Using Voigtländer 25/4 with scale focus on Z-body

[MEPER]

The Voigtländer 25/4 (Snapshot-Skopar) is only fun to use if the m-scale can be thrusted. I used it with success on a Leica screw mount body years back. It created really sharp slides.
I tried it this evening on my Z50 via a K&F M39 to Z adapter. It seems this adapter (and probably other also) seats the lens a bit to close to the sensor to maybe ensure infinity focus.
IF I set lens to 1.5m it will focus at 3-4m distance.
I should be able to adjust using thin shims between lens and adapter (if I have any that fits. I doubt this).
I am quite sure that the lens itself is adjusted correct according to the M39 flange standard.
The question is if M39 to Z adapters exists that is 100% "M39 correct" or some has an option to finetune the flange distance?
If not any suggestions to fix the problem? 

[Birna Rørslett]

The adapters -- all makes apparently --  tend to be ever so slightly too short in order to preserve infinity focus.

For most lenses this poses no problems, unless the focal length is short as well. For IR the problem can be severe however, since these lenses get "near-sighted" and even on the native camera reach infinity at 1-3m on the distance scale. So, in that case, having too "short" adapters actually is welcome!!

My Voigtländer 21mm f/4 needed an internal adjustment, while the Skopar 25mm f/4 just barely   scrapes by without internal tampering. (both lenses in Nikkor S rangefinder mount). I use both for IR.

If the adapter is too short, add shims. Be sure to mark the adapter as modified.

[Akira]

I haven't used any M39 to Z adapter, but based on my real experiences with Nikon F adaptors to various mounts (Nikon 1, m4/3, Sony EF, Leica L-bayonette), the Japanese Rayqual and the German Novoflex adapters are the only ones whose infinity focus I can trust.

That said, based on my real experiences with these "trusty" adapters and F-mount lenses, I would have to say the infinity focus of Cosina/Voigtländer lenses are a little sloppy.  The infinity stops of all Nikkor MF lenses I've used (28mm, 50mm, 200mm and 300mm) were spot on, wheras those of Cosina Nokton 58/1.4 and Cosina/Zeiss Planar 50/1.4 are a bit off.

Considering that the accuracy of infinity focus is more critical for the lenses of shorter focal lengths, there may not be any mount adaptor that makes the distant scale of Color Skopar 21/4.0 trusty, unfortunately...

[MEPER]

If the adapter is too short, add shims. Be sure to mark the adapter as modified.

The shims you use are they thin M39 shims you put "inside" the adapter so adapter is disassembled?
You take out the M39 mount of the adapter and place shims between adapter "base" and the M39 insert?
If that is the case you could just use e.g. like 3 small spaces placed 120 degree around?
My first thought was to find thin M39 spacers and just place them between adapter and lens but then I wound not know where to get such M39 shims in various thin thicknesses?

[MEPER]

I found this tutorial how it can be done:
https://phillipreeve.net/blog/tuning-adapters-infinity-focus-reflections/

I have some metallic tape I can use. Will try to do something similar.

For the reflections I use matte black paint. Especially Pixco adapters are shinny inside. K&F a little better but not perfect.