Monkeying Around with Lens Calibration

I spent the best part of a day trying to create a lens profile for my trusty Canon PowerShot S90. In theory, it should be a rather straightforward thing to do. The Creating lens distortion models with Hugin’s lens calibrator article provides easy-to-follow instructions on how to create a lens distortion model.

Creating a lens distortion model with Hugin Lens Calibrator

I used a single RAW file to generate a simple model (see the screenshot above). I then added the following lens profile to the /usr/share/lensfun/compact-canon.xml file:

<lens>
<maker>Canon</maker>
<model>Canon PowerShot S90</model>
<mount>canonS90</mount>
<cropfactor>4.6</cropfactor>
<calibration>
<distortion model="ptlens" focal="6" a="0.01463" b="-0.07992" c="0.00461" />
</calibration>
</lens>

So far, so good. digiKam seems to pick the added lens profile, but the Auto-Correction tool (Enhance → Lens → Auto-correction) produces a rather strange result:

“Auto-correcting” distortion in digiKam

I can’t figure out what I’m doing wrong, so if you have a suggestion, feel free to chime in.

Freelance tech writer covering Linux and open source software.

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Posted in Open Source, Software
2 comments on “Monkeying Around with Lens Calibration
  1. garhol says:

    I’ll try this with some of the old lenses I bolt on to the SLR and see if I get a similar result.
    First thing I would try is with a different source image. Second thing would be to ensure that the focal length is being set correctly as it looks like the distortion may be correct but just an overly strong implementation.
    I’ll report back and let you know what success/failure I have.

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