I don't see how the lens is responsible for the camera's dynamic range, I am pretty sure that the Leica lenses for L are very very good and superior to the M Lenses on the SL Body, they were after all designed for the camera whereas most M-Lenses were designed for film bodies. It would be interesting to see results from the L lenses on other cameras especially film.
D,
I too was a skeptic, so I went to the Leica Store in SoHo. They had John Kreider the Leica "S" and SL Technical specialist on hand, and set up the rear of the store as a studio. I was the model.
It seemed like a rather moot exercise, but even without a calibrated monitor in a dimmed room the zoom in on a tethered laptop displayed mucho more shadow detail. Anyways this was where the enhanced dynamic range was clearly evident.
Using "S" glass on a SL seemed to me to be a very unpractical thing to do, but if I was a studio shooter who owned a Leica "S" system and had the glass...
BTW the rendering was mucho smooth. The lens utilized was a 100/2.0.
I owned a 50 Lux-M ASPH and traded it away. It seems the SL favors "R" glass and the rendering is to die for. Also I mount my 58/1.2 Noct-Nikkor on the SL which is really amazing. For a straight MF 50 I use a 50 Lux-R "E60" the last version 50 Lux that pretty much renders a lot like a Noctilux as far as the bokeh and OOF.
BTW I use the Noct-Nikkor on a Leica CL. With the crop factor the 58/1.2 becomes an insane 87/1.2. The Noct-Nikkor exploits the sweet spot of the lens and even at F1.2 any defect is cropped and is outside the perimeter of the sensor. Like in the Leica "S" glass demonstration the IQ takes a rather big step towards medium format IQ. I have the prints to prove it.
My 50 Lux-SL is not only big, but it is also the only native fast prime offered by Leica that is not APO. For the SL Leica will, eventually..., be making even all their SL Crons APO. These APO lenses also include wides: 35 Cron, 28 Cron, 24 Cron, 21 Cron.
I know it may be a long wait but it does seem like perfection will become available one day... eventually. These lenses will unlikely will be small like M-glass. In comparison APO glass for M's is very limited. I would expect performance to be in the realm of the Leica "S" glass demonstration, or like when I sweet spot a lens on my CL.
All this IQ likely does not matter to most people because they don't print, and if they do print it is of modest size or small.
Cal