90/2 Summicron R repair

Lightshow · Joined: 04 Nov 2011 Posts: 3669 Location: Calgary

I'm having a bit of fun trying to open up a 90/2 Cron, I have most of it apart, but I'm stuck at the 3rd element from the front, it looks like I have to remove the hood to gain access to the rear of the front cell, only the slots are nearly inaccessible, they're blocked by the hood.
http://www.l-camera-forum.com/leica-wiki.en/index.php/90mm_f/2_Summicron-R

Anyone have some insights?

The lens has major water damage, the aperture mechanism is rusted tight, this is mostly for the fun of it, the lens cost me $40, I also have a 35/2 Cron that is worse, that one was $20.

dan_ · Expire: 2016-12-19

I don't have any experience with the 90mm Cron but I have opened the 35mm R-Cron. In fact I have remounted an optically perefect 35mm R-Cron optical blocks+diaphragm in a new custom-made barrel with a macro capable focussing helicoid. My beloved custom-made "Nah-Summicron 35mm" Smile

...

In short, I can tell you that the optical blocks, front and rear, and the diaphragm of the 35mm Cron are mounted in a inner barrel that can be extracted from the original exterior barrel containing the original focussing helicoid and diafragm ring of the lens. Once I extracted this "Heart of the lens" the front group can be unscrewed as a whole from it. The rear group is directly mounted in this inner barrel containing the diaphragm as well. The diaphragm unit looks like beeing encapsulated in this barrel and difficult to unmount. I didn't need to extract it.
In fact I didn't need to touch the block containing optics+diaphragm at all and therefor I had no lens alignment problems. I'm very pleased with the result - my beloved custom-made "Nah-Summicron 35mm".

I suppose that the 90mm Cron has the same configuration, with optical blocks+diaphtagm mounted in a inner barrel and with the diaphragm encapsulated in that inner barrel. This configuration ensures a high precision in lens alignment and diaphragm position irrespective of the rest of the lens body elements. But the downside is a heavier than normal lens (as all the Crons are).

I'd try to unscrew the front lens block as a whole and then to access the lenses it contains.

ZoneV · Expire: 2011-12-02

Funny, I have a Leitz 90mm/2 with heavy water damage as well. Mine is rangefinder version. I have all the glass out of the barrel as far as I remember, at the moment the iris housing is soaked in WD 40.