"f/256" wrote in message
. rogers.com...
Here is an example based on the Biogon 38mm:

Assuming it has a fall off as good as Cos^3

[...]
There are ONE and a HALF stops of fall off at the corners of the film with
respect to the center of the film!!

Funny, but I don't find the 38mm Biogon that bad in real life.