Lens Distort Node

Every lens has optical distortion - more pronounced on wide angles (GoPro, fisheye) than on a standard 50mm. When you composite 3D CG over live action, that distortion is a problem: the straight lines of the CG do not match the curved lines of the shot.

The solution: Lens Distort Undistort on the incoming footage → you work on a "flat", distortion-free image → you composite the CG elements → Lens Distort Distort on output to give the curvature back to the complete result.

• Effects Library: Tools > Warp > Lens Distort
• Quick add: right-click in the Node Editor → Add Tool > Warp > Lens Distort

Barrel Distortion

Straight lines bow outward. Typical of wide angles (GoPro, action cameras, smartphone wide lenses). Most visible at the edges.

Pincushion Distortion

Straight lines bow inward. Typical of telephoto lenses.

Fisheye

Extreme barrel distortion. A "fish eye" look where everything is heavily curved, with a 180°+ field of view.

Anamorphic

Distortion specific to anamorphic cinema lenses (2:1 horizontal squeeze). The 3DE4 Anamorphic model handles it.

• Image Input (orange) - the footage to process.
• Effect Mask (blue) - optional. Limits the distortion to an area.

Complete VFX workflow:
MediaIn (GoPro) → Lens Distort (Undistort) → Camera Tracker → CG integration
                                                                  ↓
                                                  Lens Distort (Distort) → MediaOut

Simple correction:
MediaIn (fisheye) → Lens Distort (Undistort) → MediaOut
("straightened" image with straight lines)

Artistic style:
MediaIn → Lens Distort (Distort, custom parameters) → MediaOut
(add distortion to an image shot without any)

Mode

Undistort: removes the distortion, makes lines straight. Distort: adds distortion.

Camera Settings

Manual choice of the lens parameters, or connection to an existing Camera 3D (which already carries its settings).

Lens Distortion Model

• 3DE Classic: the standard model for most rectilinear lenses.
• 3DE4 Anamorphic: for anamorphic cinema lenses.
• 3DE4 Radial Fisheye: for extreme fisheyes.
• 3DE4 Radial: an improved radial model (more coefficients).

Distortion Coefficients

Technical values that define the distortion curve. Usually obtained through calibration (a checkerboard chart shot on set).

Edges

Canvas (black at the edges) or Duplicate (avoids blur artifacts in the other nodes downstream).

1. MediaIn - raw footage with distortion.
2. Lens Distort 1 (Undistort) - straightened footage, straight lines.
3. Camera Tracker / CG compositing - all the tools that need correct geometry work better on an undistorted image.
4. Lens Distort 2 (Distort, same settings) - redistortion to match the look of the source shot.
5. MediaOut - the final result with a believable composite.

Key point: both Lens Distort nodes must use exactly the same parameters. Full symmetry to avoid any drift.

• Undistort before the Camera Tracker - much cleaner 3D matchmoving on undistorted footage. It makes the solve error much lower.
• Undistort + CG integration + Distort - the classic VFX chain to integrate 3D objects into wide-angle footage.
• Correcting a GoPro shot for broadcast - an action shot filmed with a wide angle → Undistort for a "normal" look.
• Adding a stylistic fisheye - Distort mode with strong parameters for a skateboard, action sports or stylized POV look.
• Matching lenses between shots - a shot filmed at 50mm + a shot filmed wide → apply the same Distort on the 50mm to make the look consistent.
• Correcting matte plates - if a matte painting is flat and integrated into a distorted shot, Distort the matte so it matches the curvature.

• Calibrate with a checkerboard - the pro method: shoot a checkerboard pattern with your lens. Tools (Lens Cal, PFHoe) compute the exact coefficients to enter in Lens Distort.
• Identical parameters between Undistort and Distort - copy and paste them, or connect both to the same Camera 3D that carries the settings.
• 3DE Classic by default - fits 90% of standard lenses. The advanced models (Radial, Anamorphic, Fisheye) are for specific cases.
• Edges Duplicate for undistort - the corner of the image after undistort stays rectangular (sometimes with new invalid areas). Duplicate extends the image instead of leaving black edges.
• Straighten lines method - without a formal calibration, adjust by hand until the lines that should be straight are straight in the image.
• Preserving footage resolution - undistort can reveal black areas at the edges. Accept them or crop slightly afterward to clean up.
• Important for precise compositing - skipping the undistort is possible for standard 50mm shots, but crucial for GoPro, fisheye and wide angles.
• For professionally scanned lenses (lens files supplied by production), importing them directly through a Camera 3D lets you avoid manual calibration.