Use Your Camera To Capture "3D" Anaglyphs

Step 14 Post Processing To Remove Color Tinting Due To Vignetting

The artificial vignetting discussed in step 4 causes darkening and color tinting at the image edges. Any vignetting that remains will cause the left and right image edges to be colored with a bias toward the filter color on that side. For most scenes, quite a lot of vignetting can occur without an objectionable color cast; evenly-lit backgrounds make the edge casts much more visible. This can be corrected by creating a color-correction mask.

The color-correction mask is created by shooting a featureless white surface or grey card. Using a long exposure time and continuously moving the camera during the exposure will help even-out the image. Both the color tinting and darkening caused by vignetting will be captured in this reference image. If you are shooting in a linear raw format, the correction is essentially dividing by the reference image; the gamma used in JPEG images creates an exponential space, so divide becomes subtract.

This processing unfortunately does not correct the depth error caused by vignetting. A simple alternative that eliminates both the color cast and depth error is to crop the image to the center portion that does not have a color cast.