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title: "Zoom Calibration — Unused Rows Default to Zero and Break the Table" issue_id: LENS-zoom-calibration-blank-rows category: Lens Calibration issue_status: RESOLVED hardware: All rigs software: BOTH first_seen: 2022-04-01 last_seen: 2022-04-01 contributors: - Nitin (request) - Timothy Heys Cerchio - "~ ." (anonymous) date: 2022-04-01 search: boost: 0.8

Zoom Calibration — Unused Rows Default to Zero and Break the Table

CONFIRMED RESOLVED ALL RIGS BOTH

Summary

Flair's zoom calibration table has multiple rows for entering field positions, nodal points, zoom positions, and focal lengths. All unused rows default to 0.000. If these rows are not cleared before saving, the zero values corrupt the zoom curve and produce incorrect zoom tracking — especially visible when exporting data for CGI/virtual production.

Symptoms

  • Zoom tracking works for the focal lengths you tested but is wildly wrong at other zoom positions
  • CGI/VP lens data shows nonsensical focal length or nodal values at some zoom positions
  • Zoom Focus Follows Target fails at certain zoom positions even after careful calibration
  • New zoom calibration where you only entered 3 points but all rows appear "filled" with 0.000

Technical Background

The zoom calibration table stores a grid of values (focal lengths, field positions, nodal points) at multiple zoom positions. When Flair creates a new lens or zoom entry, all rows default to 0.000. The software interpolates between all rows — including any rows left at 0.000 — treating zero as a valid data point at that position. This distorts the interpolation curve between your real calibration points.

This is not intuitive: it looks like the rows are "empty" but they are actively used in the interpolation.

When it matters most

The 0.000 corruption is most visible when using zoom data for CGI export or virtual production, where precise focal length and nodal data at every position is required. For simple Focus Follows Target on set, the error may be small enough to be unnoticed.

Solution

Clear Unused Rows Before Saving

  1. Open Setups -> Lens Setup -> Zoom calibration and navigate to the zoom calibration table.
  2. Identify which rows you have calibrated with real data (your actual zoom positions).
  3. For all other rows (which contain the default 0.000 values): middle-click at the top of the column to blank out the entire column in one click, then re-enter only your real data points.
  4. Alternatively, manually clear each unused row by selecting it and deleting the value.
  5. Leave only the rows with real calibration data populated.

Timothy's shortcut

Middle-clicking at the top of a zoom calibration column blanks the entire column in a single click. Use this to quickly clear a column, then re-enter only the rows you need. Watch for the mouse tool-tip — it documents this behaviour.

If Zoom Tracking Is Already Wrong

  1. Open the current zoom table in Setups -> Lens Setup -> Zoom calibration and review all rows — identify which have real data vs defaulted zeros.
  2. Clear all unused rows (middle-click column tops to blank).
  3. Re-verify your remaining calibration points against physical measurements.
  4. Recalculate and save.

Notes

  • This same issue can affect the focus calibration Lookup Table — unused rows in that table also default to 0.000 and must be cleared.
  • For CGI/virtual production work, always verify zoom and focus table data against a focus chart and measured distances before export.
  • The Field Distance value in Flair 7's zoom setup should match the actual distance at which you performed your zoom calibration. The manual suggests 5m as a starting point but your lens and shooting distance will determine the right value.

References

Official Documentation

Bolt Quick Start Guide — p.65: Ulti-box Connector Summary — Lens, Focus and Zoom Ports

WhatsApp Excerpts

  • 2022-04-01 03:08 - ~ Marcin Biegunajtys: I’ll also post the trials and tribulations blog along with the insane amounts of junk food consumed to break the code! And a note to @Timothy Heys Cerchio knowing damn well not to bother the master, so that alone made me sweat enough to figure things out 🤪
  • 2022-04-01 03:56 - Ben Myers: Has anyone ever had any issues exporting fbx data where it switches to ‘motion builder’ as the coordinates right before it exports? I’m trying to send fbx 3 node maya y up to someone. I had zero issues last week but now it keeps switching on me.
  • 2022-04-01 23:49 - Gordon Eschke: Thanks Mike, that would be great
  • 2022-04-01 23:54 - ~ Nitin: Hello everyone. Is there a possibility for someone to make a video of a zoom calibration process.