CV Nokton f1.5/50 focusing problem

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Eric T

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Advice needed:
I have a CV Nokton f1.5/50 lens that was working fine up until today. I tried to use it today and it is out of focus below f8. Of course, at f8 or above, the depth of field allows the photo to be in focus.
I discovered this on an M8 but the camera is not the problem - other lenses, including a 50mm Summicron, focus well.
The focusing ring on the CV lens appears to move normally. All apertures are fine. The lens is clean.
When I focus the lens, the distance ring shows the appropriate distance.
Does anyone know what the problem might be and how I can get it repaired?
Many thanks and Happy Holidays!
Eric
 
Eric,
Was that the first time that you used the Nokton on the M8 when you discovered the focusing error?

I found that the M8 appears to be a very demanding camera re. registration of the lens.

Merry Christmas,
Uwe
 
Eric,

1.) focus at infinity and at something 1-2m away, confirmed with a tape-measure and tripod, and see if the lens focusing scale matches. If it does, the helix and RF mechanism are OK (they can get loose).

2.) take a lens cleaning cloth and see if the front element is loose. Or if the entire front wobbles. If the first is true, you can just tighten the front ring (with a rubber eraser, for instance). If the latter, you have to disassemble the lens.

The latter happens on some CV lenses, and BTW, on some ZM lenses as well (like Sonnar, Biogon and Planar - just saw your other post).

Best,

Roland.
 
Last edited:
If you have a film M body you can tape a piece of wax (food wrapping paper) to the film gate and focus on that to confirm if the focus is correct. Also you must be using a LTM to M adapter, is there any chance your using a different one lately?
 
Roland seems to have it right. The lens focuses to the right distance. The front wobbles. Tightening the rings does not seem to help. I will need to disassemble the lens. I have never done this before but would like to learn. I presume I begin by loosening the screws on the base of the lens.
If anyone can direct me to instructions on this, I will be grateful.
This is a great forum! Everyone is very helpful.
Eric
 
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