In the age of large sensors in cameras such as the M10-R or SL-2, is it still OK to use older Leica lenses with such cameras? How about cameras with 24MP sensors? I know that my older lenses work will well with the M8 and the M9. Of course, old M lenses mount correctly on (say) a regular M10, but will I make good use of the 24MP snesor with lenses such as a Rigid Summicron or pre-asph Summilux or a 1936 Zeiss Sonnar?
Are we actually "losing" something when we use large sensor cameras or are we losing something when we use older lenses with such cameras? I do not think that I will sell my older lenses because I enjoy using them on any of my M mount cameras.
The answers to questions like these depend upon what you're trying to achieve. If you're looking for the absolute finest performance in your photographs, as measured by the specifications of resolution, lack of aberration, across the film plane illumination, lack of coma and astigmatism, etc etc etc, then you
must (and I use the term tongue in cheek) go with the very latest, best lenses made for the sensor recording medium.
If, on the other hand, you are looking to develop expressive photography to the best of your abilities and you
prefer (and I use the term with the same tongue in cheek intent as above) the look and feel of what your older lenses produce, with all their pleasant defects and aberrations, stick with what you have and see how you like it.
A higher resolution recording medium like the latest digital camera sensors will surface more lens defects, perhaps even to the point of calling them degradations, but it will also bring out the nice bits of the lenses that little bit more as well. Most of the stuff spoken in caveat about high resolution sensors and motivating anxiety about lens quality required, minimum aperture needed, shutter speed requirements for stability, etc etc, is just a bunch of hooey driven by some tiny grain of theoretical truth blown up into a big "OMG I need to buy everything NEW or I'm gonna get garbage!" hysteria. Equipment marketers love that thinking. LOL!
I use a range of Hasselblad and Leica lenses made from 1963 to the present on my Hasselblad 907x Special Edition's 2020 generation of the 33x44mm, 50Mpixel resolution sensor. And most of the lenses work very nicely indeed, warts and all, and look better than they did on lower resolution, older sensors. Newer models of the same lenses may indeed perform better, and the new Hasselblad XCD series lenses work best of all on this camera and sensor, but I'm not rushing to Ebay to offload all my beautiful lenses to buy one or two more of the XCDs any time soon. I like what I get out of the camera with these lovely old lenses.
Buy a body that you want to work with and try out what you have. Make decisions about what to keep and what to upgrade based upon what you see, not what others' opinions say. It's the only way to go, IMO.
G