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Simlar 5cm F1.5 Disassembly: Very Early Lens.
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PostPosted: Thu Jan 01, 2009 6:52 pm    Post subject: Simlar 5cm F1.5 Disassembly: Very Early Lens. Reply with quote

I "took a gamble" on a rare lens and camera on Ebay, one that had been in storage for many years. The Leotax arrived, with 5cm F1.5 Simlar lens and a Canon 85/2. Cosmetically, all were near mint. The Canon Aperture was inoperative- a quick disassembly and flood cleaning took care of the mechanism.

The SImlar was what I was really after. It turned out to be #74 of the series. This lens uses 39mm filters, unusual for such a fast lens. Found a photo of a later one, which had the retaining screws for the focus mount on the outside, like a Leitz LTM lens. This one went to F16 and had four retaining screws inside the mount.

And is was completely frozen.

Ronsonol to the Rescue. I let it soak for three days. After the first day, I managed to get the four retaining screws out. After the second day, "it budged". Today, It is "100%". I put the rear cap on the lens and filled it with lighter fluid, and a little machine oil. Worked it back and forth, added a little more machine oil. Once it was freely rotating, I used vacuum pump grease on the helicals for a nice, smooth motion.





Last edited by Brian on Thu Jan 01, 2009 7:00 pm; edited 1 time in total


PostPosted: Thu Jan 01, 2009 6:56 pm    Post subject: Reply with quote

This is a rare lens, and the formula is somewhat of a mystery. I've seen some state that it is a Sonnar formula lens, but after taking it apart I do not believe it. The surface behind the aperture is concave, not flat. The rear element is larger in diameter, more like a Summarit. It's longer than the pre-war SOnnar and shorter than a Summarit. Maybe an Ernostar? I'm not popping the glass out of their fixtures to find out. I will not risk re-assembly errors on this old and rare lens. Inside rear module, front section, front section split. Note the "10" inscribed on the parts. Is this the 10th lens that stopped down to F16? I've seen pictures of #17 that stopped down to F12.5.






PostPosted: Sun Jan 04, 2009 11:20 am    Post subject: Reply with quote

A happy new year Brian, and congratulations to your find.
Maybe a Primoplan type (5 elements)? The type was patent-free after the war.
Ernostars commonly have convex apertures behind the stop (and usually just one element). The power majority is before the stop and therefore, all Ernostars are prone to distortion. Also, there are usually as small as Sonnars, not bigger.
cheers, Frank


PostPosted: Sun Jan 04, 2009 3:29 pm    Post subject: Reply with quote

Thanks for the info! NOT an Ernostar. I've seen most people call this a Sonnar, and maybe one call it an Ernostar. I'm leaning toward it being a Xenon/Summitar derived lens. I'll be looking for "Summarit Swirlies", telling of a Xenon style lens.

I think this one has more than 5 elements, they could have split one from the primo-plan into lesser strength.

I am resisting the urge to pop the glass and find out. I do not want to ruin this lens. I've done some test rolls and will have them processed this week. We'll reverse out the design from the signature... Not via destructive testing!


PostPosted: Sun Jan 04, 2009 7:53 pm    Post subject: Reply with quote

I've got one! http://www.flickr.com/photos/10403737@N03/2173095705/in/set-72157603651363714/

I was told it was a sonnar design..hence the caption...since I'm not a rangefinder kinda person I've only used this as a close-up with a m42 camera.


PostPosted: Sun Jan 04, 2009 8:01 pm    Post subject: Reply with quote

It's interesting to see pictures of the Simlar 5cm F1.5- the design looks like it changed quite a bit. Mine does not have the two screws seen on the back of yours, I suspect the four screws on the inner rim of the mount serve the same purpose. I;ve seen pictures of an earlier one that went to F12.5, and a later one with a smooth rim and hat used 40.5mm filters. I wonder if the formula was changed sometime into the run.

I've got two test rolls in now. One with it on the Canon P, the other with it on a Leica IIIa. The Leotax is up for a rebuild. I will post on how the rebuild comes out.