PZ16-50 Barrel Distortion Correction

Started Nov 4, 2012 | Discussions thread
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Jawed
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PZ16-50 Barrel Distortion Correction
Nov 4, 2012

Here are some example barrel distortion corrections for the pancake zoom 16-50mm at its "advertised" 16mm setting.

I have used a raw file provided by DimitriDV:

http://forums.dpreview.com/forums/post/50175221

First, here is the picture without any corrections, from Lightroom 4.2:

unprocessed

Next, here it is with distortion set to 50. Then I exported to Photoshop and manually cropped. This has the full width of the original picture across the centre, i.e. it fully retains the two rows of pixels across the centre of the picture.

Lightroom 50 distortion + crop in Photoshop

Notice the change in aspect ratio.

Next, I used Hugin to re-project the uncorrected image exported from LR:

Hugin barrel distortion "b" correction = -0.041, Rectilinear

This is essentially the same as Lightroom's reprojection. The barrel correction I used in Hugin is slightly stronger. I asked Hugin to auto-size and auto-crop and set it to produce a low dynamic range non-exposure-corrected image.

Here are some other Hugin projections, all with the same barrel distortion correction:

Cylindrical

Equirectangular

Panini

Equirectangular Panini

In this picture I simply took the exported Lightroom picture into Photoshop, resized the canvas to make it square and then applied the Warp -> Inflate filter with -25%:

Photoshop Warp Inflate = -25%

Finally, for the lazy, in Lightroom you can choose the "Constrain Crop" option at the same time you set the Distortion amount. This produces a narrower picture, which appears to be about the same as the JPEG from the camera:

Lightroom 50 Distortion + Constrain Crop



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