Ultron 28/1.9 not focusing properly on M8

[efix]

Hi guys, I have a problem.

I just acquired an Ultron 28/1.9, which, judging from its outward appearance, is in very good condition. No scratches, the lenses are clean, no dust etc. However, I won't get it to focus probably on my M8. It has ever-so-slight backfocus @ f/1.9 and 0.7m, which becomes increasingly heavier the further away I focus. Stopping down won't help until the depth-of-field becomes large enough to cover it, so I guess it isn't focus shift in that sense. Could it be the adapter? However, my Nokton 50/1.5 also goes beyond infinity as the adapter is the slightest bit too short, and still focuses dead-on at every aperture/distance combination. My rangefinder is also well calibrated, as I judge from both my Nokton and my M-Rokkor 28/2.8 focusing properly under all circumstances. Could I have a faulty lens? I also noticed that the lens body has slight play when holding it with one hand at the front and with one hand at the back - it's not absolutely firm (but again only very very slight play). Could it have been dropped and subsequently misaligned? I contacted the previous owner and am waiting for a reply. In the meantime, do you have any ideas about this? Any help would be highly appreciated!

 

[ferider]

Try a different adapter. Note that for a 50, variations in adapter thickness don't matter. For a 28 they very much do. The fact that back focus is there at all distances means your adapter is a tiny bit too thin.

Before buying a new adapter, you can experiment by adding a little teflon tape between lens and adapter and see what happens. BTW, what adapter are you using right now ?

Roland.

 

[efix]

Try a different adapter. Note that for a 50, variations in adapter thickness don't matter. For a 28 they very much do. The fact that back focus is there at all distances means your adapter is a tiny bit too thin.

Before buying a new adapter, you can experiment by adding a little teflon tape between lens and adapter and see what happens. BTW, what adapter are you using right now ?

Roland.

Thanks for that info! I've already done the experimenting bit. I noticed that when I screwed the lens outward up to the point where at .7m it would just hit the rf roller, I would then get precise close-focus. I made a little mark to both the lens barrel and adapter at the coinciding position, and then tried 1m, 2m and 3m. They were off again ... but it could be my experimenting had the famous human element that spoiled the results ...

I use the adapter the previous owner sent along with the lens, it only says "M39-L(M) (28-90)", nothing more. If the problem is indeed the adapter, which brand would you recommend?

 

[ferider]

Sounds like you got an off-brand Russian or Chinese adapter.

I recommend either original Leica or CV type II adapters. They do cost a bit more but are worth it, IMO.

Note that the Ultron's focusing can be adjusted quite easily DIY - but I do recommend to try another adapter first. It's a really great lens with very high performance (at its peak aperture of f4). Nice bokeh wide open, too.

Roland.

 

[efix]

Good news -- I introduced a slim piece of paper between lens and adapter, and this would seem to solve the problem! It didn't work for all distances, but much better than my hand-held attempt before.

Roland -- how can the Ultron's focusing be adjusted DIY? Not that I'm going to actually do it now, I'll first look for a CV or Leica adapter, but just out of curiosity.

 

[ferider]

The picture below shows a 35/1.7 but the 28/1.9 works the same. If you remove the mount, you will see a black ring held in place by screws. You can loosen those screws and twist the ring back and forth to adjust infinity alignment. It's a bit finicky, since you have to put the mount back on to try, remove it adjust again, etc. So don't do if not really necessary.

Cheers,

Roland.

 

[efix]

Roland, thanks!

Update: I now stuck some adhesive tape at either side of the lens mount, just enough to make the rear lens element touch the rf cam at close focus. It seem dead on now! Thanks so much for your help, I'm really relieved it's not a problem with the lens!

It's midnight now - I was going to be in bed two hours ago. But I couldn't have slept with this problem unsolved, anyway ... 🙂

 

[efix]

Try a different adapter. Note that for a 50, variations in adapter thickness don't matter.

How comes this? I would've though it matters for any lens if it's too close to or too far away from the sensor ...

 

[ferider]

Efix, because the RF mechanism (calibrated for 50mm) will compensate for it.

In other words, if you use an adapter that is thicker, not only will the lens move forward, but the lens RF cam, too, and what you see through the RF window is still correct. Works only for 50mm though.

Roland.

 

[efix]

Thanks, ferider - I have a vague idea of what you mean 🙂