Guest #12 Posted March 4, 2012 Share #41 Â Posted March 4, 2012 Advertisement (gone after registration) Nope, see Lindolfi #31, the posted images give the 18 mm at 1m shift and #9 also not measured by me gives the 0.4m shift at 5m ... Â He gave the shifts as 25mm at 1m and 400mm at 5m in post 9. Link to post Share on other sites More sharing options...
SJP Posted March 4, 2012 Share #42 Â Posted March 4, 2012 He gave the shifts as 25mm at 1m and 400mm at 5m in post 9.Indeed 400mm is 40 cm or 0.4 m (and 25 mm is close enough to 18 mm - I was looking at the arrows in his pictures, which seem to read as 18 mm). Â Anyway, it does not essentially change the argument unless someone has numbers to the contrary. Â Determining the point of 'best' sharpness is not so trivial. More data gives better error margins. Here we are living with 2 data points which is somewhat marginal to say the least. Link to post Share on other sites More sharing options...
douglasf13 Posted January 23, 2013 Share #43 Â Posted January 23, 2013 I've been trying to figure out the shift of my newly acquired 50 Summicron Collapsible on my M9, which I didn't realize had noticeable shift issues. It seems that the lens is adjusted for f2.8, because f2 front focuses 10mm-ish, f2.8 is about right, and then the focus starts slowly going the other direction from f4 on, but just a little bit. This is all at mfd. Â I'd been reading reports of this lens not being sharp wide open, but, now that I've dialed in how to adjust for the shift at f2 (just a SLIGHT extra movement on the focus ring,) it is surprisingly sharp in the center. Outside of haze that needs to be cleaned in most copies, I'd imagine that many negative reports about this old lens wide open are because of these focusing issues. Â Full test image at f2: Â 100% crop: Link to post Share on other sites More sharing options...
TomB_tx Posted January 23, 2013 Share #44 Â Posted January 23, 2013 My '62 rigid Summicron also shows slight shift, and is also "spot on" at f2.8. Another lens I had (35 Zeiss) also seemed soft at f2.0, and indeed the focus was off. After correcting it is very good at f2.0. This may be a common issue. Link to post Share on other sites More sharing options...
douglasf13 Posted January 23, 2013 Share #45 Â Posted January 23, 2013 My '62 rigid Summicron also shows slight shift, and is also "spot on" at f2.8.Another lens I had (35 Zeiss) also seemed soft at f2.0, and indeed the focus was off. After correcting it is very good at f2.0. This may be a common issue. Â Yeah, between rangefinder calibration, lens calibration, focus shift and user error, I tend to take Leica users' (including my own!) opinion about lens sharpness with a grain of salt, because there are so many variables. This collapsible is certainly sharp in the center of the field from wide open, although the outer areas of the frame do require stopping down to sharpen up. Despite the focus shift, I like this little devil of a lens so much that I'm actually selling my version V Cron, because I'm not using it (although I can always get another one if I miss it too much, or maybe a Planar.) Link to post Share on other sites More sharing options...
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