Hallöchen! Bruno Postle writes:
> [...] > > The field of view and any calculation of focal length is correct — > when a, b & c are zero. Okay, clear. > The a, b & c parameters shift pixels radially, so pixels at the > sides of a landscape format photo will move. For example a 50° > landscape photo will occupy 50° of the output panorama; but if you > change a, b or c then the same photo might occupy 52° (or some > other value). (*) ... assumed Hugin's FOV value is fixed, right? In other words: Hugin's FOV is a representation of the focal length of the lens used in the undistorted lens projection formula, rather than the actual angle-of-view of the image. (I'm not criticising this, I just need to know.) > The a, b & c parameters are fixed to the narrowest width, so the > side pixels of a portrait photo _don't_ move. > > This does seem odd, but it is difficult to think of a lens model > where there is a simple relationship between horizontal and > vertical angle of view for anything other than a simple pinhole > camera. For an equidistant lens, it is simple. But for a pinhole camera, you still have the nasty tan() in the formula, don't you? > The panotools model has an advantage that you can use the same > distortion parameters for portrait and landscape images taken with > the same setup. This would also work if r_d = r_u * (a*r_u^3 + b*r_u^2 + c*r_u + 1), i.e. without the "-a-b-c", because by definition r_u is scaled to the shorter dimension, which is the same for portrait and landscape. Plus, this has the advantage that Hugin's value for the "focal length" would then represent the physically correct focal length of the lens. I still don't see the advantage of the fixed point on the long image edge. In Lensfun, it often makes autoscaling (to get rid of black corners) unnecessary. But even this fails often enough. That said, I'm aware this all this cannot be changed anymore. So actually, I only need to know (*). Tschö, Torsten. -- Torsten Bronger Jabber ID: [email protected] or http://bronger-jmp.appspot.com -- A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ --- You received this message because you are subscribed to the Google Groups "hugin and other free panoramic software" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/hugin-ptx/87d2gysmwo.fsf%40physik.rwth-aachen.de. For more options, visit https://groups.google.com/d/optout.
