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Zeiss Jenas and the migration of helicoid grease
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PostPosted: Mon Jan 16, 2023 6:13 pm    Post subject: Zeiss Jenas and the migration of helicoid grease Reply with quote
I exchanged a few messages with a technician who specializes in the repair of Zeiss lenses, and he mentioned that the Jena line of lenses are poorly sealed and that any kind of grease (stock or aftermarket) applied to the helicoid threads always escapes and moves into the optical chambers where it wreaks the usual havoc. The only solution he could offer was to apply a very thick grease that would not migrate, but it would make focusing a lot more difficult.

It got me thinking, are Jenas particularly prone to this problem over other lenses (i.e. weak seal), or are they all about the same? Are there any lenses known for a better seal that rarely have this issue?


PostPosted: Mon Jan 16, 2023 6:53 pm    Post subject: Reply with quote
I can tell you that mamiya zoom 70-150mm, which is a recent made one (80's?) suffer from the same issue, but it's very easy to remove the optics and clean it. Recently, I've had the nikkor 55mm 2.8 macro cla and they used a grease that makes focusing more stiff than fluid, excusing themselves as is the right one to avoid lens wobbling, but to be honest, I'm not happy with it, as critical focus is a pain. I do have plenty of lenses with no grease migration to elements, might be because they've got less usage or proper storage, who knows and still have fluid grease (zeiss c/y, septon, some early rokkors etc.).


PostPosted: Mon Jan 16, 2023 8:54 pm    Post subject: Reply with quote
Unfortunately focusing helicoids hold a fairly large amount of grease, even when the threads are only sparsely greased. Over time separation of the base oil is inevitable; with thicker greases it just takes longer.

Where that oil will end up is very much dependent on the lens design, and materials used.

Lenses are rarely sealed against oil ingress, as far as I am aware. That would involve hermetically sealing and bonding the lenses into the mount. The best preventative measures I have seen used in lenses are oil diffusion barriers, either in the form of an oleophobic fluorocarbon barrier coating on the mount near the helicoid, or a machined discontinuity in a relevant capillary gap.


PostPosted: Tue Jan 17, 2023 6:33 am    Post subject: Reply with quote
kiddo wrote:
I'm not happy with it, as critical focus is a pain.


Yeah, I'm not excited about slow helicoids. He said that if I really wanted, he could use some lighter grease but that it might be all over my blades within a matter of months. So now I'm just thinking that I need to spend more money on lenses that are verified to be without issues. But with more money on the table, the question becomes whether these old Jenas are a good investment to begin with.

You can see how I ended up here.


PostPosted: Tue Jan 17, 2023 6:36 am    Post subject: Reply with quote
RokkorDoctor wrote:
Where that oil will end up is very much dependent on the lens design, and materials used.


Are more premium brass lenses less susceptible to traveling grease/oil, or is it the same story with cheaper aluminum lenses?


PostPosted: Tue Jan 17, 2023 7:36 am    Post subject: Reply with quote
kiddo wrote:
I can tell you that mamiya zoom 70-150mm, which is a recent made one (80's?) suffer from the same issue, but it's very easy to remove the optics and clean it. Recently, I've had the nikkor 55mm 2.8 macro cla and they used a grease that makes focusing more stiff than fluid, excusing themselves as is the right one to avoid lens wobbling, but to be honest, I'm not happy with it, as critical focus is a pain. I do have plenty of lenses with no grease migration to elements, might be because they've got less usage or proper storage, who knows and still have fluid grease (zeiss c/y, septon, some early rokkors etc.).


The Nikkor 55/2.8 usually suffers from this. It's also double helicoid and thus a pain to service.


PostPosted: Tue Jan 17, 2023 11:10 am    Post subject: Reply with quote
QuickHitRecord wrote:
RokkorDoctor wrote:
Where that oil will end up is very much dependent on the lens design, and materials used.


Are more premium brass lenses less susceptible to traveling grease/oil, or is it the same story with cheaper aluminum lenses?


I have seen the problem in both; it really depends on how much of an oxide layer has built up on the brass and whether or not the aluminium part has been anodised.

I also think there is a misconception re. brass being a premium material vs. cheap aluminium. Brass is more expensive per unit volume yes, but in a lens the material cost of brass vs aluminium is neither here nor there; the difference in the material cost of brass vs. aluminium pales in comparison to the machining cost for the relevant parts of the lens mount / barrel / helicoid.

The dominant reason makers moved away from brass is not one of cost, but rather the really massive reduction in weight when using aluminium instead. Once you start servicing lenses and notice how much of the weight of a "classic" lens is made up by the brass helicoid, this becomes obvious...

There is also a (partial) myth re. the smoother focussing of brass helicoids. When properly lubricated with an appropriate fresh grease, there is no noticeable difference in focusing feel between brass or aluminium helicoids. The difference becomes noticeable when the base oil separates out and the grease can no longer prevent dry direct surface contact between the two helicoid parts. At that point a brass helicoid definitely feels smoother than an aluminium helicoid, but really by that stage the grease has failed and is no longer serviceable, and the lens is way overdue a clean & re-lube.

This problem was partly addressed by many lens manufacturers from ca. the mid/late-60's onwards by adding a dry-lube additive to the grease, such as molybdenum disulfide. Molybdenum disulfide powder is dark grey in appearance not unlike graphite but adheres better to metals and aluminium in particular, and is easily recognisable if you get some on your best light coloured clothing or sofa; it will never come out... Sad


PostPosted: Tue Jan 17, 2023 1:05 pm    Post subject: Reply with quote
My CZJ lenses all are a bit stiff focussing to one degree or another. The Cheap Tessars are worst (I have three, only one is OK). Unlike my Takumars, (I have dozens) only a few of them suffer from focussing problems. Most are butter smoothy but with a pleasant resistance. Yashica usually performs well, Mamiya-Sekor on the other hand is stiffening up a lot over time.


PostPosted: Tue Jan 17, 2023 2:14 pm    Post subject: Reply with quote
Yeah, Zeiss Jena lenses all seem to show similar problems with the focusing, which makes sense considering they probably used the same type of grease and the lenses are of a relatively similar age now. In my case some are pretty stiff (but usable), some all right but those show early signs of the problem (not a very smooth feeling, a bit "scratchy", but still with decent, equal resistance).
I usually use my M42 lenses with the focusing helicoid anyway, so I focus some lenses this way instead; as I delay dealing with them (I still need to choose a decent grease, and more you think and know about the issues, less you know what to do...).
Japanese lenses are generally better in this regard (though not always perfect). So far my best experience is with Minolta, all the lenses I have are almost good as new (kinda perfect resistance, I just never used a new one so I can't say how much the grease decayed).


PostPosted: Tue Jan 17, 2023 5:06 pm    Post subject: Reply with quote
I find that as a general rule the grease used in German lenses gets stiff faster than similar era Japanese lenses. CZJ are among the worst for this, but Enna, Meyer and Piesker are not much better. Schact and Schneider are a little bit better. Especially the Schneider Retina lenses. Takumar are absolutely the the best. I say this having purchased well over a thousand vintage lenses.


PostPosted: Tue Jan 17, 2023 6:55 pm    Post subject: Reply with quote
jamaeolus wrote:
I find that as a general rule the grease used in German lenses gets stiff faster than similar era Japanese lenses. CZJ are among the worst for this, but Enna, Meyer and Piesker are not much better. Schact and Schneider are a little bit better. Especially the Schneider Retina lenses. Takumar are absolutely the the best. I say this having purchased well over a thousand vintage lenses.


There is a good chance that the grease in those older German lenses had a mix of organic base oils rather than a purer synthetic base oil. The more volatile of those base oil constituents evaporates relatively quickly which makes the grease stiffen up faster. A good giveaway is if those greases (at least when new) had a relatively strong odour.


PostPosted: Tue Jan 17, 2023 9:06 pm    Post subject: Reply with quote
jamaeolus wrote:
I find that as a general rule the grease used in German lenses gets stiff faster than similar era Japanese lenses. CZJ are among the worst for this, but Enna, Meyer and Piesker are not much better. Schact and Schneider are a little bit better. Especially the Schneider Retina lenses. Takumar are absolutely the the best. I say this having purchased well over a thousand vintage lenses.


I’ve very good experiences with Takumars as well in this regard. Never encountered a stiff Takumar I believe. Minolta also good. Among the Japanese lenses, I’ve seen many stiff Nikkors; the pre-ai’s generally better in my experience. I only have little experience with German lenses. My CZJ Sonnar 135/3.5 operates very smoothly, probably it had service and new grease.


PostPosted: Tue Jan 17, 2023 9:19 pm    Post subject: Reply with quote
RokkorDoctor wrote:

There is also a (partial) myth re. the smoother focussing of brass helicoids. When properly lubricated with an appropriate fresh grease, there is no noticeable difference in focusing feel between brass or aluminium helicoids. The difference becomes noticeable when the base oil separates out and the grease can no longer prevent dry direct surface contact between the two helicoid parts. At that point a brass helicoid definitely feels smoother than an aluminium helicoid, but really by that stage the grease has failed and is no longer serviceable, and the lens is way overdue a clean & re-lube.


No.

I have quite a few Minolta MD-III lenses (alu-on-alu), and even more MC-II/MC-X lenses (usually brass-on-alu). And I've had several of those MD-III lenses re-lubricated by the former head of servicing at Minolta Switzerland (with the proper greases recommended by Minolta). None of the re-lubricated / serviced MD-III lenses did focus as smoothly as the correponding MC-II/MC-X lenses ... in fact they didn't improve much at all (after re-lubrication)!

S


PostPosted: Wed Jan 18, 2023 2:43 am    Post subject: Reply with quote
Early mc rokkor are the best , but septon is just the same, Zeiss c/y almost as nice to focus , I don't own takumars. A 30-40's trioplan from a folding camera is also smooth to focus,clean aperture and no grease migration, and that's very weird ,as the body it's got plenty of use , dust was easy to remove , but no fungus at all neither coatings affected in such an old lens (nice surprise)


PostPosted: Wed Jan 18, 2023 4:08 am    Post subject: Reply with quote
I have only had maybe 15-20 Jena lenses all told, and only one of them was noticeably tight, a triotar 135mm. The rest seemed no better or worse than any other lens from that period. I've had Japanese lenses from the same period or even later with frozen solid helicoids, but not so often from the same manufacturer that it stood out. I disassembled a Nikon 20cm F/4 last week with the aluminium on aluminium helicoid completely stuck, normally the only fault I can find on Nikon lenses is slight over-looseness, probably from lots of use. I've tried lots of lenses from a vast number or makers, but the only times I genuinely think it's a manufacturing issue is on those where a reputation precedes the item, like on the Pax camera helicoids or the large Soviet lenses like the older model Helios 40 lenses. The rest of the time I assume it's due to the places that piece of photographic equipment has been in its 50+year lifetime. With the amount of information sharing afforded by modern technology, IMO, if the Jena lenses were much worse than their contemporaries, it would already be well known.


PostPosted: Wed Jan 18, 2023 10:54 am    Post subject: Reply with quote
An important part of lens manual should be input on how to store lens. Usually grease can only reach aperture system at specific orientation. Generally rear side up is better. This goes for practically all lenses not just Jena.


PostPosted: Wed Jan 18, 2023 12:54 pm    Post subject: Reply with quote
stevemark wrote:
RokkorDoctor wrote:

There is also a (partial) myth re. the smoother focussing of brass helicoids. When properly lubricated with an appropriate fresh grease, there is no noticeable difference in focusing feel between brass or aluminium helicoids. The difference becomes noticeable when the base oil separates out and the grease can no longer prevent dry direct surface contact between the two helicoid parts. At that point a brass helicoid definitely feels smoother than an aluminium helicoid, but really by that stage the grease has failed and is no longer serviceable, and the lens is way overdue a clean & re-lube.


No.

I have quite a few Minolta MD-III lenses (alu-on-alu), and even more MC-II/MC-X lenses (usually brass-on-alu). And I've had several of those MD-III lenses re-lubricated by the former head of servicing at Minolta Switzerland (with the proper greases recommended by Minolta). None of the re-lubricated / serviced MD-III lenses did focus as smoothly as the correponding MC-II/MC-X lenses ... in fact they didn't improve much at all (after re-lubrication)!

S


Maybe our experience differs here Stephan; I have 150+ Rokkor lenses with brass/alu helicoids and 100+ MDIII lenses with alu/alu helicoids. I feel no difference in focusing re. MC vs MDIII on 100+ of those I have re-lubed myself, except where the helicoid geometry of certain specific lenses would cause a predictable difference.

I can't comment on the servicing you had done on your MDIII lenses by Minolta's former head of servicing, apart from that if that was done relatively recently (last 20 years or so), the original Losimol greases Minolta originally used in their Rokkor lenses would no longer have been available, unless he still had old stock left himself.

I service my own lenses, and my own experience with the failing helicoid lubrication on MC lenses vs MD(III) lenses is as follows:

About half the MC lenses still had a normal focus feel when I got them, and on inspection the helicoids of those still had a serviceable amount of base oil left in the grease (I still cleaned and re-lubed them on account of visible aging of the grease and build-up of contamination).

The other half of the MC lenses all felt super nice smooth & light focusing when I got them, but had a minute slop in the focusing helicoid (less than 50 microns probably but noticeable nevertheless if one goes looking for it.) Upon inspecting the helicoids of those I found that on all of them virtually all, if not all, the base oil had gone and the helicoid was simply sliding super smoothly on a dry bed of residual soap thickener & molybdenum disulfide (later MC), or dried-up soap thickener alone (earlier MC, likely lithium stearate, but not sure). They sure felt super nice focusing, but from an optical engineering perspective the lubricant had failed and had lost its mechanical stabilisation properties where the lubricant no longer effectively takes up the necessary machined gap tolerance between the two helicoid threads, resulting in minute slop and focus hysteresis at f/2 or wider apertures.

Smoother focusing when using a brass component in the the helicoid simply makes no sense from an engineering perspective, once properly lubricated. If there is a difference, you are looking at a difference in machining tolerances, rather than a difference in materials. The surface molecules of the brass part simply are unaware of the type of surface molecules of the other helicoid part sitting on the other side of the grease/oil film. For sure, there is a huge difference in the sliding properties of alu-on-alu vs alu-on-brass, but that is when dry, without any lubrication, where the use of brass then virtually eliminates the possibility of fretting/galling.

Ultimately in a properly lubricated helicoid the entire surface of the thread should be covered in a very thin film of lubricant (if anything to prevent oxidisation of the thread surfaces). This film will mitigate any direct dry surface contact between the two helicoid threads, and the feel of focus then becomes entirely determined by the rheological shear properties of the grease as well its adhesion properties to the alu or brass substrate. Assuming equal machining tolerances, the feel of alu/alu, alu/plastic, alu/brass or brass/brass helicoids should be similar once lubricated; if not that indicates either different machining tolerances or dry thread surface contact, the latter an indication of a failing/failed/inappropriate lubricant.

It should be noted that the feel of focus is often determined by the fine thread of the double helicoid rather than the course thread. Nearly all lenses have double helicoid focusing; one course one which does the focusing, and a fine one by which the focus grip part screws into the base of the lens. Many macro lenses have a two course thread double helicoid to facilitate the longer required extension within a full turn of the focus grip, easily recognised by the focus grip itself moving forward quite a bit when focusing in. When re-lubricating special attention needs to be given to very thoroughly cleaning the fine helicoid threads, as even the smallest amount of contamination in there affects the focus feel, much more so than in the course threads.


PostPosted: Wed Jan 18, 2023 1:01 pm    Post subject: Reply with quote
Pancolart wrote:
An important part of lens manual should be input on how to store lens. Usually grease can only reach aperture system at specific orientation. Generally rear side up is better. This goes for practically all lenses not just Jena.


That is a valid observation, and it will help for sure, but in many lenses the diffusion/creep/migration of the released oil by virtue of the high surface energy of metals and also capillary forces can easily overcome the gravitational pull on the oil. Oil films flow down many plastics & glass, but creep up most metals...


PostPosted: Wed Jan 18, 2023 8:17 pm    Post subject: Reply with quote
In 32 years in my job as a maintaince engineer in the sewage treatment industry we used a lot of different greases, and had 220kg drums lined up at the back of the workshop. The molybdenum disulfide grease ALWAYS had a puddle of oil that was leaching out of the grease, none of the other grease barrels had any leaching.

Where we used the molybdenum disulfide grease was mainly on high pressure screw shafts on valves and penstocks, some of which had gates that were over a ton in weight and moved by 4 inch square threads, mostly stainless steel in a brass nut. Most of these valves were used regularly with automatic motors. The grease worked perfectly in this situation and even exposed to the weather the lube was never an issue, and we saw no sign of leaching. In a situation where the valve or machine was very rarely used we would see the oil leach out and leave the grease residue to get harder and thicker. In a low torque / small shaft situation the grease could even stop the rotation.

Molybdenum disulfide grease seems to be OK in a situation where it is 'used' frequently, and kept 'mixed', and for that reason I don't use it in any lens. A few years ago I put about a teaspoon of molybdenum disulfide grease, well mixed from the barrel, in a small container and left it sitting in the house. In less tham a month there was leaching.


PostPosted: Wed Jan 18, 2023 9:29 pm    Post subject: Reply with quote
caspert79 wrote:
jamaeolus wrote:
I find that as a general rule the grease used in German lenses gets stiff faster than similar era Japanese lenses. CZJ are among the worst for this, but Enna, Meyer and Piesker are not much better. Schact and Schneider are a little bit better. Especially the Schneider Retina lenses. Takumar are absolutely the the best. I say this having purchased well over a thousand vintage lenses.


I’ve very good experiences with Takumars as well in this regard. Never encountered a stiff Takumar I believe. Minolta also good. Among the Japanese lenses, I’ve seen many stiff Nikkors; the pre-ai’s generally better in my experience. I only have little experience with German lenses. My CZJ Sonnar 135/3.5 operates very smoothly, probably it had service and new grease.


Only two of my Takumar 1:3.5 f-135 (Model I, produced 1957-1961) have stiff helicoids. All the others, maybe an hundred or so, are "buttery" smooth.

GDR Pentacon 2.8 / 135 and CZJ Flektogon 2.8 / 35 are both very stiff.


PostPosted: Wed Jan 18, 2023 10:03 pm    Post subject: Reply with quote
RokkorDoctor wrote:

Maybe our experience differs here Stephan; I have 150+ Rokkor lenses with brass/alu helicoids and 100+ MDIII lenses with alu/alu helicoids. I feel no difference in focusing re. MC vs MDIII on 100+ of those I have re-lubed myself, except where the helicoid geometry of certain specific lenses would cause a predictable difference.

I can't comment on the servicing you had done on your MDIII lenses by Minolta's former head of servicing, apart from that if that was done relatively recently (last 20 years or so), the original Losimol greases Minolta originally used in their Rokkor lenses would no longer have been available, unless he still had old stock left himself.

I service my own lenses, and my own experience with the failing helicoid lubrication on MC lenses vs MD(III) lenses is as follows:

About half the MC lenses still had a normal focus feel when I got them, and on inspection the helicoids of those still had a serviceable amount of base oil left in the grease (I still cleaned and re-lubed them on account of visible aging of the grease and build-up of contamination).

The other half of the MC lenses all felt super nice smooth & light focusing when I got them, but had a minute slop in the focusing helicoid (less than 50 microns probably but noticeable nevertheless if one goes looking for it.) Upon inspecting the helicoids of those I found that on all of them virtually all, if not all, the base oil had gone and the helicoid was simply sliding super smoothly on a dry bed of residual soap thickener & molybdenum disulfide (later MC), or dried-up soap thickener alone (earlier MC, likely lithium stearate, but not sure). They sure felt super nice focusing, but from an optical engineering perspective the lubricant had failed and had lost its mechanical stabilisation properties where the lubricant no longer effectively takes up the necessary machined gap tolerance between the two helicoid threads, resulting in minute slop and focus hysteresis at f/2 or wider apertures.

Smoother focusing when using a brass component in the the helicoid simply makes no sense from an engineering perspective, once properly lubricated. If there is a difference, you are looking at a difference in machining tolerances, rather than a difference in materials. The surface molecules of the brass part simply are unaware of the type of surface molecules of the other helicoid part sitting on the other side of the grease/oil film. For sure, there is a huge difference in the sliding properties of alu-on-alu vs alu-on-brass, but that is when dry, without any lubrication, where the use of brass then virtually eliminates the possibility of fretting/galling.

Ultimately in a properly lubricated helicoid the entire surface of the thread should be covered in a very thin film of lubricant (if anything to prevent oxidisation of the thread surfaces). This film will mitigate any direct dry surface contact between the two helicoid threads, and the feel of focus then becomes entirely determined by the rheological shear properties of the grease as well its adhesion properties to the alu or brass substrate. Assuming equal machining tolerances, the feel of alu/alu, alu/plastic, alu/brass or brass/brass helicoids should be similar once lubricated; if not that indicates either different machining tolerances or dry thread surface contact, the latter an indication of a failing/failed/inappropriate lubricant.

It should be noted that the feel of focus is often determined by the fine thread of the double helicoid rather than the course thread. Nearly all lenses have double helicoid focusing; one course one which does the focusing, and a fine one by which the focus grip part screws into the base of the lens. Many macro lenses have a two course thread double helicoid to facilitate the longer required extension within a full turn of the focus grip, easily recognised by the focus grip itself moving forward quite a bit when focusing in. When re-lubricating special attention needs to be given to very thoroughly cleaning the fine helicoid threads, as even the smallest amount of contamination in there affects the focus feel, much more so than in the course threads.


Thanks, Mark, very interesting.


PostPosted: Thu Jan 19, 2023 10:52 am    Post subject: Reply with quote
Lloydy wrote:
In 32 years in my job as a maintaince engineer in the sewage treatment industry we used a lot of different greases, and had 220kg drums lined up at the back of the workshop. The molybdenum disulfide grease ALWAYS had a puddle of oil that was leaching out of the grease, none of the other grease barrels had any leaching.

Where we used the molybdenum disulfide grease was mainly on high pressure screw shafts on valves and penstocks, some of which had gates that were over a ton in weight and moved by 4 inch square threads, mostly stainless steel in a brass nut. Most of these valves were used regularly with automatic motors. The grease worked perfectly in this situation and even exposed to the weather the lube was never an issue, and we saw no sign of leaching. In a situation where the valve or machine was very rarely used we would see the oil leach out and leave the grease residue to get harder and thicker. In a low torque / small shaft situation the grease could even stop the rotation.

Molybdenum disulfide grease seems to be OK in a situation where it is 'used' frequently, and kept 'mixed', and for that reason I don't use it in any lens. A few years ago I put about a teaspoon of molybdenum disulfide grease, well mixed from the barrel, in a small container and left it sitting in the house. In less tham a month there was leaching.


One of many good reasons why you don't see molybdenum disulfide used anymore in lens helicoids these days... Wink

Interestingly I have come across quite a bit of anecdotal evidence that greases with a molybdenum disulfide additive are more prone to oil seepage; you are far from the first engineer to suggest that...

Truth be told, molybdenum disulfide always was a bit of overkill to be used in lenses as a helicoid grease dry lube additive, as its primary function is to provide last-resort dry lubrication in the event of grease failure where there is a very high surface contact pressure. Those high surface contact pressures never really occur in lens helicoids, unless the helicoid has been severely deformed.

I guess lens manufacturers added it as a dry lubricant choice over graphite because of its stable chemical properties and better adherence to metals; and based on its use in the automotive industry it may even simply have been a "fashionable" choice of dry-lube additive amongst engineers in general at the time.

Molybdenum disulfide (together with graphite) still has a use in lens servicing though, but primarily as a sparingly applied pure dry lubricant used on e.g. aperture actuation levers in the mount, or even the moving ring holding the aperture blades (but not on the blades themselves)

Nowadays micronised PTFE (teflon) is often used as a dry lubricant additive for helicoid grease, which is a lot less messy...


PostPosted: Thu Jan 19, 2023 11:33 am    Post subject: Reply with quote
The tendancy to 'overkill' is very common, there have been many topics on every photo forum for ever about lube for helicoids, and there is always someone telling everyone that they must use a particular EP grease - of one sort or another. EP is Extreme Pressure grease designed for loads measured in tons and high temp's found in truck wheel bearings! WHY??

For the loads and probable heat range a lens is likely to see all that's needed is a good quality General Purpose grease - if a lens is subjected to greater loads than a bicycle headstock then grease isn't going to save it!

The type of grease is another discussion entirely, but the grade needs to be the lightest possible without sloughing or leaching.
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