Telephoto lens calibration

edit

Hi Everyone,

I'm working through lens calibration and I've been getting results that look fairly accurate with wider lenses. I've been using the following sample:

http://docs.opencv.org/doc/tutorials/...

plus: calibrationMatrixValues(...) to find the focal length. Then comparing back to the physical lens. With widers lenses I've only been about 2-3mm out, which could just be focus. But I've tried a 200mm lens and the calculated length comes back about 270mm (obviously wrong). Is there anyone that has calibrated longer lenses successfully and is there any calibration options that are worth trying or ways to set up the calibration that helps get a more accurate result?