The 75/1.25 is fun at, and way better than most online reviews have stated. You must calibrate the RF Cam to your individual camera. You might want to set the lens to your preferred F-Stop when doing so. There is focus shift. I set mine for wide-open, use with a 1.25x magnifier on the M9. Great Choice.
Stopped down to F4. That should cover the Spectrum.
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50mm lenses- the Planar is a fine lens. However- the new Voigtlander 50/2 APO-Lanthar is "around" the same price. It is bigger, uses 49mm filters. It is sharp, amazing lens. All the latest in modern design in a lens.
This lens is amazing. You will not need a better-corrected lens than this. Unless you shoot UV. Then you need the lens on the Right. When received, I noted the overall size was about the same as my Pentax 85/4.5 Ultra-Achromatic-Takumar (UAT). The latter is 50 years old, maybe 40 lenses known...
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35mm: I went for the 35/1.7 Ultron in Leica Thread Mount. Use with an adapter. Aspheric design. "Classic" focus ring, not the 1950s styled ring of the M-Mount 35/1.7 V2. The Bokeh on the 35/1.7 Ultron is very smooth. Stopped down to F4: was measured at 90lp/mm (Line-Pair/millimeter). Not much difference in price between it and the 35/2.5. Also uses 39mm filters.
One of my favorite lenses. This is one of the original four lenses introduced with the Bessa R in 2000.
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LTM: I use this term to mean a lens in RF coupled 39mm thread mount that is Calibrated to the Leica standard. There are many 39mm mounts. M39 may not mean a lens calibrated to a Leica. There is the USSR Fed/Zorki mount which is 39mm threads, same28.8mm flange, but calibrated to the Zeiss standard. There is Zenit SLR 39mm mount. There is the Braun Pax 39mm thread mount with a different flange distance. There is 39mm mount for enlarger lenses.
So- ask any questions here about odd lenses. Not all 39mm mounts are the same.
I have a lot of lenses in Leica mount. Be sure to post a thread on "I want a Vintage Look Lens"....