Ulrich, you taught me something. I did not know that there was a 'dual range' lens made by Leica. That is interesting. But to have a minimum distance of only 50 cm (or 20 inches in avoidupois) is not too impressive. A Takumar 'normal' focuses to less than one foot (about 30 cm). And it does that without having to switch to another mode. But, maybe there are reasons and justifications that I am unaware of. What you are referring to is this and is called a 'dual range Summicron': http://www.cameraquest.com/m50dr.htm
Call the upper part 'eyes' (!) according to this article. They provide parallax correction and allowing close focusing. I am not familiar enough to properly answer your question, Ulrich, but we both know that the scale focus on your lens should be the prime determinant as to what is in focus. Obviously, if you are getting a different reading in the viewfinder, something is amiss. The 'eyes' are mountable ONLY when the lens is focused closely (there is a dovetail preventing it from being mounted at further distances). It would seem to me that at the point of being able to attach the 'eyes', either there is a misalignment possible or the optical correction in the 'eyes' is off by a little.
This is probably the primary reason why I like SLRs more the RF cameras. What you see in the viewfinder is that which will actually manifest onto the film plane. Certainly, Leica is fully capable of matching the precision of any SLR, but ... the things that can go wrong in attaining this optimal situation are always threatening to downgrade this ability. To me, the actual optical 'readout' of an SLR is far more worthy of depending upon than the 'readout' provided by a lever (that could become inaccurate with time).
Sorry that I could not have been of more help.
PS: And if I may piggy-back onto your thread: Why is it that RF lenses do not focus as closely as those made for SLRs do? - David Lyga
Last edited by David Lyga; 04-27-2013 at 08:40 AM. Click to view previous post history.