|
in practice ...
In fact, if we pick CaF2 best possible practical match (K7), over the critical visual range (C to F line) we have the absolutely identical chromatic focal shift as FPL53-ZKN7 combo.
It isn't until we pick the widest theoretical possible choice (LaKN14 which is not practical for other reasons) that we get any meaningful improvement. But then we could use better theoretical match for FPL53 ...
(top left FPL53 - ZKN7 combination; top right CaF2 - K7;
bottom left CaF2 - LaKN14, bottom right FPL53 - LaKL21)
Bottom line, in practice there is no meaningful difference between FPL53 based doublet and CaF2 one.
Last edited by bratislav; 23-05-2014 at 12:25 PM.
|