Here's my lens inventory: 18mm super-elmar, 24mm lux, 28mm chron, 35mm lux (current version), 35mm chron IV, 50mm DR chron, 50mm lux, 50mm .95 nocti, 90mm elmarit and 135 apo-telyt. Most used are the 24mm, 35mm lux and the 50s and the 90.
There is a view out our dining room window which for about an hour each afternoon when it's sunny is a terrific brick wall torture test. I've included a sample below. I decided to run through the entire inventory at f4.0 - the fastest stop that works in sunny daylight - as a quick survey. If f4.0 is good then f5.8 and f8.0 are probably fine and f11 and beyond show effects of diffraction. I didn't do all lenses at all f-stops (as I have done with other cameras) because the amount of data simply overwhelms me. The idea was to do a survey then decide where to focus. I actually overlooked the 90 f2.8 - it was tucked in the corner of my carry around bag. I will be able to give it a close look toward the end of the week.
I will hold back any negative impressions until I've fully explored the lens.
The biggest surprise was the dual range summicron (I've had the close focus cam machined off so it mounts on a digital M). At f4.0 its shows no real softness in the corners, or for that matter any other bad characteristic. Overall the impression of acutance is slightly less than the Nocti at f4.0 but it's something that you would not notice except through side by side pixel peeping. The lens has a lovely signature - it or its cousin the rigid summicron were probably responsible for a majority of the iconic Leica images from the 50s and 60s (think JFK in the rocker with John John playing at his feet). From a "look" standpoint it mates beautifully with the MM.
(From prior experience the negatives are 1 meter close focus distance and some tendency to flare. There is a small amount of tame linear distortion that can be corrected in post if one desires to do so.)
So . . . I'll be exploring the dual range chron further for the next couple of days. I'll come back to the others in due course.
Here's the brick wall torture test and center and corner crops for the DR. I've included the crops because it's a little hard to believe that this lens does as well as it does.