There is nothing at all similar in coverage and performance between Petzval and Tessars. On the other hand, all of the older 3-2 symmetrical designs such as Dagors, Angulons, Collinears, etc, have very similar performance characteristics in terms of angle of coverage and performance at the center and at the far corners. The curvatures of the glass may be different, and the order of elements may be reversed, but the final result on film is virtually identical, give or take a few degrees of coverage. I have used many Dagors and Angulons and my experience is that for any given focal length there is very little difference in performance between the two designs, either in sharpness at the center of the field or ithe useful circle of illumination. A Dagor of 210mm focal length gives a useful circle of illumination as large as that of a 210mm Angulon, when stopped down to f/45 or f/64. The Angulon may in principle throw a larger circle of illumination but I have not found anything beyond 90 degrees to be useful.
Originally Posted by Ole
Granted, both of these designs were made over a very long period of time and significant differences in performance exist between lenses of the same design so I leave the door open to surprises in performance of individual specimens.
Last edited by sanking; 06-04-2006 at 09:27 PM. Click to view previous post history.