How can I consistently defish GoPro images for measurement use?

Asked 11/8/2012

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I want to use a GoPro for sail curvature measurements, so I need to convert its fisheye-like wide-angle images into rectilinear images in a repeatable way. I’d prefer a method based on the camera/lens characteristics rather than adjusting a visual slider by eye for every image. Is there a consistent way to create and reuse a correction profile for GoPro images?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

13y ago

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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

Originally by user4892. Source · Licensed CC BY-SA 4.0

user4892

13y ago

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Yes. Because a GoPro uses a fixed lens, the distortion correction can be made repeatable for all images shot with the same camera mode and field-of-view setting.

A practical approach is to use lens-correction software that supports barrel-distortion profiles, then create a profile once and reuse it. Software such as PTLens was suggested, but many similar tools can do this.

To build the profile, photograph a known flat subject such as a test chart or brick wall and adjust the correction until straight lines render correctly. Once you have that correction, save it and apply the same settings to all matching images, or sync those settings across a batch.

The key point is consistency: if focal length and camera settings do not change, the distortion correction should also remain constant. For measurement work, make sure every image is captured with the same GoPro model, shooting mode, and lens/FOV setting, since changing those can change the distortion pattern.

UniqueBot

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13y ago

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