Chapter: Lens Calibration
Overview
Lens calibration is one of the most frequently discussed topics in the community chat. It covers mapping the lens focus and zoom positions to real-world distances, configuring nodal offsets for accurate target tracking, and troubleshooting motors and calibration data.
Key Concepts
| Term |
Definition |
| 3-Point calibration |
Standard focus calibration using close, mid, and far focus points — works well for quality cinema primes |
| Lookup Table |
Multi-point focus calibration (up to 20 points) — used for non-linear or cheap lenses |
| Nodal point |
Optical centre of the lens — the point around which the camera must rotate for parallax-free moves |
| Front Nodal (X Nodal) |
Distance from sensor plane to optical nodal point of the lens — entered in Setups -> Lens Setup |
| Measure Optical / Z Nodal |
Offset from the arm's X axis to the sensor plane — tells Flair where the sensor is |
| Camera Mount |
New Flair feature (supersedes Draw Rig) — enters camera and lens positions separately; recommended for all rigs |
| FFT |
Focus Follows Target — focus driven by calculated distance to tracked target |
| FFO |
Focus Follows Object — focus driven by manually-entered distance, follows an exponential curve |
| FI |
Focus Independent — focus driven linearly by axis position; requires more keyframes over wide ranges |
| Field Distance |
Zoom calibration parameter — the distance at which the zoom calibration was measured |
| LENS.DBF |
File storing all lens calibrations: \Flair\FlairClassic\Configs\LENS.DBF — can be copied between PCs |
Scope
- Focus calibration: 3-point and Lookup Table methods
- Zoom calibration: multi-point table, blank-row trap
- Nodal point measurement (parallax test, trigonometry method, Flair auto routine)
- Target distance measurement (always from sensor plane, not nodal point)
- Focus motor: limits, hard stops, gear jump
- Probe lens calibration (Laowa, DZO, periscope/skater)
- Camera Mount vs traditional Lens Setup
- Lens calibration file backup and transfer
Focus Calibration Methods
| Method |
Use when |
| 3-point |
Quality cinema primes with linear focus ring |
| Lookup Table (up to 20 pts) |
Cheap/non-linear lenses, macro lenses, probe lenses |
| Real-distance input (no lens marks) |
Laowa Pro2be and other lenses with inaccurate markings |
Probe Lens Notes
| Lens |
Focus distance measured from |
Notes |
| Laowa (old models) |
Sensor plane |
Standard calibration applies |
| Laowa Pro2be (new) |
Front of probe |
Subtract probe length from distance readings |
| DZO X-tract probe |
Front of probe |
Same as Pro2be |
| Innovision Probe II |
Sensor plane |
Standard; use Camera Mount for periscope attachment |
Nodal Point Measurement (Parallax Test)
The most common method for finding the nodal point is the parallax test:
- Enter Carts View — Pan mode.
- Line up two objects (one close, one far) behind each other in frame centre.
- Pan (Carts Pan only, no track) until one object appears at the edge of frame.
- If the objects shift relative to each other as you pan — there is parallax. Adjust X Nodal offset.
- When panning produces no relative shift between near and far objects, you have the correct nodal point.
Dig's trigonometry method (2021-08-06) — for more precise measurement:
1. Start with pan perpendicular to track (90°). Line up two objects (near and far) in frame centre, both in line behind each other.
2. Store position. Pan and track until both objects are at frame edge and lined up again (use only Track and Pan).
3. Store second position. Calculate: nodal offset = Δtrack / sin(Δpan). Result is in cm.
4. Works for zooms at any focal length, and for anamorphics (pan and tilt separately).
Important: Failure to orbit around an object is almost always a measurement mistake or measure offset mistake — not a nodal point issue (Simon Wakley).
Issue Index
Official Documentation References