Blur Radius vs Blur Falloff ~ ISCO Westromat 50mm f/1.9

The ISCO Westromat 50mm f/1.9 is a unit focusing plasmat 6 element, 4 group formula lens. 

I've been looking at adapting certain kinds of somewhat difficult to find lenses to miniature format for soft focus work in using the first and second element separation control of the focusing ring to manage softness level.  However, I also have quite a stack of unit focusing normal 35mm SLR style lenses, and the brilliant little ISCO Westromat is one of them.  

While I am "on a roll" what better time to check two things about unit focusers with regards to potential soft focus work.  First, look at the bare lens wide open (I expect it to be sharp - it takes a lot to design a "bad" lens).  Second, look at what the effect of the filters might be on a very well corrected, sharp, not-at-all-bad lens.

Here's how to read the following graph. 

 

Comments ~

Only the Westromat/Nikon Nikkor Soft 1 combination falls within one of the two old soft focus lens zones.  All other combinations give varying blur radii outside of the old brass lens softness.

Looking at the Blur Falloff tells me that this will give a "fat" blur rendition (40% to 50% luminance measured half way between the leading and trailing edges of blur), even as the Blur Radii measured small compared with first element focusing lenses.  Wherefore I expect this lens used with Soft Focus Filters to deliver a different from Pictorialist softness "look." 

I'll have to spend some time with the ISCO Westromat to see how it behaves in the "real world." It may be just another excellent, sharp, boring 'ol 50mm plasmat that is indistinguishable from fully modern AF.  If that turns out to be the case, there'd be nothing wrong with that, right?