Late Wartime LTM 5cm F1.5 Sonnar, 15 years later

[Sonnar Brian]

I picked this lens up from Ebay 15 years ago, 2/2009. $170 or so, poor condition. It looked like it had been through the war, saw some rough times. 40% of the coating of the front element was rubbed off. The inner mechanism was full of grit. The helical was worn, and the barrel wobbled as you focused it. Could not be calibrated to the RF- that bad.
15 Years ago- took care of most of the issues.

So- in 2009, $170 got you an original LTM 5cm F1.5 Sonnar that looked like this...

 

[Sonnar Brian]

Lots of work 15 years ago. I used Vacuum Pump grease to tighten up the helical, but did not stop the wobble. I made a sleeve for the RF cam, part of the inner helical, to move through, kept it aligned. I used mylar tape. 15 years later- still good.

 

[wlewisiii]

Yeah, but my $170 in 2009 would have need how much more $$$ for a qualified tech like you to do the massive amount of work to resurrect that sad abused lens? Much better that it ended up on your bench in the first place!

My spanner will be here on Saturday, according to tracking so I'll get brave with the Super Takumar 50/1.4 and that's about as much as _I_ can handle! 🤣

 

[Sonnar Brian]

SO- here we are in 2024. I replaced the front element with one from a 272xxxx Contax mount lens that I picked up in a trade. The middle triplet and rear triplet had some haze. SO- made the best lens out of two, and performance on the worst lens does not change much. No change to the shim on the LTM lens. Name ring out, swap elements- done.
The front element is near-perfect. The glass is now as good as my 272xxxx LTM lens, which is near perfect. Slight misalignment on the aperture. After years of working on these basket case lenses, sometimes you go for the 95% solution. Focus is perfect, barrel is in tight, forcing it will break it. The helical is held in the mount with one set screw. I used plumbers pipe-fitting "goo" to tighten up the threads for the helical to screw into the mount. They were also worn.

 

[Sonnar Brian]

First two wide-open, last is at F4.
Focus via the RF of the M240, not liveview.


Wide-Open,

 

[Sonnar Brian]

F1.5 and F4 Pairs.


The Vacuum Pump grease (Dow/Corning) makes for a heavy focus, but it is slow and precise. Not a lens for the Skating Rink. You do what you need to do with worn-out helicals. I could remount this in Jupiter-3 mount for easier focusing. But- It works, I "Hacked it into working", and the results speak for themselves.

 

[wlewisiii]

No, not a Skating rink lens but it would make a wonderful early morning or late evening landscape lens. Beautiful work as always Brian. I love seeing these projects and wish I could find one like that for you to bring back to life like that, oh Master Jedi 🙏

 

[KoNickon]

Love reading these narratives. A master at work.

 

[Ororaro]

I have a similar sonnar. The loose/worn helicals are driving me crazy.
I used a super thick grease but it rendered the lens unusable. Now the grease has migrated onto the blades… but I still love the lens. Very unique and rare

 

[Sonnar Brian]

After 15 years- this grease stayed put. I also use a small dab under the aperture ring of the Sonnars to dampen the movement.

Pardon Our Interruption...

I chose Vacuum Pump Grease for the thickness, and does not outgas.

"APPLICATIONS : Sealing and lubricating chemical processing equipment, Lubricating plug valves, control valves, flow meter bearings, ceramic plug cocks, fire extinguisher valves, water treating equipment, synthetic rubber gaskets and seals in high temperature applications, Sealing vacuum and pressure systems, Lubricating O-rings in binoculars and telescopes and Preventing fogging of delicate lenses."

Interesting that the applications include optical applications.

 

[dexdog]

After 15 years- this grease stayed put. I also use a small dab under the aperture ring of the Sonnars to dampen the movement.

Pardon Our Interruption...

I chose Vacuum Pump Grease for the thickness, and does not outgas.

"APPLICATIONS : Sealing and lubricating chemical processing equipment, Lubricating plug valves, control valves, flow meter bearings, ceramic plug cocks, fire extinguisher valves, water treating equipment, synthetic rubber gaskets and seals in high temperature applications, Sealing vacuum and pressure systems, Lubricating O-rings in binoculars and telescopes and Preventing fogging of delicate lenses."

Interesting that the applications include optical applications.

I bought that product 10 years ago and used it on a 1943 CZJ Biogon in LTM that was badly worn because it was full of reddish sand that had eroded the alloy helicals. Works great and has not migrated.

 

[splitimageview]

Save the Sonnars!

Great work Brian.