Fit additional correction: what coefficients it fit?

[dobedobedo]

Hi,
I notice that since version 1.6, p3 and p4 in camera optimization are removed, and a new option "fit additional correction" is added. However, I can't find much information about what coefficients this option enable to fit. In the 1.6.0 pre-release thread, I read someone said it is used especially for wide-angle lens.
May I ask which coefficients are used to enable "fit additional coefficients"? Is it just using p3, p4, or a totally different correction model?

Cheers,

[Alexey Pasumansky]

Hello dobedobedo,

These are not p3 and p4, but total different corrections which allows to compensate the distortions which cannot be fit by the ideal Brown's model used.