Finally I have done the calibration for the Canon 15mm lens on a Canon EOS 5d slanted diagonally by 33.7 degrees. The calibration is done for an angle of 60 degrees (i.e. 6 pictures around). I haved used the method described by John Houghton at http://www.johnhpanos.com/epcalib.htm - 3. A DIRECT APPROACH - FOR SLRs ONLY.

Tilt angle (t) Correction (c)
7.5 0.7
5 1.0
0.0 1.65
-2.5 1.95
-7.5 2.55
-10.0 2.85

The straight line is described by c = 1.629333 -0.1232 * t
The correlation coefficient is r = 0.9998688
This is a very good correlation.

So there are two more calculated values:

Tilt angle (t) Correction (c)
12.5 0.09
-15 3.48

Viele Gr?º?üe
Carsten