[en] Collimator scatter correction factors S_c have been measured with a cylindrical mini-phantom for five types of dual photon energy accelerators with energies between 6 and 25 MV. Using these S_c-data three methods to parametrize S_c of square fields have been compared including a third-order polynomial of the natural logarithm of the fieldsize normalised by the fieldsize of 10 cm². Also six methods to calculate S_c of rectangular fields have been compared including a new one which determines the equivalent fieldsize by extending Sterling's method. The deviation between measured and calculated S_c for every accelerator, energy and all methods are determined resulting in the maximum and average deviation per method. Applied to square fields the maximum and average deviation were for the method of Chen 0.64% and 0.15%, of Szymzcyk 0.98% and 0.21%, and of this work 0.41% and 0.10%. For the rectangular fields the deviations were for the method of Sterling 1.89% and 0.50%, of Vadash 1.60% and 0.28%, of Szymczyk et al. 1.21% and 0.25%, of Chen 1.84% and 0.31% and of this work 0.79% and 0.20%. Finally, a recommendation is given how to limit the number of fields at which S_c should be measured