[Klaus]

But is that were the case, one would see similar with every lens with a similar f-ratio. And we know that is not the case... Even the OP notes a difference between his 75mm f1.8 and his 50mm f1.8.

 

Do you have any ideas about how to do a quick and easy PF test? Then I could conduct some experiments.

 

There seems to be a relation to the angle of the light.

e.g. Fisheyes are especially prone to PF.

I am pretty sure that if a lens is prone to PF, it can be reduced by stopping down (at least on a fast tele prime).

 

A typical scene that pushes PF would be a something with sparkling water - e.g. a fountain or white water in bright sunlight.

Or stars ;-)