Elmarit M 28mm (iii)

[AndreasG]

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Great description, very useful as a future reference in case of a repair, thanks!

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[seneschal]

Here's a picture of the lens body out of the focus mount again... have to say I am not convinced I have done a good job of taping and marking the point to which it needs to be screwed back in again!

The thread looks good, not cross threaded anywhere. So I just cleaned it to make sure and have discovered a point on the thread where there seems to be a deliberate section about 2.5 - 3cm long where there is residue of something that appears to have been "painted" into a single section of thread. It does not overlap into any other layer of the thread.

Could this possibly be some kind of Loctite or other material that was used to prevent screwing in of the lens body further than the adjusted calibration point. Seems a weird way to mount a lens, but I do wonder what it is and why it is there. I'd still secure it with a spacer or shims if it were me.

Please have a look at the marked up photo and if anybody knows... that would be really helpful to anyone who ever needs to mess with an Elmarit 28mm version 3.

 

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[luigi bertolotti]

2 hours ago, seneschal said:

 

There is no sign of any Loctite or other thread treatment, so I am convinced that there is a spacer, or shim of some kind missing.

 

 

That's my feel to... if you say that scale focus to 0,7 = real focus to infinity... this makes around 1,5mm of movement for a 28mm (roughly - but not wrong.. let'say +- 0,2, which is a big variation... probably one can find a precise value somewhere)  : anyway a measure that is consistent with some shim or spacer

Edited May 28, 2021 by luigi bertolotti

[luigi bertolotti]

Hmmm.. I saw your pictures after my previuos post... interesting... it makes me remember the coupling of the Telyt 280 lenshead to its focus unit (it too a "Canadian"  design) ... Isn't there an intermediate ring between the lenshead male screw and the surface at its end ?

And... seems to me there's something strange in the thread ... isn't it all 360° around the cylindric component ?

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[onelensman]

Seems likely a spacer shim is missing. Different thicknesses might originally be installed at factory to precisely calibrate each individual lens assembly to focus mount

[seneschal]

59 minutes ago, luigi bertolotti said:

Hmmm.. I saw your pictures after my previuos post... interesting... it makes me remember the coupling of the Telyt 280 lenshead to its focus unit (it too a "Canadian"  design) ... Isn't there an intermediate ring between the lenshead male screw and the surface at its end ?

And... seems to me there's something strange in the thread ... isn't it all 360° around the cylindric component ?

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Yes, I believe there should be a shim or some kind of spacer. It makes no sense to me that this would not be the sensible way to securely mount the lens head in the focusing mechanism.

I could do with someone who knows definitively how the adjustment and fixing of the lens is achieved.

... and yes, the place o have marked on the photo shows where there is around 2.5 - 3cm of residue in one of the threads. It is only in that short section and only in the single thread, no overlapping. I only discovered it today when I cleaned the thread. It does not go 360 degrees around the thread, only being max 3cm long and to me looks as if it were deliberately put there, it is too accurately applied for in not to be a deliberate act. It makes me wonder if Midland did not use a shim, but did, indeed use some thread locking material, once adjusted to ensure that the lens was screwed into the focusing mount the correct amount to achieve focus calibration.

Strange, but possible.

I could try it and find out if it works! Not a lot lost and if it does work then this lovely little lens will be better than when I received it... because the aperture ring will no longer be loose!

tempting🤣 

[seneschal]

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Oh, sorry, just quickly... it is the residue that does not go all the way round, just that small section on a single groove of the thread.

the thread itself goes all the way round, if you look closely at the low res photo, at the point you have arrowed as having no thread, you will see that the thread is continuous.

it is the reflection of the silver macbook that is causing the illusion of no thread.

[onelensman]

A possible solution if an engineering workshop is out of the question is to make a diy shim to fit the interface between lens block assembly and focus mount flange.

I have a Canon LTM body that uses multiple thin ring shape brass shims between the lens mounting flange and camera body to achieve precise lens to film plane registration. Using a similiar principle it may be possible to cut a series of rings from copper foil using a surgical scalpel to create a stack of shims that can be adjusted to the correct thickness required. Obviously this would require a good deal of improvisation, trial and error and also the skillset to solve mechanical repair issues which from your earlier post indicate you most certainly have.

[Michael Geschlecht]

Hello Seneschal,

Welcome to the Forum. It is good what you are doing.

You don't have to go to a person who makes things and "Re-Invent The Wheel". Just contact a person who repairs lenses like these. Tell them which lens + version, etc. And tell them the thickness of the spacer that you need. You might also ask for some tips if you need them.

You are doing quite well.

Best Regards,

Michael

[seneschal]

I tried to post an update on Saturday... but somehow lost the edit (after typing it on the iPhone!) that was quite a demoralising moment.

I know for certain now that Leica use a shim between the lens body and lens mount to achieve a secure mounting from the factory. Here's a post from a rangefinder forum where a guy unscrewed his Elmarit 28mm lens from the mount because the lens hood was not quite straight. He found a brass shim inside and assumed that not only was it causing his lens hood not to be straight but was also affecting his focus badly... WOW!

https://www.rangefinderforum.com/forums/archive/index.php/t-116303.html

We know from our investigations that the alignment of the hood is achieved by rotating the bezel, just three screws and an easy job. Not the best reason to unscrew the lens but proves the point about the shim.

@onelensman and @Michael Geschlecht you are absolutely right that I could and should get a new shim manufactured in brass by a precision engineer. I have used "reinforced" packing tape (which has evenly separated lines of nylon running through its length) to create a scale on the lens body which I can use to find the exact point at which the lens is in focus at the same time as the rangefinder. This is the correct position of the lens in the mount.

I can then measure the distance between the aperture ring and focus ring (two fixed points around the lens) using a micrometer. I then unscrew the lens until it just becomes loose from the mount thread and the distance between the two separations is the thickness of the necessary shim. I will do this and get a new shim machined to the correctly measure inside and outside diameter for the lens.

In the meantime, because I have a degree of impatience and because I want to use the lens while I wait, I have been investigating the use of thread lock in lenses.

It is common for thread lock to be used, ensuring that threads do not come loose due to usage or through vibration, in the old days a lacquer would be used to secure things like set screws. Nowadays we use thread lock.

We are probably all familiar with Loctite thread locks... but the question is which grade would be correct. There are about 5 common grades of Loctite and three readily available: purple, blue and red.

i) red is a strong bond and can only be separated by using heat, typically from a blowtorch

ii) blue is a medium hold, commonly found on auto parts such as brake calliper screws, and can be separated using norma tools

iii) purple is a weaker hold, and is suitable for metals such as brass or aluminium and for small screws up to 6mm in diameter, including grub or set screws

 

Purple is the correct grade and I have bought a small bottle of Loctite 222 purple which I will use both as an interim fix and as a securing agent when I get the shim made. The Loctite can be applied in the area that I wish to secure the threads, allowing adjustment to achieve perfect focus around that point, and then cures within the thread anaerobically over a period of 24 hours after which the bond can be broken without the use of excessive force. Ideal for the purpose.

So it looks like we have a resolution.

On the Elmarit 28mm version 3 we have discovered the following four fixes.

i) Realignment of the square lens hood when mounted is controlled by the position of the front bezel which is adjusted by loosening the three set screws which hold it securely in place.

ii) Realignment of the aperture ring index is achieved by opening or closing the diaphragm fully, loosening the three aperture ring set screws and rotating the ring until the index aligns with f2.8 or f22.

iii) An aperture ring which is loose to move up and down the barrel is secured by a split ring which mounts in a groove behind the aperture ring. The lens body has to be unscrewed from the focusing mount to re-fit this split ring.

iv) the focus calibration and secure mating of the lens body to the mount is achieved with a brass shim of specific thickness to that particular lens.

Thanks so much to everyone who contributed encouragement and ideas, it's amazing what we can achieve together. For those who have never dared to try this kind of thing, it shows that provided you take care and don't overreach then there is a lot you can discover about these beautiful "handcrafted" cameras that we all love and some small repairs you can certainly achieve yourself yourself.

For those who may have been trolled by others on this forum for daring to try something themselves... take heart. We definitely need the extraordinary skills that the experts who service our cameras provide. The high precision and complexity of many parts of a Leica camera don't lend themselves to being botched at home. BUT, certain things can be done with a modicum of technical skill, the correct good quality tools and an enquiring mind.

@pedaes, I was surprised by your attitude to my open hearted request for help. I am not sure what your "You took lens apart and created a problem. Go back over what you did. Most here would leave it to experts."

and your "Love your attitude. You have buggered it, end of." comments were supposed to achieve or how they would be helpful... just totally unnecessary.

I did not take the lens apart and create a problem, I took the lens apart, in order to diagnose an existing problem and fixed a loose aperture ring. I then discovered that there was another problem, I have diagnosed that and also fixed it. My attitude is one of exploration and childlike wonder, Keith Walker aka @pedaes. You, of all people, Keith should appreciate that interest in mechanical objects is not something to be mocked or that a childlike fascination and desire to dismantle things leads to greater knowledge and understanding, and can then be shared with others, which I have tried to do. How do you think your beloved steam engines are kept running? By engineers from Brunel's works in Swindon, England, or by gifted amateurs who are prepared to have a go and learn on the job?

Your comments @pedaes were not helpful, completely unnecessary and rather boring; like similarly framed photographs of similar subject matter, time after time, might be, even if each locomotive and the shape of the clouds of steam is marginally different. Just boring. I would suggest that we should all keep our vacuous comments to ourselves in fora like this one. The private communications that I have received from other members suggests that I am not the only one who finds trolling distasteful.

Onwards and upwards!

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[seneschal]

OK, temp fix made and surprisingly secure, aperture ring fixed, hood mounts perfectly square to the camera and I have got focus calibration as close as I can without using a proper focus chart. So I went out to take some shots quickly in the evening sun on with my 9 year old boy. I make my excuses for the poor framing and not spot on metering as I was attempting to concentrate on focusing!! I think they are reasonably close. All taken at full aperture to check focus rather than sharpness, all taken at ISO 160 on the M9 only the shutter speed is varying from around 1/30 up to about 1/250. All photos are jpegs straight out of the camera this morning and reduced in size to 1024x682. First time I have ever posted a photo taken with a camera, rather than an iPhone, on a forum.... scary!

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[seneschal]

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