Lens stopper

[jaeger]

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7 hours ago, Harpomatic said:

I hear your point but I still think it’s making excuses. Relying on the stop is bad news? On a (supposedly) very high precision german engineering instrument? 

I too have in mind about German precision, so I made all these mistakes...  I don't recall Japanese lenses do this... maybe I'm wrong. 

Anyway, I naturally pop the dial all the way to test minimal focus and I freak out how bad it was.  Another scary thing is all lenses are different!  I had a moment thinking the sensor was off alignment because focusing at all distances are fine except the minimal.  I probably won't figure this out If not my 35mm lux is way off the chart (5-6 inches back focusing).  It made me check the distance reading on the lens...  Well, now lesson learned...

It's a user habit I guess, I don't read the distance and the only time I read those numbers in the distance dial is setting up for zone focusing. 

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[farnz]

23 hours ago, Harpomatic said:

They should stop where they are supposed to according to the focus scale - rack the focus to the MFD and you know where you are - or rather not, with Leica lenses!

You need to take temperature into account.  All metals expand and contract with changes in temperature and if the lens was set in the factory to stop at minimum focus on the focus scale then it would only be correct at the particular temperature on the day it was set in the factory.  The focus mechanism goes beyond the focus scale to allow for expansion of the metal and it's the same at the infinity end.

What always remains true is the triangulated focus point given by the rangefinder mechanism (providing that it's properly calibrated) so as long as you focus with the rangefinder or an EVF your pictures will be in focus across the focus range.

It's nothing to do with Leica being sloppy and I could suggest that the other brand lenses mentioned whose focus mechanism stops dead-on at MFD would be slightly off at different temperatures owing to metallurgical expansion and they look dead-on to you because your ambient temperature just happens to reasonably match the temperature in the factory when the focus mechanism was adjusted.

Pete.