I should say up front that esoteric or hard to find lenses are of minimal interest: time required, availability in the marketplace, and general subscriber interest don’t make for a synergy, but there are always special cases. Contact me with areas of performance or behavior that you think are worth exploring.
I’ve long wanted to do a 24/1.4 Summilux-M ASPH vs 24/3.8 Elmar-M ASPH evaluation having more to do with rendering style and versatility as much as sharpness since that is the real story for a lens that is ~3 stops brighter. That is now on the docket for later this month.
I am also poised to evaluate the 90mm f/2 APO-Summicron. However, I’ll be using the 90mm f/2 APO-Summicron-R ASPH using the Leica R adapter M (when the adapter becomes available)—the optical formulas for the R and M versions are the same*.
I own the R version and I deem it more attractive for its ergonomics and focusing range now that Live View on the Leica M Typ 240 is available. In particular, I much prefer the wide focusing ring to the outside and the aperture ring close to the camera side as well as the closer focusing distance of 50cm vs 100cm (neither is all that good at close range however).
* According to Erwin Puts in Leica Compendium, Second Edition, pg 550