CV Skopar Color 21mm f4 screw-mount issue?

[mcf]

Hi

I bought the screw-mount 21mm a few months ago. Whilst I've not had much chance to shoot with it yet, the photos I have take are confusing me slightly.

Firstly, I'm not entirely sure infinity is actually hitting infinity in shots (end of focus ring infinity). This being on a rangefinder film camera.

And secondly, attached to a FujiFilm X-T1 (and tried on X-Pro 1) with an adapter, the focusing is just plain weird. It focuses very close, then no sort of mid-range focusing, and then infinity.

Can anyone confirm if they get the same sort of experience with this version of the lens? 😕

 

[Larry H-L]

No, that is not normal behavior for this lens. The C/V 21 f4 gets good reviews. I would have your favorite repair person take a look at it.

Does it rattle, if you shake it?

 

[kuuan]

Your description let's me suspect that possibly a lens element / block has become loose.
Not the LTM but my M version of the same lens had acted weirdly and produced bad results. In my case case the rear lens block had become loose, after tightening it all is back to normal.

 

[mcf]

No, that is not normal behavior for this lens. The C/V 21 f4 gets good reviews. I would have your favorite repair person take a look at it.

Does it rattle, if you shake it?

Haha, yes, I've just shaken it and there's rattling.

 

[mcf]

Your description let's me suspect that possibly a lens element / block has become loose.
Not the LTM but my M version of the same lens had acted weirdly and produced bad results. In my case case the rear lens block had become loose, after tightening it all is back to normal.

That sounds like the problem from the sound of the rattling, and would explain why sometime it's in focus, and sometimes it's not.

How did you tighten it? Remove the rear metal plate? I presume there's something under there that can be easily adjusted?

Otherwise, I'll make a trip to a repair shop.

 

[kuuan]

That sounds like the problem from the sound of the rattling, and would explain why sometime it's in focus, and sometimes it's not.

How did you tighten it? Remove the rear metal plate? I presume there's something under there that can be easily adjusted?

Otherwise, I'll make a trip to a repair shop.

right, I also believe that the behaviour you describe may well point to a loose optical element / group, rattling would confirm that but not necessarily must be detected.

in my case it was the rear lens group and to tighten it I did not have to remove anything. However mine is in Leica M mount, I don't know how the LTM version looks like but would think that it would be similar. Of course the loose element could be internal, requiring to open the lens.

the arrow points to the lens group, the full housing had come loose and that simply had to be re-tightenend
( the retaining ring of the single rear glass, a notch of it is seen right to the arrow, had not been effected nor touched )


CV4/21 by kuuan's lens tests, on Flickr

 

[mcf]

Great, thanks for the info. I'll check the lens at lunchtime when I get home and report back.

 

[kuuan]

welcome.
btw. as least as far as my Leica M copy is concerned, would I open it to check for loose, internal elements I'd not have to take off the lens mount but start by removing that same rear lens block indicated above. According to the lens' contruction that block holds 3 lenses, e.g. it could be that an inner glass has to be re-tightenend into that block. ( To access from the front there is a 'retaining ring' with typical two notches holding the very front glass. )

lens scheme can be seen here: https://voigtlaender.com/21-mm--f-4%2c0-color-skopar-p-typ.html