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Archive 2023 · Zeiss ZM Wobble - 2023 Edition..

  
 
bluehawaii
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p.1 #1 · p.1 #1 · Zeiss ZM Wobble - 2023 Edition..


Hi everyone,

Optimistically I sent a lens back to Zeiss with the "Zeiss ZM Wobble" focus wobble/play. After some months they proudly returned it to me without any improvement after it had a made the trip to a third party repairer workshop under their control.

So I sent it back in again to Zeiss, who forwarded it onwards to Germany. Although this time to the head office.

Next system of events was to send me another brand new lens from Germany that has exactly the same amount of wobbleiness (if that is the right word). I sent this one straight back in.

Recently Zeiss have written an official letter for me now saying the backlash is normal. I am somewhat surprised by all this since the website proudly explains how smooth the focus is and without play I have found a specialist company who can correct the issue but it isn’t a cheap job. I have several other of their lenses and they are all fine, seems to be just some lenses that have it. I have asked a few questions suggesting some amendments to the website adverts and am waiting for an answer.

Did anyone find a good solution in the end?

I found another thread on this forum explaining a similar wobble focus play with the ZM lenses. This is the thread I am referring to: ZM Wobble.

Thanks.



Mar 16, 2023 at 06:49 PM
thrice
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p.1 #2 · p.1 #2 · Zeiss ZM Wobble - 2023 Edition..


Which lens do you have which supposedly has a normal wobble? So I can avoid that model like the plague going forward.


Mar 17, 2023 at 03:50 AM
bluehawaii
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p.1 #3 · p.1 #3 · Zeiss ZM Wobble - 2023 Edition..


Hi, it is the ZEISS C Biogon T* 2.8/35 ZM aka. 35mm Compact Biogon.


Mar 17, 2023 at 04:31 AM
panos.v
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p.1 #4 · p.1 #4 · Zeiss ZM Wobble - 2023 Edition..


Good to see Zeiss is keeping up with Leica when it comes to servicing.


Mar 17, 2023 at 04:55 AM
thrice
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p.1 #5 · p.1 #5 · Zeiss ZM Wobble - 2023 Edition..


My silver C biogon I bought back in 2010 had no perceptible wobble or backlash.

I sold the lens around 2012 though. Cracker of a lens!

bluehawaii wrote:
Hi, it is the ZEISS C Biogon T* 2.8/35 ZM aka. 35mm Compact Biogon.




Mar 17, 2023 at 06:11 AM
hmzimelka
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p.1 #6 · p.1 #6 · Zeiss ZM Wobble - 2023 Edition..


What type of wobble are you experiencing because there is focus backlash and then there is the Zeiss Wobble, and the two are not really the same.

The proverbial Zeiss wobble has the front optical assembly, the portion in front of the focus ring, that has rotational and general play.

What Zeiss tends to do with their recent production lenses is strive for an ultimately light focus feel. This means light grease, and internal guides and tabs that are not tight fitting in order to avoid additional friction. Both the Distagon 50/2 I have and the Biogon-C 35mm I had had a slight looseness in the focus ring which would become very obvious when rotating the focus ring gently back and forth. The brass tab responsible for driving the focus ring forces to the internal helicoid, is the part that can wear with time and is fairly loosely fitting to begin with.

I absolutely hated this looseness, and I fixed it by removing the tab and hammering it a little fatter. It takes very little effort, and it needs to be done with great care to not over do it. It's also important to use flat surfaces and every effort to keep both sides flat.

After this, the looseness was gone. Another less invasive trick is to apply a thicker grease in this gap where the tab runs up and down. It can take some of the backlash away when changing the focus direction but it's not a suitable fix.

Voigtlander implements this better in having a tuning fork design tab that can be bent wider when it wears down. It's therefore a far easier fix with most voigtlander lenses.

What I noticed with some Zeiss lenses is that the helicoids may need very light grease and sometimes quite a bit of it to remove a binding action that takes place when focusing the lens in vertical orientation rather than the normal horizontal. It really depends just how loosely the helicoids were lapped at the factory.

It was really a trial and error getting my Planar up to snuff, or better said, to my liking.




Mar 17, 2023 at 11:45 AM
bluehawaii
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p.1 #7 · p.1 #7 · Zeiss ZM Wobble - 2023 Edition..


panos.v wrote:
Good to see Zeiss is keeping up with Leica when it comes to servicing.


A progression down market. I hope both Cosina & Leica can get things back on track because I always had a good impression of them in the past.

---------------------------------------------

thrice wrote:
My silver C biogon I bought back in 2010 had no perceptible wobble or backlash.

I sold the lens around 2012 though. Cracker of a lens!



Thanks for sharing. Good to know you can have a set of them that all perform just as advertised.

I have never once owned a lens like this before.

A cheap Jupiter 8, Chinese Artisan etc. etc. or pretty much any other lens made in the past 100 years feels fine. Then switch over to the ZM 50 or 28 and they're ok too. Put on the wobbly 35mm and you just feel the clicking/wobble feeling. It's bad.





Mar 17, 2023 at 11:59 AM
bluehawaii
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p.1 #8 · p.1 #8 · Zeiss ZM Wobble - 2023 Edition..


hmzimelka wrote:
...It was really a trial and error getting my Planar up to snuff, or better said, to my liking.



That's very interesting. I think looseness as you said is the best way to describe it. The front part of the lens where the lens hood mounts is ok. The lens mount to the camera itself is ok. For example if I use a Cosina Nokton 35mm and rock focus back and forth there is no rotational play at all and even less friction it just feels perfect like a Leica lens, whereas on the C. Biogon 35mm there is some free travel where no focusing is happening and then a slight click, very off putting since with a rangefinder you often just work the focus back and fourth slightly. Like you I hate it but unlike you unfortunately would never dream of opening this new lens up and trying to repair it. Well done for fixing yours! I think it's very interesting that some are fine and others have play in these focusing guides or tabs as you have explained. I read that there is a Teflon roller system somewhere that needs adjusting as well, not sure which lens has that or whether it's some other brand/model.




Mar 17, 2023 at 12:20 PM
hmzimelka
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p.1 #9 · p.1 #9 · Zeiss ZM Wobble - 2023 Edition..


bluehawaii wrote:
That's very interesting. I think looseness as you said is the best way to describe it. The front part of the lens where the lens hood mounts is ok. The lens mount to the camera itself is ok. For example if I use a Cosina Nokton 35mm and rock focus back and forth there is no rotational play at all and even less friction it just feels perfect like a Leica lens, whereas on the C. Biogon 35mm there is some free travel where no focusing is happening and then a slight click, very off putting since with a rangefinder
...Show more

WIth the possible exception of the ZM 35mm f/1.4 (haven't used or opened one), then there are NO teflon rollers or guides or anything teflon in ZM lenses. I saw something teflon in my ZF Distagon 35/2 but I've not managed to get deeper into that lens. The VM lenses are simple, just like Voigtlander lenses. Except I think Voigtlander are better at their internal design language.

The classical Zeiss ZM wobble I suspect is like the wobble one can get on Voigtlander and some Leica alike that have a retaining ring holding the optical block together with the focusing unit. This ring needs to loosen slightly, and then the wobble occurs. Zeiss have resorted to using thread lock, and sometimes strong thread lock, which makes servicing the lenses a bit sketchy... one needs to be very very patient and apply one or two tiny drops of acetone into the right place for capillary action to draw the liquid into the threads and soften the thread lock. Voigtlander does the same; My Color-Skopar 35/2.5 was impossibly difficult to get off.

The problem with Ziess' mechanism that is causing this focusing play, is that the copper tab is soft, and it rides on either a hardened aluminium or steel ring. The copper wears down, and often doesn't take all that long. We're talking 0.02mm wear is enough to cause play one can feel when fine tuning focus. On my Planar, the focus ring drives the focusing mechanism with a single little tab, whereas Voigtlander usually have two tabs 180º apart. This spreads the load and it also reduces binding when the lens is at a funny angle.




Mar 17, 2023 at 02:40 PM
bluehawaii
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p.1 #10 · p.1 #10 · Zeiss ZM Wobble - 2023 Edition..


hmzimelka wrote:
WIth the possible exception of the ZM 35mm f/1.4 (haven't used or opened one), then there are NO teflon rollers or guides or anything teflon in ZM lenses. I saw something teflon in my ZF Distagon 35/2 but I've not managed to get deeper into that lens. The VM lenses are simple, just like Voigtlander lenses. Except I think Voigtlander are better at their internal design language.

The classical Zeiss ZM wobble I suspect is like the wobble one can get on Voigtlander and some Leica alike that have a retaining ring holding the optical block together with the focusing unit.
...Show more

Interesting, so no Teflon rollers.

Just this small brass or alloy part out of spec on some new lenses and can wear down and get worse. And then a locking ring system that sometimes comes loose on older lenses.

Correct me if i'm wrong but it sounds like there was an early batch with focus problems. Then a good batch for a quite a while (perhaps around 2010 onwards). Someone a while back commented on a post that it was a 2003 problem that never happens now.

Looking back through forum posts. Some are sold listings, often the seller cares to point out that focus is 100% perfect. Some other general forum posts where folks have just returned lenses (upto 3 times) and therefore ended up with a good one eventually.

How many times that happened over the years we just don't know. I guess you can be sure someone at Carl Zeiss knows that.

I wonder where the returned lenses end up. I assume back at Zeiss. So instead of making the parts you mentioned fit nicely it seems they could be sending them back out? I really hope this isn’t what’s happening.

I asked to speak to the manager. They have emailed and said someone from Germany tried to call but as yet nothing heard.






Mar 18, 2023 at 07:03 AM
hmzimelka
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p.1 #11 · p.1 #11 · Zeiss ZM Wobble - 2023 Edition..


The brass focus tab is in spec. Zeiss' specification for this light focus feel is very deliberate, and every friction piece in the lens needs to compliment this design choice; If the tab is too tight, it will ad resistance to focus. Every Zeiss ZM lens I own, owned or used, were all very light in focus. While I've only only used a handful of Zeiss lenses, I don't quite like this choice for super light focus feel.

I don't know about focus problem with ZM lenses. Only about the rangefinder calibration preferences for the 50mm Sonnar lens, which was either optimised for f/2, f/2.8 or wide open at f/1.5 throughout its lifetime.



Mar 18, 2023 at 07:30 AM
bluehawaii
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p.1 #12 · p.1 #12 · Zeiss ZM Wobble - 2023 Edition..


hmzimelka wrote:
The brass focus tab is in spec. Zeiss' specification for this light focus feel is very deliberate, and every friction piece in the lens needs to compliment this design choice; If the tab is too tight, it will ad resistance to focus. Every Zeiss ZM lens I own, owned or used, were all very light in focus. While I've only only used a handful of Zeiss lenses, I don't quite like this choice for super light focus feel.

I don't know about focus problem with ZM lenses. Only about the rangefinder calibration preferences for the 50mm Sonnar lens, which was
...Show more



I can see exactly what you mean now.

In the picture at the very bottom of this page, on the bottom right of the picture – is that the part you are referring to.

https://yukosteel.wordpress.com/2018/07/02/disassembly-carl-zeiss-c-sonnar-t-50mm-f1-5-zm-lens/

The copper/brass coloured part just inside the focusing tab on the focus ring – held in with the 2 screws?

And if you buy a new sonnar it comes as a 2.8 optimised and needs the extra shim to optimise it at 1.5. Never knew that!


Here you can see the whole thing stripped out and all the parts.

https://yukosteel.wordpress.com/2021/06/06/disassembly-carl-zeiss-biogon-t-35mm-f2-zm-lens/

It does look like a normal type of lens, I am just wondering what this guy meant when he said there were Teflon rollers. Just as you say there is nothing there in that lens.


I searched high and low and found this on flickr regarding a Samyang 85mm Teflon roller lens…

https://www.flickr.com/photos/gigel/albums/72157626746203425



Mar 18, 2023 at 01:21 PM
hmzimelka
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p.1 #13 · p.1 #13 · Zeiss ZM Wobble - 2023 Edition..


I can see exactly what you mean now.

In the picture at the very bottom of this page, on the bottom right of the picture – is that the part you are referring to.

https://yukosteel.wordpress.com/2018/07/02/disassembly-carl-zeiss-c-sonnar-t-50mm-f1-5-zm-lens/

The copper/brass coloured part just inside the focusing tab on the focus ring – held in with the 2 screws?


Yes exactly.

And if you buy a new sonnar it comes as a 2.8 optimised and needs the extra shim to optimise it at 1.5. Never knew that!

Here you can see the whole thing stripped out and all the parts.

https://yukosteel.wordpress.com/2021/06/06/disassembly-carl-zeiss-biogon-t-35mm-f2-zm-lens/

It does look like a normal type of lens, I am just wondering what this guy meant when he said there were Teflon rollers. Just as you say there is nothing there in that lens.

I searched high and low and found this on flickr regarding a Samyang 85mm Teflon roller lens…

https://www.flickr.com/photos/gigel/albums/72157626746203425


You ad a shim to correct a back focus. So buying a lens that is optimised for f/2.8 is ideal since one can remove one of the thinner shims to have the lens focus better for a wider aperture like f/2. It depends on how many shims are in the stack, and the thickness of each shim.

Focus shift from stopping a lens down moves the focus away and causes a back focus. Adding a shim will correct for this at a specific aperture, but then at wider apertures you'll have a front focus.



Mar 20, 2023 at 12:34 AM
thrice
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p.1 #14 · p.1 #14 · Zeiss ZM Wobble - 2023 Edition..


My 35/1.4 ZM distagon is very difficult to focus compared to all Leica/Voigtlander lenses I own or have owned. It is also inconsistent indicating the lubricant is either not even or the helicoid is improperly machined but I would say more likely the former.

hmzimelka wrote:
The brass focus tab is in spec. Zeiss' specification for this light focus feel is very deliberate, and every friction piece in the lens needs to compliment this design choice; If the tab is too tight, it will ad resistance to focus. Every Zeiss ZM lens I own, owned or used, were all very light in focus. While I've only only used a handful of Zeiss lenses, I don't quite like this choice for super light focus feel.

I don't know about focus problem with ZM lenses. Only about the rangefinder calibration preferences for the 50mm Sonnar lens, which was
...Show more



Mar 20, 2023 at 03:56 PM
modlin
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p.1 #15 · p.1 #15 · Zeiss ZM Wobble - 2023 Edition..


panos.v wrote:
Good to see Zeiss is keeping up with Leica when it comes to servicing.


Its not about the servicing...its about the ' "experience" with a German brand '

ps.This explanation stuck in my mind when we were booking a distance b&b....say, pretty much all of them were of the the same standard and price...one was 50% more...so I asked why?....it's about the 'experience', was the reply.
All we wanted a clean place good breakfast before hitting another round of trails



Mar 20, 2023 at 06:24 PM
hmzimelka
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p.1 #16 · p.1 #16 · Zeiss ZM Wobble - 2023 Edition..


thrice wrote:
My 35/1.4 ZM distagon is very difficult to focus compared to all Leica/Voigtlander lenses I own or have owned. It is also inconsistent indicating the lubricant is either not even or the helicoid is improperly machined but I would say more likely the former.




Unfortunately I haven't used the 35/1.4, and it's also the only ZM lens with a more complex helicoid focus system.
An uneven focus feel doesn't necessarily mean the lubrication isn't even or that the helicoid is at fault. It can be as simple as a guide with a minor imperfection. I've experienced a Planar 50mm that had the above discussed cut out, for the brass guide, slightly unevenly cut. It was slightly narrower at the top (infinity) than at the bottom (close focus) therefore focus feel was looser at close focus. This cut out had no visible issue, and it took some good quality vernier calibers to determine that it had differences in width. I presume the ring it's cut in was/is aluminium, it would be possible for the front of the ring to be deformed ever so slightly because the ring is open at the front by the cut out. The bottom of the ring still has sufficient support because the cut out terminates just over half way down the ring. It only takes a small fraction of a millimetre for the cut out width to influence the resistance of the tab moving up and down it and therefore influence the focus feel.

But the ZM Distagon 35/1.4 might be a different beast all together... I've not seen a repair guide for it yet.
But I doubt its any more complicated than the Ais Nikkor 55/2.8 Micro or the Ais Nikkor 85/1.4 which both have a CRC system, but aren't too complicated to disassemble... they just take longer due to having more parts.



Mar 21, 2023 at 01:06 AM
bluehawaii
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p.1 #17 · p.1 #17 · Zeiss ZM Wobble - 2023 Edition..


I was convinced by this 1 article that there was some complicated Teflon roller system inside the lens that had malfunctioned.

The author was describing a fantasy world that doesn't exist. There could well be a good reason for that; perhaps Zeiss completely changed the design of the focus mechanism at some stage during production. Although it seems highly unlikely.

With reference to the correct information that this 2 article and hmzimelka have kindly explained I would like to clarify some points..

Pictures are copyright Yukosteel Photo Equipment Blog.

If i've got anything wrong with the following description please correct me.

The outermost focus ring that we hold and rotate in order to focus the image before taking a picture is secured to the main focus ring by 3 black coloured screws. The lens has been disassembled some way in order to access these screws.

In the picture below you can see that the author has removed the 3 black coloured screws and the outermost focus ring and has set it down next to the helicoid mechanism.

https://yukosteel.files.wordpress.com/2021/06/sxt1z7726.jpg


In the picture above, at approx. 4 o'clock we can see what the author calls the "focus ring transmission". The bronze coloured piece secured to the main focusing ring by 2 black screws.

This "focus ring transmission" transmits your focus input to the helicoid mechanism.

As you rotate the focus ring back and fourth before taking a picture, any tiny gap in the contact points between this bronze coloured part of the focus ring transmission and the slot that it rides in will be detectable as play; free movement of the focus ring where no movement of the optical assembly and therefore focusing of the image is taking place.

If we look closely again at picture above. This time at the 9 o'clock and 3'oclock positions we can just see 2 more bronze coloured parts. What author refers to as "brass helicoid guiders". Each secured to opposite sides of the outer helicoid by 2 screws (invisible in this picture).

The picture below shows one of them removed.

https://yukosteel.files.wordpress.com/2021/06/sxt1z7638.jpg


Each one of these 2 parts looks slightly different, one has an "open middle grove" cut into it.

The author explains: "In my sample guider with open middle groove is located at opposite side, and it required slight deformation to make it just a tiny wider to eliminate focusing “lag”, but still narrow enough to easily slide inside its socket without noticeable friction."

So these parts are adjustable and can be tweaked or adjusted to eliminate focusing play or lag.

hmzimelka wrote:
Unfortunately I haven't used the 35/1.4, and it's also the only ZM lens with a more complex helicoid focus system.
An uneven focus feel doesn't necessarily mean the lubrication isn't even or that the helicoid is at fault. It can be as simple as a guide with a minor imperfection. I've experienced a Planar 50mm that had the above discussed cut out, for the brass guide, slightly unevenly cut. It was slightly narrower at the top (infinity) than at the bottom (close focus) therefore focus feel was looser at close focus. This cut out had no visible issue, and it
...Show more

So if there is inconsistent focus pressure, rather than backlash/play, then the "brass helicoid guiders" system may require repair, unless the 35mm f1.4 Distagon ZM has a different mechanism altogether rather than just the same design shown above but with extra helicoids for the floating element system. I'm wondering if the cut out in the focus guider acts like a spring so that the lens can still be focused even if it starts to tighten up at some point along it's travel?










Mar 22, 2023 at 08:14 AM
hmzimelka
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p.1 #18 · p.1 #18 · Zeiss ZM Wobble - 2023 Edition..


bluehawaii wrote:

I was convinced by this 1 article that there was some complicated Teflon roller system inside the lens that had malfunctioned.

The author was describing a fantasy world that doesn't exist. There could well be a good reason for that; perhaps Zeiss completely changed the design of the focus mechanism at some stage during production. Although it seems highly unlikely.

With reference to the correct information that this 2 article and hmzimelka have kindly explained I would like to clarify some points..

Pictures are copyright Yukosteel Photo Equipment Blog.

If i've got anything wrong with the following description please correct me.
...Show more

The culprit on my lenses with that focusing play was from the brass tab seen in the annotated image below.

https://www.martinzimelka.com/sample_images/sxt1z7726.jpg


The slotted brass guide seen in the second image is one of two guides which prevent the inner helicoid from rotating. These have not caused any issues on my end. Note that only one of the two helicoid guides are slotted. When this guide is worn or lacking tension, it should cause a little play in the optical block (the part of the lens with the aperture and silver bayonet mount) has a bit of rotational play.

It may also show itself during a large magnification Live View feed, where the image wobbles a little when changing focusing directions back and forth.

[edit] this last mentioned wobble can also be caused by insufficient grease packing in the helicoids, and a little slop will cause the optical block to wobble/jiggle ever so slightly when focus directional changes are applied.



Mar 23, 2023 at 08:18 AM
bluehawaii
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p.1 #19 · p.1 #19 · Zeiss ZM Wobble - 2023 Edition..


hmzimelka wrote:



The culprit on my lenses with that focusing play was from the brass tab seen in the annotated image below.

https://www.martinzimelka.com/sample_images/sxt1z7726.jpg


The slotted brass guide seen in the second image is one of two guides which prevent the inner helicoid from rotating. These have not caused any issues on my end. Note that only one of the two helicoid guides are slotted. When this guide is worn or lacking tension, it should cause a little play in the optical block (the part of the lens with the aperture and silver bayonet mount) has a bit of rotational play.

It may also show
...Show more

Ok great. And thanks for adding the final pieces to the puzzle regarding the function of the helicoid guiders. Yukosteel blog had to adjust those in one lens and in another it was the focus transmission requiring adjustment like yours.

So let’s assume we start off with a correctly lubricated lens with all of it’s other components error free and in good order...

Possible sources of unwanted lag or wobble in the system are:

a) 1x brass tab or “focus transmission” shown in the post directly above this one. There is one of these. Any play here is most likely to be felt while moving the focus ring back and fourth during focusing.

b) 2x brass helicoid guides or “brass helicoid guider”. There are 2 of these. Play in either or both of these is most likely to be felt when holding onto and wobbling the front lens hood bayonet area of the lens (and therefore the optical assembly) which should not have any play at all, or a seen as slightly shifting image while focusing through live view.

c) Loose retaining ring at the rear of the lens. This is the black coated internally threaded ring with 2 slots that surrounds the rear element. The very rearmost part of the lens when the lens is removed from the camera and focused at infinity. It’s function is to secure the optical assembly to the inner helicoid.

d) Loose focus ring screws as described 2 posts above (the ring of 3 black screws). One of the least likely things to ever happen provided they are fitted correctly as the lens is being assembled during production.

I was trying to work out how the retaining ring could possibly ever become loose. You mentioned earlier hmzimelka that this retaining ring is normally very tight and is locked in place by thread-locking compound. It occurred to me that the optional Zeiss or Voigtlander branded LH-6 lens shade needs pressing down while it is rotated counter clockwise to remove it from the lens. If you try to rotate and remove it without pressing in there could be great rotational torque exerted on the helicoid guiders and possibly cause the retaining ring to work loose? I can’t think of any other way the retaining ring could become loose during normal focusing.





Mar 24, 2023 at 02:16 PM





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