Continuing my earlier discussion of lens corrections for pinhole cameras...
Here's a beautiful example of a camera with the pinhole at the geometric center of a curved film plane.
A traditional flat-film camera has no distortion (assuming a perfectly flat film plane and scan), but has significant vignetting.
This camera has no vignetting (left-to-right), but has significant distortion due to the curvilinear perspective.
It would be great if, in a future version of the specification, it was possible to correct asymmetric vignetting (controlling the X and Y axes independently) and if curvilinear perspective could be corrected to rectilinear.
Thanks for your consideration!
Upon further thought...
Asymmetric corrections for both distortion and vignetting within Lightroom/Camera Raw would be great -- but not necessary. Since these are inherently film scans and therefore TIFFs, and are a one-time predictable (zero-UI) correction, an external tool to be used before import into Lightroom would also work fine.
In other words, it may make more sense to think of this as part of the scanning workflow, since there are no curved digital sensors (that I know of).
Does anyone know of a tool which can correct for these sorts of projections on a TIFF? While I can do the math and can write a program, I have no clue how to do this one.
Just in case anyone was wondering...
I asked about this on the ImageMagick forum, we worked through the math, and today's release (version 6.7.0-8) has new algorithms to correct for distortions like this (it's -distort Cylinder2Plane). Like this one, that's a great community.
Next up, algorithmic vignetting correction (already possible in ImageMagick, but it could be simpler). Then it'll be a simple pass through ImageMagick after scanning before importing into Lightroom.