Nokton 50/1.1 focus shift

Brian Sweeney said:
Too bad no one ties the aperture ring to an indexed cam.
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It would probably be cheaper than a floating element and it should work really well as long as the problem is not dependent on the focused distance. I don't know if that's the case for the 50/f1.1 Nokton.

IMHO, the lens that really needs it is the current C-Sonnar 50/f1.5.
 
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I had problems with the F/1.1 also... but not only a shift when stopping down, it was just back focusing pretty badly wide open. I ended up returning it and getting the f/1.5 which has been a dream.
 
Can someone explain this to me: Does focus shift happen only when you focus on an object, for example at 1.4 and then stop down to say 2.8 while lens is still focused on original object?

OR, does the focus shift happen if I stop down to 2.8 first and then focus?

If the first example is true I am wondering why is this such an issue? Focusing is usually last thing I do before I press the shutter (after I set the aperture).

Maybe I am missing something here...:confused:

Cheers
 
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zvos1 said:
Maybe I am missing something here...:confused:

Cheers
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Yes, your rangefinder mechanism is not connected to your aperture ring, and neither are you focusing on a ground glass screen, so there is no compensation possible for aperture related focus shift. For instance on an SLR you could stop the lens down and then focus, gaining accurate focus even if the lens had focus shift. Not possible on a rangefinder.

As for the Nokton being unusable beyond wide open because of focus shift, I think that is a little unfair. Perhaps if you are a specialist in the genre of close focus fenceposts receeding into the distance it would be a problem, but f/4 is a great aperture for many things that fall outside this oeuvre.

Steve
 
250swb said:
Yes, your rangefinder mechanism is not connected to your aperture ring, and neither are you focusing on a ground glass screen, so there is no compensation possible for aperture related focus shift. For instance on an SLR you could stop the lens down and then focus, gaining accurate focus even if the lens had focus shift. Not possible on a rangefinder.

As for the Nokton being unusable beyond wide open because of focus shift, I think that is a little unfair. Perhaps if you are a specialist in the genre of close focus fenceposts receeding into the distance it would be a problem, but f/4 is a great aperture for many things that fall outside this oeuvre.

Steve
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Thanks Steve, I get it now. :cool:
 
The focus shift issues are mostly unavoidable on fast lenses without floating elements. However since the focus shift issue is at a definite amount, I usually will learn how much extra turn on the focus tab to get the precise focus on the F-stop I will use most. I think it is much easier than leaning back and forth.
 
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