Found a Zunow, but inner surface is marred

[Vickko]

I found an LTM Zunow 5cm f1.1, but the inner surface is marred. It looks like the lens surface right behind the iris has been cleaned, as it looks like someone has taken a sandpaper sheet across the surface. I hope it is only the coating that is damaged, and that I can repair it.

So, does anyone know how to take apart the LTM 5cm Zunow?

I can only see three screws on this lens, at the iris ring. I am guessing and hoping that if I take these screws out, the ring slides back to reveal more screws.

Trying to twist the front lens group off isn't working, either the head doesn't twist off, or it is infinitely tight, or something is holding it.

The final thing is that the front lens retainer (and label ring) might need to come out to disassemble the lens, but I don't know of many lens designs where you have to take the front lenses out individually to get to the rear group. The designs I know, have the front group coming off, as a group.

Anyway, does anyone have experience with the Zunow 5cm LTM?

....Vick

[CameraQuest]

The Zunow 1.1's are exceptionally difficult lenses to take apart. Most experienced techs won't be able to disassemble it.

Stephen

[rlouzan]

Hi Vick,

Send it to John Van Stelton.

Regards,
RLouzan

[buzzardkid]

What Robert says,

John van Stelten at focalpoint (http://www.focalpointlens.com/fp_intro.html) is the man to get the job done.

Or, you can just donate it to me :p

[Vickko]

Hmmm, thanks Stephen. Do your tech's work on the Zunow? I love a good challenge. I'm travelling now, so the Zunow may become my "June/July" project.

Vick

[Vickko]

Update. After a discussion with John van Stelton, I'm likely not going to try this myself. e.g. from Clint Eastwood "A man's got to know his limits".

He did talk me through the disassembly - pretty scary in itself but not insurmountable. But he did tell me what I'm likely dealing with on that one inner surface, as he's done lots of them. Seems typical of Zunow 5cm lenses. No way to easily clean it off. He's done the successfully, but it is an enormous job.

So, I'll test mine some more and see if the surface affects imaging.

...Vick

[buzzardkid]

Let's hope it's stil usable, I'd love to see some shots from and with that lens, Vick!

Happy shooting!

[rlouzan]

Vick,

What did he say is the cause of this problem?

Regards,
RLouzan

[Vickko]

John says typically moisture, that gets on the surface, and the degradation just etches into the glass.

I just got a roll back and the images look fine. Not super critical testing, but on a bright sunny day, images are good, sharp, contrasty. Smallest diameter I went to was f8.

I'll need to do some fully open shots.

...Vick