Lens Distortion
Every real lens bends straight lines. Sometimes that is a look, sometimes it is a problem.
Creative Tool vs Technical Problem
Distortion is a feature or a bug depending on what you are doing.
Distortion as a look
Wide lens distortion is part of the wide lens character. A 14mm bulge makes a space feel huge; GoPro distortion is the action look.
No CGI? Correction is optional. Correct for neutral, leave it in for character.
Distortion as a problem to solve
The moment you track a shot or add CGI, distortion must be measured and managed. A distorted image does not show where things truly are, and VFX depends on exactly that.
Any composited element needs the distortion pipeline. Practical effects share the plate's distortion automatically.
What Does It Actually Look Like?
Distortion bends straight lines into curves. Try each type on a real frame.
You have a distortion demo in your pocket
Open your phone camera at 0.5x and point it at a doorframe. The straight edges bow. Switch to 1x and they straighten. That is barrel distortion, quietly corrected in software before you see it.
Why Distortion Makes Tracking Harder
A tracker measures where a feature appears on screen. It can only see what the lens shows it.
How Distortion is Handled in Post
Straighten the image, do the VFX work, put the bend back. The dinosaur is the CG element.
Start: the footage as shot
Footage arrives with whatever distortion the lens produced. It is measured first, with a lens profile or a chart shot on set.
Straighten the image (undistort)
The distortion is removed. Straight lines match the real world and tracking works. Resolve, Nuke and After Effects do this with a lens profile.
Add CGI in the clean space
CGI is composited against the straightened plate. Accurate geometry means everything lines up.
Put the bend back in (redistort)
The composite goes back through the lens distortion to match the original footage. Without this, the CGI looks too clean and straight.
Why Computer-Generated Images Are Different
Neither carries real lens distortion, for different reasons.
Zero distortion. By design. Needs some added back.
Renderers use a perfect mathematical camera: no glass, no bending. But real footage almost always carries some distortion, so a raw render looks too clean against it. The fix is the pipeline above.
Looks like distortion. Is not really distortion.
AI tools learned from real footage, so they imitate the look of distortion. But it follows no consistent geometry, shifts between images, and cannot be measured into a profile. AI video drifts between frames too.
Treat AI elements like hand-painted artwork: integrate with colour, grain and blur matching, not geometry.
Four Things Worth Knowing
Write down which lens is on which shot
A zoom at 24mm distorts differently to the same zoom at 70mm. Note lens and focal length for every VFX shot.
Shoot a grid chart
A flat grid shot once per lens gives VFX a precise distortion measurement. Two minutes on set, hours saved in post.
Use a lens profile, not your eyes
Correcting by eye is unreliable. Use the lens databases in Resolve, After Effects or Nuke, or your grid chart.
Correction is optional if there is no VFX
No compositing means correction is a creative choice. Know what you have and decide intentionally.