Back/Front focus regulation

[roshuu]

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Have any of you tried to correct problems focusing sticking pad or something on the lens? Can you advise something? My Voigtlander 40 / 1.4, has backfocus. Until now, I did correction manually (shift) ...

By the way - as previous owner cleaned matrix vacuum cleaner 1500W home, or it could result in some shifts the sensor? Or rather on the matrix will not be affected?

[roshuu]

I think, however, I found the solution: http://www.l-camera-forum.com/topic/13730-new-backfocus-thread-solution/

[lct]

Beware that this solution can render your rangefinder inaccurate with other lenses. I don't know if your CV 40/1.4 suffers from focus shift but it is a well known issue i warned you about if i remember well. You may try to calibrate the lens at the aperture you prefer though. My ZM 50/1.5 is calibrated at f/1.5 for instance. This way it is accurate at f/1.5 but focus shift cannot be fixed at other apertures this way.  

[roshuu]

I have one lens, rather soon nothing else to buy an. 40mm gives me a favorite 50mm field of view, that's enough for the M8.
I'll know how it went calibration.

[roshuu]

Beware that this solution can render your rangefinder inaccurate with other lenses. I don't know if your CV 40/1.4 suffers from focus shift but it is a well known issue i warned you about if i remember well. You may try to calibrate the lens at the aperture you prefer though. My ZM 50/1.5 is calibrated at f/1.5 for instance. This way it is accurate at f/1.5 but focus shift cannot be fixed at other apertures this way.  

 

Is such calibration is permanent? How long can remain without offsets? I will not change lenses, will be permanently Voigtlander 40.

[lct]

Is such calibration is permanent? How long can remain without offsets? I will not change lenses, will be permanently Voigtlander 40.

 

The calibration i'm referring to is not a body calibration but a lens calibration made by Cosina/Zeiss. It improves focusing at f/1.5 but cannot fix the focus shift at f/2 and above. If your CV 40/1.4 behaves like my  CV 35/1.4 SC, it is normally sharp at f/1.4-f/2 with serious focus shift at f/2.8 and above. Calibrating it at f/2.8 would render the lens sharper at f/2.8 and softer at f/1.4 & f/2 i guess but i have no experience with your lens. I would ask Cosina/Voigtlander to be sure.

[tobey bilek]

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If back focus behind subject and IF camera is correct,  you need to adjust the lens.  Likely there is internal adjustment or add/subtract shims.  This is proper way.

 

I have fixed a lens by cutting aluminum cooking foil , folding in half ,  and slipping between mount and lens.  You need to loosen mount .   This gives you around .001" increase.    Retighten using a star pattern,  i.e. 12:00,  6, 2, 8, 4, 10.

 

Use one round to just snug,  then round 2 a bit tighter, and 3 to original torque.   Check for smooth focus after each screw in 2 & 3  .  Uneven tightness will cause focus binding.  Use proper screwdriver.  They may be slotted, phillips, or JIT which look like phillips.  Micro tools .com.  Leica lenses are JIT #2.

 

I have also spray painted the back of the mount.  Two coats of black Krylon is .001"

 

Front focus is cured by removing mount  and thinning it with wet/dry paper, 400 grit , stuck on MDF board or float glass or marble surface plate.   You need a micrometer so you do not need to keep doing trials. 

[roshuu]

If back focus behind subject and IF camera is correct,  you need to adjust the lens.  Likely there is internal adjustment or add/subtract shims.  This is proper way.

 

I have fixed a lens by cutting aluminum cooking foil , folding in half ,  and slipping between mount and lens.  You need to loosen mount .   This gives you around .001" increase.    Retighten using a star pattern,  i.e. 12:00,  6, 2, 8, 4, 10.

 

Use one round to just snug,  then round 2 a bit tighter, and 3 to original torque.   Check for smooth focus after each screw in 2 & 3  .  Uneven tightness will cause focus binding.  Use proper screwdriver.  They may be slotted, phillips, or JIT which look like phillips.  Micro tools .com.  Leica lenses are JIT #2.

 

I have also spray painted the back of the mount.  Two coats of black Krylon is .001"

 

Front focus is cured by removing mount  and thinning it with wet/dry paper, 400 grit , stuck on MDF board or float glass or marble surface plate.   You need a micrometer so you do not need to keep doing trials. 

 

I wish you had no photos of this advice...