Originally Posted by E. von Hoegh
My friend Eric Beltrando (visit his site www.dioptrique.info to see the results of his calculations) insists that Boyer Beryls (Dagor clones, and very like Dagors; Beryls, Beryl Ss, and Emeraudes all have the same prescription) cover 70 degrees and can be counted on for only 55 degrees in stringent applications, e.g., photoengraving.
People tend to see what they want to see, whether it is there or not.
Other makers' dagor clones are much the same. Between ~ 1912 and ~ 1950 Berthiot's coverage claims for their f/6.8 Perigraphe Ser. VIb shrank remarkably, from 95 degrees to 65 degrees. Same lens, different films and criteria of acceptable image quality. Coverage is a sometime thing but fantasy goes on forever.
Last edited by Dan Fromm; 04-30-2013 at 04:28 PM. Click to view previous post history.