect, redo the zoom calibration from scratch in Setups -> Lens Setup -> Zoom Calibration. Blank unused rows and keep only meaningful points.
Confidence: 0.78
Evidence¶
| Timestamp | User | Evidence |
|---|---|---|
| 2021-03-21 | Simon Wakley | Usual cause is too many points and inaccurate markings; use fewer points, View Table Graph, and try Optimize. |
| 2021-03-24 | Anton Vikstrom | Optimize checkbox cleaned the move up nicely with a Cabrio zoom. |
| 2021-09-22 | Simon Wakley | Zoom calibration can be wide-to-tight or tight-to-wide; edit points that weave/reverse; 6-8 points often smoother. |
| 2026-05-18 | Michael deAnthony / Simon Wakley | Abrupt zoom acceleration; answer: is zoom calibrated, optimize it, otherwise probably backlash; reduce number of calibration points or use optimize flag. |
WhatsApp Excerpts¶
- 2021-03-21 12:02 - ~ Peter Constan-Tatos: It’s best to start with the rating plate on your robot. For example if it’s says 10kVA then the max current it will draw is worked out like this... 10kVA = 10000 = 1.732 x V x I V is the LINE voltage so 380, or 400, depending on your utility power and if you’re in the USA then it’s lower (about half) but that’s America for you 🙄. We have 380V here. Don’t confuse line with phase voltage. Line is phase-phase voltage and phase voltage is phase-neutral voltage. I know confusing! Just remember line...
- 2021-03-22 17:26 - ~ Anton Vikström: We're having a problem where the zoom axis isn't linear when we try a vertigo zoom. It pumps pretty aggressively. We've tried both the smaller and the bigger gears but the lens is smooth and not very stiff so that shouldn't be a problem, we didn't have time to test anything else but I'll be playing with it today, is there some setting I'm missing or something else that might cause this behaviour?
- 2021-03-22 22:52 - ~ Dan Gottesman: i like the regulator idea! and yes, both Arri and VR have 3-pin cables that work just fine. Red is the tricky one; they don’t accept more than 17v (or something like that)
- 2021-03-22 22:56 - ~ Simon Wakley: I’ve never had an issue with using focal length. The usually cause is too many points and the markings are inaccurate as it is a number not an exact line. Use fewer points. Look at the View-Table Graph. You can also try the “optimize” check box