Focus shift with Rollei 40mm f2.8 RF Sonnar?

[james_cooke]

I recently borrowed an RF 40mm f2.8 Sonnar and the shots taken at 80cm showed a

shift of focus of about 6 inches behind the set focus while Summicron/Rokkors

didn't show this. Just wondering if others notice this? Is it a trait of the

lens or this particular example faulty?

[andrewlamb]

I've got a screw thread version of this lens that I use on my M3. I'm never entirely sure what is

meant by focus shift but, at close distances, my lens has worked fine.

[raymond_tai]

6 inches sound pretty drastic to be focus shift. Mine focuses spot on.

[t_nu_tamm]

And my particular Summicron-C clearly showed focus shift while checking on the

groudglass. In "real life" it's a fine lens.

[jari]

I haven't noticed any focus shift either. But sometimes it's a bit tricky to focus at close distance with rf-version Rollei Sonnar 40mm/2.8 LTM/M on Rollei 35RF, because the lens can be focused to 70cm but the Rollei 35RF body can only handle 80cm.<br><br>

 

Here are the shots, which I have took with that lens:<br>

<br><br>

These were taken at close distance:<br>

http://www.flickr.com/photos/jsuominen/2150828227/<br>

http://www.flickr.com/photos/jsuominen/1569336159/<br>

http://www.flickr.com/photos/jsuominen/2139940115/<br>

http://www.flickr.com/photos/jsuominen/1498311553/<br>

http://www.flickr.com/photos/jsuominen/1487906522/<br>

[Mike Gammill]

It may be a backfocus issue. I remember reading something about backfocus problems with non-Leica M-mount lenses. The M-Hexanons and the Cosina-made M-mounts as I recall had some measurable backfocus discrepancies compared with the Leica lenses. With the 28mm focal lengths it was probably not noticable, but the 40mm it probably would be, especially at maximum aperture. In other words, the 40mm Sonnar should focus properly on the Rollei RF, Voigtlander, or Cosina M-mount rangefinders, but may not on the Leica. Konica Hexars I think may have had similar issues. I COULD be wrong, so treat this a theory, not a fact.