Undistort
Introduction
Undistort solves radial lens distortion from a filmed lens grid. You shoot a calibration grid with the same camera and lens as your footage, the addon solves the distortion, and it exports ST maps so the correction carries into your compositing pipeline. It brings the industry-standard VFX distortion workflow into Blender, which has no built-in tool for it. It serves investigators and VFX artists who match renders to real footage and need corrected footage before tracking or compositing.
Key Takeaways
Grid-based calibration
Shoot a lens grid, and Undistort solves the radial distortion for that exact camera and lens.
ST map export
Export ST maps for native and overscan areas, so the correction works in your compositor.
Beta, Blender 5.2+
The plugin is in beta and requires Blender 5.2 or later. Older versions are not yet supported.
Installation
- Subscribe to the InLightVFX newsletter on the official page. The author emails you a download link. The plugin is free.
- Install the downloaded file in Blender 5.2: open Edit → Extensions, choose Install from Disk, and select the file.
- Enable the extension and open a scene. The workflow runs from the Movie Clip Editor.
Usage
Film the lens grid· same camera, same lens
Shoot the calibration grid with the same camera and lens as your investigation footage. Multiple frames improve the focal length estimate.
Open your footage· Movie Clip Editor
Open the Movie Clip Editor and load your main footage. The plugin works on the footage in this editor.
Load the grid· setup section
Open the Undistort panel and point its setup section at your grid footage so the addon can locate the grid in the frame.
Solve and apply· distortion
Run the solve, then click apply. Undistort corrects the radial distortion on your footage.
Export the result· ST maps
Choose the lens data you want to export, for example ST maps for the native or overscan area, and save the files for your compositing step.
In an Investigation
Lens distortion correction is a precondition for camera matching. Matching or measuring on uncorrected footage carries the lens error into every later result.
- Method section: record the camera and lens used, the grid setup (distance, framing), and the solve output (distortion values, ST map files).
- Decision log: note why grid calibration was chosen over a manufacturer lens profile, and which frames supplied the solve.
- Verification: re-run the solve from the same grid footage and compare the output. The ST maps and distortion values are saved files, so archive them with the case.
How It Works
Undistort compares the known geometry of the calibration grid with how the grid appears in your footage and solves for the radial distortion that explains the difference. More grid frames improve the focal length estimate. The exported ST map is a per-pixel screen mapping that carries the correction into the compositor, so downstream work uses corrected coordinates. In an investigation this matters because the correction is a computed estimate tied to your grid footage, not a fixed lens specification. That is why the method section records the grid setup next to the output.
Limitations
- The plugin is in beta. The author expects bugs and collects feedback by email.
- Blender 5.2 or later only. Older Blender versions are not yet supported.
- It solves radial lens distortion from your own grid footage. It does not read manufacturer lens profiles.
- The quality of the correction depends on the grid footage: same lens, stable exposure, and a clearly visible grid.
Resources
- Camera Matching, the technique that needs corrected footage first
- Analyzing Footage, where distortion correction sits in the analysis pipeline
- fSpy, the sibling camera-matching addon
Sources
- Undistort official page by InLightVFX, features, beta status, and newsletter download
- I made the VFX tool Blender was missing... (Full Workflow) by InLightVFX, the full grid-to-ST-map workflow
- InLightVFX on YouTube, the creator's channel