How can I correct lens distortion in darktable if my lens isn’t in the Lens Correction module?

Question

I’m editing RAW (CR2) files in darktable and the images have strong wide-angle distortion. Normally I use the Lens Correction module, which reads EXIF data and applies the correct profile automatically, but this camera/lens combination isn’t listed.

How can I correct distortion in darktable when there’s no matching lens profile? Is there a way to determine or choose usable values manually?

user37649 · Accepted Answer

Unfortunately, as of right now, darktable doesn't have a very good way of doing ad hoc distortion correction for a lens you don't have a lensfun profile for. The following is a dirty hack that may be useful in cases where the barrel distortion at the wide end of a zoom is so strong that even "incorrect" correction might be an improvement...

In the lens correction module:

Click on the top (camera) dropdown list and select Generic --> Crop-factor 1.0 (Full Frame)
For the lens dropdown: Select Generic --> Rectilinear 10-1000mm f/1.0.
Change the geometry to fish-eye
Change mode to distort

Now, when you change the value in the "mm" dropdown menu, you should get different degrees of generic "defishing"; start at the largest mm values and work down the list until you find something that looks closest to correct. Clicking the circular arrow button to the right of the "scale" slider will auto-adjust the scale to the largest crop with no blank pixels.

If you're trying to correct "pincushion" distortion at the long end of a zoom, change the mode to "correct" instead of "distort".

How can I correct lens distortion in darktable if my lens isn’t in the Lens Correction module?

2 Answers

Your Answer

Related Questions