Hi Maik, On 31/07/14 07:00, Maik Riechert wrote: > first, a general question: Is a ptlens calibration with a=c=0 equal to a > poly3 calibration where k1=b? I was just wondering because I saw > separate code paths in mod-coord.cpp and I thought that poly3 could as > well just invoke the ptlens methods.
Yes, that seems right to me. > Now, the actual reason for my post is that I'd like to convert the > lensfun distortion calibration parameters to equivalent parameters of > the SIP model [1] used in astronomy. > > The main difference is that the SIP model is not based on radius but on > the x,y (unnormalized) pixel coordinates. For both the undistorted x and > y coordinates a separate polynomial can be defined with an arbitrary > order. It seems as if it's more general than the lensfun models, hence I > thought I could map them easily. > > So, basically you have x = u + f(u,v) and y = v + g(u,v) where u,v are > the original (distorted) pixel coordinates relative to the image center, > and x,y the undistorted coordinates. Therefore f and g have to provide > the amount to walk for each axis in pixels to get from the distorted > position to the undistorted one. I'm not sure if you've tackled the conversion between models correctly: the lensfun models as written transform from ideal to distorted coordinates, whereas you have written the SIP model as a transformation from distorted to undistorted. I found the Adobe documentation on their lens model quite helpful: http://download.macromedia.com/pub/labs/lensprofile_creator/lensprofile_creator_cameramodel.pdf There is also some archived discussion on this mailing list and in the Adobe forums that you might find helpful. cheers, Malcolm ------------------------------------------------------------------------------ Infragistics Professional Build stunning WinForms apps today! Reboot your WinForms applications with our WinForms controls. Build a bridge from your legacy apps to the future. http://pubads.g.doubleclick.net/gampad/clk?id=153845071&iu=/4140/ostg.clktrk _______________________________________________ Lensfun-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/lensfun-users
