Blur Radius vs Blur Falloff ~ Steinheil Auto-Cassaron 50mm f/2.8

A friend pointed me to the Steinheil Auto-Cassaron 50mm f/2.8.  It's a Cooke triplet first element focusing 35mm SLR m42 mount lens and it's rather special.  It positively glows at all apertures and all subject distances.  These first element focusers can work magic by gently introducing optical imperfections as the first and second element distance changes.

Here's how to read the following graphs. Please keep in mind that these are for Full Frame digital.  APS-C is slightly different, as we may see in future posts.

 

 

Comments ~

The lens is soft overlaying sharpness.  At all apertures.  This seems to be Steinheil's design tendency.  

ISCO (the budget design house of Jos Schneider), Schacht, Roeschlein, Staeble, and of course Zeiss by comparison, are contrastier than Steinheil from wide open.

The Steinheil 45mm f/2.8 Cassarit and 135mm f/4.5 Cassar all show similar levels of softness that veil over a distinct sharpness.  Because of the rendition I feel Steinheil can be quite useful for working small format digital into early Pictorialist-like images. 

At this point I'm finding I have many good options from which to choose.  German.  Japanese.  Cooke triplet.  Zeiss tessar.  Steinheil Antiplanet (I have a Staeble 85mm that is of this formula).  All of these are good in one way or another.  I just have to work with them to see where I can go from here.