Hi Aron On Jan 7, 11:01 am, Aron H <[email protected]> wrote: > On Jan 5, 11:09 pm, Tom Sharpless <[email protected]> wrote:>.... > > BTW one of the best treatments of lens calibration and correction I've > > seen is this article, brought to my attention last year by Michel > > Thoby:http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/37251/1/03-0869.pdf. > > It has a clear and thorough treatment of 'entrance pupil shift' and > > describes a parameterized ideal angle-to-radius function more elegant > > than mine. Needs serious study, but worth it. > > > Cheers, Tom > > Sorry I don't have time to go digest all of this discussion; hopefully > I will in the future. I just wanted to mention that two sources of > widely-used lens calibration are from Jean-Yves > Bouguet:http://www.vision.caltech.edu/bouguetj/calib_doc/ > and > OpenCV:http://opencv.willowgarage.com/documentation/camera_calibration_and_3... > The Caltech link includes a bunch of references and related links, and > IIRC justified using the even-power polynomials based on optic > characteristics, as well as numerical stability
Both of the package you refer to, like many others, assume a basically rectilinear lens (ideal pinhole model) and won't work for fisheye or extreme wide angle lenses. Such packages generally aim for much finer correction than is needed in pictorial photography, the goal being to measure the scene with sub-pixel accuracy. This perhaps justifies their narrow range of applicability. Gennery was not the first to design a unified calibration scheme for all physically realizable lenses, but he did a very good job of it. His main goal was surveying Mars stereoscopically through a pair of fisheye lenses, to a precision comparable to what could have been achieved with very high quality but uncalibrated long-focal-length lenses. PanoTools and Adobe Lens Profiles adopt the practical approach of separating lenses into two classes: 'normal' (rectlinear) and 'fisheye', and using a different calibration model for each class. Modern camera lenses have such a variety of projections that more than two classes might be justified. However the PT and Adobe calibrations work well enough in practice to satisfy most photographers. > > I discovered that if you limit Hugin to the 'b' parameter, and the > Caltech package to just the 'r^2' parameter, and scale the radial term > appropriately, they do indeed get the same answer - Caltech from > pictures of checkerboards, and Hugin from calibrating a 360 panorama. > Encouraging.... > Yes, that is what one would hope. However, 'b' corresponds to r^3... Best, Tom -- You received this message because you are subscribed to the Google Groups "Hugin and other free panoramic software" group. A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/hugin-ptx
