Summary: The Leica APO-Summicron-M 90mm f/2 ASPH. is a nearly flawless telephoto lens for Leica rangefinder cameras. It's sharp from edge to edge and has a wide f/2 maximum aperture. Due to the price this is a big commitment and would be worth checking this Carl Zeiss Lens to compare: http://amzn.to/1wkakTh
Excerpt: Relative to Leica glass, this lens is a bargin. As a former Nikon shooter (>35 years)this is far superior to the 105mm f1.8 or the 400mm f2.8 or the Mamiya 250mm I previously used. I am blind as a bat and I can focus this lens without diaopter modification or magnification. Note: You will miss some images due to missing focus. This is a fair trade. The advantages over the DLSR & Lens size make this a big win for me, and the police don't interrupt me anymore.
Pros: Durable, Nice Bokeh, Rugged, Strong Construction
Excerpt: This is a wonderful lens...but my 90mm f/2.8 Elmarit is as good or better with definitely better bokeh....although the extra stop is worth having when you need it... And the admittedly very expensive Pentax 85mm f/1.4 FA* AF is better for real world IQ. Would I sell it? No....but IMHO it is not the best lens Leica ever made...
Pros: Consistent Output, Durable, Rugged, Strong Construction
Excerpt: I wanted to use this lens for portraiture with very shallow depth of field. After shooting some film and digital pictures with it, I'm also looking for other subjects that will be appropriate for this lens. I like it so much. It's tack sharp when you nail the focus at widest aperture. Only possible negative, and this isn't one IMHO, it is hard to get focus wide open as there's no margin for error.
Excerpt: Pros: - Great portrait lens with beautiful bokeh - Optical quality is excellent - Collapsible lens hood is practical Cons: - Even though this lens is marked as APO, there are traces of axial chromatic aberration - Focusing at f/2 with M9 is not always reliable due to shallow depth of field
Excerpt: This is an amazing lens and I'm surprised so little is written of it. It has a beautiful glow when opened up along with sharpness. It's a lifetime lens worth owning and keeping like a family heirloom. I love it on my M5 and M9. It' is not heavy by SLR standards. By rangefinder standards it is on the heavier side but light enough to have on my travel kit and the longer reach is great while traveling and the sharp rendition makes it easy to crop when necessary.
Pros: Consistent Output, Durable, Nice Bokeh, Rugged, Strong Construction
Excerpt: I think this is probably the best lens I've ever owned having been photographing for 27 years with many different types of cameras. This is a jewel that I'll always have. People say "heavy" but compared to an SLR lens it's not heavy. Yes it's heavier than the normal Leica Lenses at lower focal lengths.
Pros: Consistent Output, Nice Bokeh, Strong Construction
Excerpt: This lens is very large, and doesn't really "jive" with the compact M series theme. If you're into Luigi cases, it won't fit in the standard M9 nose (75/2 largest that will fit, but 90 will fit in the "Noctilux" nose). It is difficult to focus with the M9, even with the 1.4 x magnifier, and is my only Leica lens (out of 9) that I've sent back to be calibrated to my M9. Having said all that, its images, when in focus, are to my eye nearly flawless.