Summicron 5cm f2 Collapsible - Question

[McGirton]

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hey! i'm new here and i have a question regarding the lens. i have received one yesterday, prime condition, one of the last collapsible ones, comes with a M Bajonet.

 

My question now is, when the lens is extracted, shouldn't it "lock in" somehow?? i pull the front of the lens out of the body and twist it to the left. all good, but when i want to change the aperture the lens moves easily to the right again. i can only work against that by slightly holding the lens in the front.

 

i am not sure how it was with my collapsible Summitar, but i can't remember it being like that.

 

thanks in advance!

[luigi bertolotti]

On my one (which is probably less fine than yours) it doesn't happen... not because the stop ring is "soft", but because, when you turn the front after extracting, is rather hard (but not in excess) to turn it back for collapsing : I think that both of those movements can be fine tuned by some lab... I'd say that the "balancing" of the respective softness/stiffness is the key to avoid the issue you quote: in my opinion (but am not sure) is easier to work on the stop ring movement than on the front securing mechanism, which involves machined components both on the lens' tube and on the focusing barrel; by contrast, the movement of the stop ring is usually rather easy to be accessed and maintained (it even seems to me to remember that in the forum we have seen some pictures about... there are good craftmens here... maybe right about the Summicron...)

Edited April 16, 2012 by luigi bertolotti

[StS]

I have the same lens, where the aperture ring behaves in the same way as Luigi's.

 

A simple fix could be to choose f/2 as rest position, the aperture ring will then be countered by the lens lock, when stopping down.

 

Stefan

[akiralx]

I had the same issue with the old Elmar 50mm f/2.8 where the whole front of the lens rotates, quite annoying.

 

As far as I know if there are two aperture scales (one on the top, one on the bottom) the lens is supposed to rotate as one will always be visible.

 

In the end I got rid of the old Elmar and got the new one.

[McGirton]

after some research i found an easy way to fix it:

 

"Take the lens off that camera, and look at the back of the lens barrel, the part that slides out, while it is in the collapsed position. There are three curved strips of brass along the rear edge. These three strips are what prevent the lens from unlocking. In some cases they have been pushed too close to the lens barrel, so they do not present enough friction to prevent the lens from unlocking.

 

Take a thin strip of plastic (I caution you not to use a steel knife, or a Swiss Army screw driver, as they can mark the brass), and gently push the end of the strips outwards, less than 0.2mm. Do this in increments and then try to lock and unlock the lens. It should work."

 

it worked great and now the lens locks like a charme and switching aperture isn't a problem anymore.

[gyoung]

I had the same issue with the old Elmar 50mm f/2.8 where the whole front of the lens rotates, quite annoying.

 

As far as I know if there are two aperture scales (one on the top, one on the bottom) the lens is supposed to rotate as one will always be visible.

 

In the end I got rid of the old Elmar and got the new one.

 

One of the 'joys' of using the original 2.8/50 (which have been doing for 40+ yrs) is that you have to remember to set the aperture before unlocking the focussing from infinity

 

Gerry

[luigi bertolotti]

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after some research i found an easy way to fix it:

 

"Take the lens off that camera, and look at the back of the lens barrel, the part that slides out, while it is in the collapsed position. There are three curved strips of brass along the rear edge. These three strips are what prevent the lens from unlocking. In some cases they have been pushed too close to the lens barrel, so they do not present enough friction to prevent the lens from unlocking.

 

Take a thin strip of plastic (I caution you not to use a steel knife, or a Swiss Army screw driver, as they can mark the brass), and gently push the end of the strips outwards, less than 0.2mm. Do this in increments and then try to lock and unlock the lens. It should work."

 

it worked great and now the lens locks like a charme and switching aperture isn't a problem anymore.

 

Good finding... ...a useful trick... I understand you operated on the three little "blades" along the black final part of the tube... I did not know it was only up to them the locking of the Summicron... I thought there was also an (invisible) milled guide like in the Summitar (see picture hereunder - Summitar at left, Summicron at right).

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[McGirton]

yes i was thinking that too! there has to be more to the locking of the lens but it's really just those 3 tiny blades.

[Felix66]

On 4/17/2012 at 5:38 PM, McGirton said:

after some research i found an easy way to fix it:

 

"Take the lens off that camera, and look at the back of the lens barrel, the part that slides out, while it is in the collapsed position. There are three curved strips of brass along the rear edge. These three strips are what prevent the lens from unlocking. In some cases they have been pushed too close to the lens barrel, so they do not present enough friction to prevent the lens from unlocking.

 

Take a thin strip of plastic (I caution you not to use a steel knife, or a Swiss Army screw driver, as they can mark the brass), and gently push the end of the strips outwards, less than 0.2mm. Do this in increments and then try to lock and unlock the lens. It should work."

 

it worked great and now the lens locks like a charme and switching aperture isn't a problem anymore.

Only answer and advice, that helped me to fix cron loose-locking issue. Thanks