'..regarding Cron-R 35 and yes, it does weird things with sharpness circle! Indeed, the outer part/corners are in focus where the inner 2/3 circle is kinda soft. Now, did Leica screw it up or was it an intentional ‘reporter’ lens?'
'As with the Summilux-R the design goal was to achieve a very good performance in the central part of the image as this will benefit the intended type of pictures with this lens.
At apertures 4 and 5.6 the optimum is reached. The graphs of the 20 lp/mm and the 40 lp/mm are a bit wavy. At an image height of 12mm there is a weaker zone, the result of aberration compensation. The improvement beyond an image height of 18mm is the influence of the vignetting.'
~Erwin Puts.