Summitar collapsible barrel issue

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crabface

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Hi all,
I have a couple of copies of collapsible summitars from the fifties (hexagonal iris). Both have stiff apertures which I think i am comfortable with cleaning and regreasing, but one copy, when the lens is collapsed, the barrel rotates freely (it locks fine when extended), on the other the barrel locks into place when collapsed and doesn't rotate. I'm assuming they should both lock?

Also on examining the rear assemblies, the inner threaded ring with 2 notches on one is flush to the back of the lens, but on the other copy (the one that rotates freely) it is screwed in further. Which is correct?

Otherwise they are both in good shape and i'd really like to get them up to snuff.

Many thanks for any assistance.
 
Just a probably obvious piece of advice. Be real careful not to trip the lens after you remove the front element. Got a Summitar pending for a trip to reattach the diaphragm blades :)

Best regards

Marcelo
 
Both lenses were tampered with. When collapsed, the lens barrel should not rotate. There's a guide machined into the barrel. The barrel is locked from turning once collapsed. The only way it can rotate is if internal parts are missing. They got the lens barrel out but then were not able to get it back in so they left the internal locking ball and spring out of the picture. Then of course it was easy to get the barrel back in. You see this a lot with collapsible Summicrons too, and they also usually destroy the felt bushing.

As far as the other issue with the slotted retaining ring, that should seat roughly 3-4mm down, as in img_2256.
 
Thanks so much! Yes i figured something must be missing. If the felt is damaged would that effect performance? Does it prevent light leaks?

I have a lens wrench on the way so will attempt to screw down the retaining ring.

thanks again for confirmation
 
No, the felt would have to be missing a chunk over its entire length for light to have any chance of leaking past the rear fixture. Generally, its purpose is to protect the chrome finish on the barrel and add a feel of resistance. I'd bet the felt bushing is still ok on yours. It's the Summicrons you really have to be careful with, as there are two guides machined into its barrel. The barrel has to be lined up and slipped back in just so to avoid damaging the felt.
 
As to the photos you provided.

I have a Summitar but do not have it to hand to check what I am about to say so I may be misinterpreting your images. But these images look to me like photos of the inner and outer helical rings. The two photos show remarkably different positions as you no doubt know. If one is positioned correctly that lens will focus correctly to infinity. But I would expect the other will not as this forward / backward positioning adjusts focus point on the helicals. You will soon know which is which by mounting the lenses in turn, taking shots and seeing which one focuses correctly (one most likely will not focus to infinity if my theory about these being helical threads I see in the images is correct). Unless of course both have been misassembled.

There is only one way to get this positioning of helicals right - by marking the position of them when they separate as they are disassembled. Which is what should have been done by whoever disassembled them before. My guess is this was not done with at least one of them causing it to be reassembled with the wrong thread starting point. Experienced technicians will normally mark that position with a scratch on both helicals at the point where they come apart as they disassemble the lens. And they should also measure using calipers or micrometer the distance between the back of the inner helical and the back of the outer one before disassembly (when the lens is focused at a known point - infinity or the nearest focus point are both OK). The measuring and the marking together will tell with certainty how the lens must be reassembled. If there is no scratch obvious on the inside of the barrels then trial an error is your only option using the "good" version as a guide as to positioning. There is a possibility that a scratch is present but if the person who last disassembled the lens did not also make the above measurement so they have aligned the scratches when reassembling but did so a complete 360 degrees out of alignment. This it would look right but the lens will still not function when put to use as infinity focus will be out.

If you have not done this before see if you can find some internet tutorial on how to disassemble and reassemble helicals - there is an indexing piece which rides in a slot which causes the inner helical to move up and down as you rotate the focus ring (which in turn is connected to the outer helical by screws). This indexing piece is what also means that there is only one right way to reassemble these parts. It's a bit hard to explain but pretty obvious how it functions once you have tried it a few times. It can also be frustrating as there are several starting points for the threads but only one is correct and you have to assemble the lens possibly multiple times and then test it by taking an image before you get it right.

You asked about the felt. If it the felt is worn/ damaged the lens barrel can be somewhat wobbly and lacking resistance till it is locked in the "taking" position. Once locked it should not present an actual image making problem as there should be no movement of the lens vis a vis the film plane / sensor. But I dislike wobbly lens barrels so it may be a little unpleasant to use but still functional. If you are disassembling the lens anyway you may be able to replace the felt with new felt of the correct thickness - which means more trial and error to find felt material of that thickness.
 
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