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I am looking into using a GoPro camera for sail curvature measurements. For this the distorted fish-eye image needs to be transformed into a rectilinear image consistently.

I know solutions exist where the user needs to drag a slider until the defishing looks good, but that relies on the human eye. I would prefer a solution that relies on the lens and camera characteristics and hence would be scientifically valid.

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  • You can try photographing some building or box (something with straight edges) and defish until edges look right. you can then use the same ammount of "defishing" for all photos, even make a lightroom preset for it. – JoséNunoFerreira Nov 8 '12 at 16:53
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You could use the majority of software that handles barrel distortion, and just either setup a profile and save/reuse that profile, or reuse the settings by syncing the settings. An example of this software would be PTLens, but many solutions exist.

Since this is a fixed focal length lens, you don't need to worry about changing the settings for each image - they will stay constant across all images taken with the same GoPro.

To get the initial profile setup, you could easily shoot a test chart or a subject like a brick wall to determine the correct settings. I don't see any issue with relying on the human eye for this, it is quite easy.

We have many other questions on this site about barrel distortion(and vignetting which may interest you), take a look at this search: https://photo.stackexchange.com/search?q=barrel+distortion

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  • Thank you for the link to PTLens, I did not stumble on that program yet. But I hope I can find something that has a more numerical approach to it and eliminates the human factor. – Saaru Lindestøkke Nov 8 '12 at 21:54

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