21/4 focus adjustment tips?

[sheepdog]

Hi guys!

I'm arguing a bit with my 21mm f4 LTM at the moment. It's focus travel has shifted relative to the scale on the barrel. When the scale shows infinity, both the focus patch and the images indicate 2m, and at the nearest setting, images and patch indicate 10cm or thereabouts.

I've taken the mount ring off, and found an adjustment mechanism with three set screws underneath. I'll try to adjust it this evening, but if anyone has any prior experience with this problem, I'd be happy for any kind of advise!

 

[ampguy]

I wouldn't worry about it. On this lens, 2m and infinity are just a smidgeon apart.

 

[35mmdelux]

If the elements move you'll be in far more trouble.

 

[ferider]

Hi guys!

I'm arguing a bit with my 21mm f4 LTM at the moment. It's focus travel has shifted relative to the scale on the barrel. When the scale shows infinity, both the focus patch and the images indicate 2m, and at the nearest setting, images and patch indicate 10cm or thereabouts.

I've taken the mount ring off, and found an adjustment mechanism with three set screws underneath. I'll try to adjust it this evening, but if anyone has any prior experience with this problem, I'd be happy for any kind of advise!

You are doing the right thing. The three black set screws have come loose. Re-adjust the ring, tighten the screws (you should see where they were, due to the black paint on the adjustment ring being gone a bit), and put nail-polish on the screws.

Haven't done it to a 21, but to a 35/1.7 and 50/1.5.

Good luck,

Roland.

 

[sheepdog]

Well, the entire optical assembly is mounted to the tube that these set screws lets you move freely relative to the mount, so dislocation of elements should not happen. Second, not being able to focus a 28FOV f4 beyond 2m (on my M8) is really more a serious defect than an minor annoyance..

I must say it's a clever design, but also that I'm REALLY tired of CV lenses having screws come loose. The 35/1.7 practically dismantles itself.. :-/

 

[sheepdog]

Yup. After loosening the black adjustment mount and setting the lens to infinity, I could just tighten the adjustment mount again to have a lens that focuses according to the patch within the specified interval. Puh. I suppose the 15/4.5 is the lens to get to fill the void left at 20FOV after the 21 became a 28FOV? 🙂

 

[Ezzie]

Where do you live? I´ve a 21/f4 if you need one for comparison.

 

[sheepdog]

Thanks, Ezzie! It seems all right after two days of use, but I'm in Trondheim if a local RFF meetup is ever in order 🙂