here is what Erwin Puts writes about the 1994-current (discontinued) Elmar 2.8
"2.8/50,Elmar-M, 1994
Introduced in 1994 as a special lens, only to be sold in combination with the M6J body, it has evolved into a normal , but underrated, catalogue item since 1996. Production however was continued during 1995. The image quality of this completely redesigned lens is amazingly good and now the position of the stop is between the second and third element. One might assume that the 4 element design has been fully explored and in a sense that is the case. Still the Leica designers could extract more performance out of the design, showing that improvements are always possible, . The ergonomics of the Elmar-M do limit its use. The external design very closely resembles the previous version, and inherits its small aperture ring and distance ring, presumably necessary for the compact size when collapsed. The lens mount is non-rotating.
At full aperture the Elmar-M adds medium to high overall contrast to the image. Fine detail is rendered crisply over most of the film area and fine detail is recorded with great clarity and sharp edges. This behaviour is interesting when compared to the Summicron (III) from 1969, at aperture 2.8. The overall performance is comparable, with the Summicron having an advantage in contrast. But in the field (zonal areas from image height 9mm) the Elmar has clearly the edge. The Summicron has better imagery in the centre (contrast and rendition of fine detail), but the Elmar records fine textures with greater clarity in the field. Stopped down to 5.6 or 8.0, the Elmar improves visibly with a higher contrast and consequently better rendition of (now) very fine detail. The fingerprint difference with the Summicron holds at these apertures too. Only in the extreme corners the Summicron has an advantage. Compared to the older Elmar, we see the progress when we look at the capabilities of recording fine detail, which is excellent with the new version and moderate with the previous version. Vignetting is more visible with the Elmar-M than with the previous version and identical to the current Summicron (IV), stopped down to 1:2.8. Close-up performance, even at full aperture is excellent with the Elmar-M, but less so with the previous Elmar-version. "