Hallöchen! Jonathan Niehof writes:
> [...] > > Absolutely YMMV and something to use with care. I found that even > with tuning parameters it was much faster than the manual method, > and I needed the contrast enhancement for my own eyes. And you really had only one fragment? (Sometimes this is only visible if you switch lines on and off.) > The manual method also seemed fairly sensitive to exactly how > careful I was in line placement (3 lines x 50 control point pairs > each takes a long time!) and tended to diverge badly at small > R. My thought (and you've been doing this a lot longer than I!) is > that it's worth getting some good data through the centre of the > image just to help anchor the fit there...otherwise degrees of > freedom in the fit will go into fitting little wiggles of the > periphery rather than keeping things reasonable at the > center. Limiting to poly3 may have the same effect for lenses > where that's appropriate. You are right in all points here. Therefore, I want that second line 1/3 from the centre. It can never be perfect, of course, because there's a tradeoff: Too close to the centre, and the deviation from a straigt line is too small to give senseful information. Too far away from it, and the centre cannot be extrapolated accurately. However, I don't see how the GUI tool helps with that. Besides, more than 50% of the images really cannot be detected automatically because the lines are interrupted and/or heavily blurred and/or dark. The only better method is a picture of an equidistant grid or rule, and taking the equidistance into account in the fit. But this is only feasible for tele lenses, given the minimal distance. > Incidentally, am I correct in assuming that despite the order of > operations in lensfun itself > (http://lensfun.sourceforge.net/manual/corrections.html), each > element of the calibration process is independent? I.e. I don't > need to have the correct distortion parameters in place to do > vignetting or TCA? Didn't look like it in the script.... Ordering is significant. Starting with the camera image, vignetting is corrected first. Then, TCA. Then, distortion. Therefore, the script can measure vignetting accurately in the raw image. TCA is also measured in the raw image, which is slightly inaccurate -- it should be vignetting-corrected first. But the dependece should be absolutely negligible since both aberrations happen on a very different frequency domain. And as for distortion, one should use only the green channel for control point placement. But life has to offer so much more than control point placement. ;-) Tschö, Torsten. -- Torsten Bronger Jabber ID: [email protected] ------------------------------------------------------------------------------ _______________________________________________ Lensfun-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/lensfun-users
