Re: New 3D lens announced

Antonio F.G.

On Sat, Apr 10, 2021 at 04:41 AM, Olivier Cahen wrote:
Thanks for explaining how you can correct vertical disparities due to convergence of optical axes.
I wrote a paper to explain the alignment process used in the StMani3 program:

You can read just the first two pages that explain the approach: re-project the images of the unaligned stereo pair into a common virtual sensor plane. It explains there why any convergence angle can be corrected to null the vertical disparity, using just perspective transforms. You can skip the rest of the paper that tells the math process to find the virtual sensor plane.

Hey, only the vertical disparity can be corrected easily! The horizontal one is very other animal. I also talk about it in the document, and my best advise to correct a pair with the wrong horizontal disparity (either too much or too little), is to take your camera, go back to the place and shoot again taking care of the relationship between convergence, distance, stereo base, focal, et al:-)

For instance, it is not possible with StereoPhoto Maker.
I guess SPM surely uses the same approach as StMani3: Find the minimum error by successive approximations. (I do not know any other way). The approach requires to make an initial estimation of the solution, if the estimation is near the solution the process will quickly converge to the solution. If it is too far it will not converge, or converge a wrong solution.
SPM surely starts assuming the image pair is "reasonable", i.e. not excessive convergence or rotation. This may make it to fail if the initial convergence is too high. I guess it could perhaps be made to work by making an approximate manual alignment (the so-called "Easy Adjusment"), and a "Auto Alignment" afterwards (but I have not really tested this).

Have you tried Hugin? In spite it is not supposed to be made for stereo, JackDesBwa showed it is an extremely powerful aligning device, that includes at the same time stitching of several images into panoramas and lens correction (StMani3 does not deal with lenses nor panoramic's either). The biggest trouble is learning to use Hugin:-)


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