@AurelieM

PARR stands for paraxial radial ray coordinate. PARR uses paraxial rays. In contrast, while its not specifically mentioned, I believe the Footprint diagram uses real rays. Could you try with REAR, real radial ray coordinate, instead of PARR and tell us whether it makes a difference?

Moreover, you might be interested in that thread as well, where I wrote a user-defined operand (UDOC) to read the actual min/max values from a Footprint Diagram:

The remark from @Mark.Nicholson still applies though, i.e. if you can get away with measuring the footprint with a native operand thanks to the symmetry of your system, then it will be an overkill to read the Footprint Diagram values via a user-defined operand (executing the UDOC adds some overhead to the optimization).

Take care,

David