50/1.1 Nokton Backfocus

[Benjamin Marks]

I just recently purchased a C/V 50mm f:1.1 Nokton from a list member (thanks, Jason!). The lens arrived in beautiful shape. However, I can see that the lens is going to take some learnin' because of a backfocus issue: the lens focuses consistently behind the indicated plane of focus when used wide open and the amount of backfocus changes with the distance to the subject. C/V lenses are not alone in having this as an issue, of course. With a little practice, I was able to figure out the "nudges" for my most used distances with this lens (1-4 meters), but I think that any appraisal of the lens' obvious virtues must be balanced by an awareness that this is not a lens likely to easily reward careless use. I do like the image quality, which others have correctly (I think) compared to that of the 35/1.2.

In terms of other lenses and my RF's accuracy, I have a passel of lenses that work great on an M8 (50/1, 50/2, 72/2 etc.) However I am sending 4 lenses to Leica NJ next week to deal with w back-focus problem (50/1.4 Asph, 90 AA, 135/3.5 and 135/2.8).

I know that others have experienced this on this forum and elsewhere. Coping strategies anyone?

Ben Marks

 

[Benjamin Marks]

Yeah. I have got 20 lenses that don't. Also confirmed on an M2. The same lenses are off on the M2 and the M8. So: its the lenses.

 

[Krosya]

I do like the image quality, which others have correctly (I think) compared to that of the 35/1.2.

I know that others have experienced this on this forum and elsewhere. Coping strategies anyone?

Ben Marks

A couple of comments. First, (and I have never used CV 50/1.1, so it's all based on web images) I dont think that image quality from CV 50/1.1 is anything like CV 35/1.2. I do own a CV 35/1.2 and images I get from it are different from ones I have seen CV 50/1.1 delivers. Bokeh and just overall way CV 35/1.2 looks superior to my eyes.

Second. I dont recall reading about a Backfocus issue from CV 50/1.1 as much as - Focus Shift. Now that is a bigger problem IMO. Backfocus can be easily fixed by shimming, while focus shift cant.

Good luck!

 

[Benjamin Marks]

Will try to post some images over the weekend.

Ben

 

[Benjamin Marks]

Krosya: I have posted some images here:

http://www.rangefinderforum.com/forums/showthread.php?threadid=89441

I agree that the 35/1.2 has superior IQ overall. It is really an astonishing lens. I will have to use the 50/1.1 a while before I have made up my mind about it. Good thing that the process of making up one's mind about this sort of thing is so much fun.

In my case, while there may be some focus shift when stopping down, there is also backfocus. And the amount of back-focus appears to be different depending on the lens-to-subject distance. Unless I am completely confused about the terms -- which wouldn't be the first time. I was on the wrong side of the format-doesn't-affect-depth-of-field debate for years. ;-)