Jupiter 50mm 1.5: Get one from someone that has used it on a Leica. A really good one is as good as a Canon 50/1.5, Nikkor 50/1.4, and Zeiss 50/1.5. Bad ones are muddy. My best luck is with the 1950s J-3's. Worst luck is with the 1980's lenses.
Nokton 50mm 1.5: Mine is from the 1950s, and you probably meant the modern one. The modern one is sharp and contrasty. The 1950s one is great. Slightly Swirly bokeh wide-open.
Canon 50mm 1.2: I like mine. Low contrast, very interesting Bokeh, sharp enough wide-open. Watch out for damage to the rear element. Canon used a lubricant that tended to run. It can range from haze to etching the glass.
Summarit 50mm 1.5: Buy one that has been recently cleaned, or budget for a cleaning. Soft wide-open, sharp at F4. Swirly Bokeh.
Nikkor 5cm F1.4: sharper wide-open, harsh Bokeh.
Carl Zeiss Jena 5cm f1.5 in LTM: uncommon, sharp, will run probably over $500 for a clean one.
Canon 50/1.5: faithful Sonnar formula lens in LTM, closer in rendition to the Zeiss lens. Getting Pricey! Same issue as other Canon lenses: watch for damage to rear element.
Canon 50/1.4: Planar formula lens, higher contrast, sharper than the 50/1.5. Bigger than the Sonnar lenses, uses a 48mm filter. Again: watch the rear element.
Nokton 50mm 1.5: Mine is from the 1950s, and you probably meant the modern one. The modern one is sharp and contrasty. The 1950s one is great. Slightly Swirly bokeh wide-open.
Canon 50mm 1.2: I like mine. Low contrast, very interesting Bokeh, sharp enough wide-open. Watch out for damage to the rear element. Canon used a lubricant that tended to run. It can range from haze to etching the glass.
Summarit 50mm 1.5: Buy one that has been recently cleaned, or budget for a cleaning. Soft wide-open, sharp at F4. Swirly Bokeh.
Nikkor 5cm F1.4: sharper wide-open, harsh Bokeh.
Carl Zeiss Jena 5cm f1.5 in LTM: uncommon, sharp, will run probably over $500 for a clean one.
Canon 50/1.5: faithful Sonnar formula lens in LTM, closer in rendition to the Zeiss lens. Getting Pricey! Same issue as other Canon lenses: watch for damage to rear element.
Canon 50/1.4: Planar formula lens, higher contrast, sharper than the 50/1.5. Bigger than the Sonnar lenses, uses a 48mm filter. Again: watch the rear element.