sorry for waking up an old thread. I'd like to use this method to calibrate a UW camera set-up. That is, a camera in a housing with a wide angle lens attached on the housing. Obviously this set-up is very much different from the camera on land so I need to do it in the pool, so I need to plan the exercise in beforehand.
The pool have a lot of natural lines to use in the tiles of the pool, the question is if these would be good enough, or if I must make my own lines using a little buoy with a weight and orange string to get enough accuracy? the purpose with the calibration foul be to be able to correct individual images using Fulla (and maybe directly in Lightroom eventually) but also to have a starting value when stitching linear panoramas of wreck sites. Cheers Oskar 2008/7/15 Tom Sharpless <tksharpl...@gmail.com>: > > Right on, Rik > > Rotating the camera to take multiple images of one straight line > target, then optimizing only the lens parameters, is a very clever > idea. You can cover the whole field of a fisheye lens without having > to build a circular target or worry about calibrated rotations. > > And it is perfectly OK if all the calibration lines are parallel, > because what actually determines the calibration parameters is just > the radial distances of the control points from the projection center > = image center + (d,e). So the important thing is to cover the range > of possible radii as fully as possible. For the same reason, the lines > need not extend all the way across the image; a little past center on > one side and all the way out on the other is fine. > > Cheers, Tom > > On Jul 14, 12:05 am, Rik Littlefield <rj.littlefi...@computer.org> > wrote: >> Erik Krause wrote: >> > The idea of using string lines is clever, but one must keep in mind >> > that a string line is never exactly straight. It's own weight always >> > bends it down more or less. The string tension must be very high in >> > order to be almost straight... >> >> Try using a plumb line, hanging vertical so the line will be perfectly >> straight even if it is not very tight. >> >> Take several pictures, rotating the camera so that the line appears in a >> numerous places within the frames, different distances from the center. >> It is not necessary to rotate around the NPP. >> >> Then optimize a single set of lens parameters across all frames to make >> all the lines straight, leaving pitch/roll/yaw locked at zero for all >> frames. >> >> This method tested OK for me a couple of years ago, but I have not used >> it a lot so I don't know what all can go wrong with it. >> >> --Rik > > > -- /O --~--~---------~--~----~------------~-------~--~----~ 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 hugin-ptx@googlegroups.com To unsubscribe from this group, send email to hugin-ptx-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/hugin-ptx -~----------~----~----~----~------~----~------~--~---
