BYTETOOLS

Lens Distortion Corrector

Straighten bent lines from wide-angle and action-camera lenses using the Brown–Conrady radial model, with a grid overlay for judging results.

Drop a photo with bent straight lines — architecture or a GoPro frameProcessed locally in your browser — never uploaded

What is the Lens Distortion Corrector?

Wide-angle and action-camera lenses bend straight lines outward — the barrel distortion that makes doorframes bow and horizons curve.

  • Brown–Conrady radial model, r′ = r(1 + k₁r² + k₂r⁴), inverse-mapped with bilinear or nearest sampling
  • Presets for mild barrel, strong barrel, fisheye and pincushion
  • Adjustable optical centre for lenses that are not perfectly aligned
  • Zoom control that crops the curved edges left behind by correction
  • Straight-line grid overlay on the preview only — the download stays clean
  • Radius normalised to half the diagonal, so coefficients transfer between photos

How to use the Lens Distortion Corrector

  1. 1

    Drop in a photo with lines that should be straight but are not.

  2. 2

    Pick a starting preset — mild barrel for a phone, strong barrel for an action camera, pincushion for a telephoto shot.

  3. 3

    Adjust k₁ until the bending is gone, using the grid overlay to check straight edges against straight lines.

  4. 4

    Use k₂ to fix the far corners once the middle looks right, and move the optical centre if the distortion is off-centre.

  5. 5

    Raise the zoom to crop the curved edges away, then click Download PNG — the grid is not included in the file.

About the Lens Distortion Corrector

Wide-angle and action-camera lenses bend straight lines outward — the barrel distortion that makes doorframes bow and horizons curve. Telephoto lenses do the opposite and pinch lines inward. Both are radial: the further a point sits from the optical centre, the more it moves, and both are described by the same short polynomial.

This tool inverts that polynomial. You set k₁ and k₂, the two radial coefficients of the Brown–Conrady model, and every output pixel is sampled from the position the lens would have put it. Negative k₁ fixes barrel, positive fixes pincushion, and presets for common cases give you a sensible starting point.

A grid of straight lines can be laid over the preview so you have something objective to judge the result against, and a zoom control crops away the curved edges that correction leaves behind. Radius is normalised against half the image diagonal, so the same coefficients mean the same thing on any photo. Every pixel is remapped locally in your browser and the photo is never uploaded.

Frequently asked questions

What is barrel distortion?

Barrel distortion is when straight lines bow outward from the centre of the frame, as if the image were wrapped round a barrel. It is strongest at wide focal lengths and is why action-camera footage makes doorways and horizons look curved.

Should k₁ be positive or negative?

Use a negative k₁ to correct barrel distortion and a positive k₁ to correct pincushion. Start around −0.08 for a phone's wide camera and −0.2 or lower for an action camera, then adjust while watching a line you know should be straight.

What does k₂ actually change?

k₂ scales with the fourth power of the radius, so it barely touches the middle of the frame and acts almost entirely on the far corners. Get k₁ right first, then use k₂ to pull in corners that are still bending the wrong way.

Why are there curved empty edges after correcting?

Straightening pushes pixels outward past the original frame, leaving nothing behind at the edges. Raise the zoom to crop past them, or set the uncovered area to white, black or transparent if you would rather keep the full field of view.

Does this replace a proper lens profile?

Not exactly. A camera-maker profile encodes measured coefficients for a specific lens at a specific focal length, while here you dial the two radial terms in by eye. For most photos the visual result is very close, but it does not correct tangential distortion or chromatic aberration.

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