DOF and pupil ratio

[enricosavazzi]

...
By the way, I measure my Luminar 16 mm f/2.5 as P=0.87 (exit pupil smaller). I wonder if the 25 mm is a different design, or is 1.1 using the other definition?
...
--Rik

They are somewhat different designs. The exit pupil of the 25 mm is visibly larger than the entry pupil. I believe the 16 mm adds an extra front (or rear?) element, so it is not a Cooke triplet like the longer focal lengths (I think I saw drawings of the Luminar lens designs on the Internet, but don't remember where). The exit pupil of the 40 mm f/4 is also slightly larger, while the pupils of the 63 mm are the same, as far as I can tell. I don't have a 16 mm.