Stereographic Correction of the Sigma 15mm DG Fisheye

This page provides Adobe Lens Profiles for converting images taken with the Sigma 15mm DG Fisheye lens into a stereographic projection. These profiles are suitable for use in Adobe Photoshop or Lightroom. The usual projection of this fisheye lens (and most others) is equisolid angle, which means that each pixel covers an equal solid angle. This has the often-negative effect, however, of compressing objects on the periphery of the image. A stereographic projection maintains angles, and often looks more pleasing.

Equisolid Angle
(Image courtesy Wikipedia)
Stereographic

The default lens profiles support only rectilinear correction, which preserves straight lines (i.e. a "normal" lens projection). Such has the disadvantage of causing significant stretching, and corresponding loss of resolution, on the periphery. A equisolid angle, stereographic, and rectilinear projection is shown on the following real world examples. I also show an example of stereographic correction, with the aspect ratio compressed to equal the original.

Original Image:
Uncorrected
Stereoscopic-Corrected Image:
Stereoscopic Correction
Stereoscopic-Corrected Image, Compressed to Same Aspect as Original:
Stereoscopic Correction, Same Aspect as Original
Rectilinear-Corrected Image:
Rectilinear Correction

Because the correction is implemented as a lens profile, one may see the effect of the correction directly in Lightroom while applying other edits. This profile was produced using a technique presented by user kenw in this forum post at Digital Photography Review, based on the geometric-distortion and chromatic-aberration parameters specified in Sigma's original lens profile.

To install, copy the lens profile into ~/Library/Application Support/Adobe/CameraRaw/LensProfiles/1.0 (on Mac) or [Home Directory]\AppData\Roaming\Adobe\CameraRaw\LensProfiles\1.0 (on Windows), then restart Lightroom. The archive also includes a set of develop presets:

  • Fisheye Devignette applies the Sigma-provided lens profile, and devignetting only (no distortion correction)
  • Stereo Fisheye applies both devignetting and distortion correction, but will require cropping (which is not supported in a preset) because the correction changes the aspect ratio of the image to make it wider than the original.
  • Stereo Fisheye Same Aspect uses the "Scale" and "Aspect" manual corrections to maintain the aspect ratio of the image, thus avoiding the need for cropping.

Download: stereo-fisheye-2014-09-30.zip

The files are free to distribute or modify. However, I would ask that you provide attribution both to this page, and to the original forum post, if possible.


Copyright © 2014 Christopher DeCoro