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Leica Screw Mount Lens Issue


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18 replies to this topic

#1 Timmyjoe

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Posted 02 March 2012 - 21:23

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Hi folks, wondering if anyone else has experienced this and know how to remedy it.

Got a Leica iiif that has had a CLA by Leica Germany, so I think it's in pretty good shape. Also got a Leica 5cm collapsable Summicron LTM to go with it. When I screw the lens onto the camera body, and get it nice and snug, the lens sticks when I try to focus it. The more I snug the lens down, the more the focus sticks. If I leave the lens just short of loose, the focus is silky smooth.

When I take this same lens, and screw it down tight to an LTM to M adapter, and then place the lens + adapter on a Leica M body, the focus is again silky smooth. What gives?

I can't see anything amiss with the iiif. Taking a flat edge along the whole surface of the lens mount flange on the camera body, shows no high or low spots. Can't figure this out. When the lens is tight on an adapter and then on an M body, silky smooth focus. When the lens is tight on the iiif, sticky focus.

Again, anyone else experience this and know how to deal with it?

Any and all info will be greatly appreciated. Thank you.

#2 luigi bertolotti

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Posted 02 March 2012 - 22:24

:confused: Strange behavior... expecially the difference with lens on LTM body and LTM adapter... : how is the focus knob ? can be it has some form of "friction", when pushed, onto the LTM body, while the thickness of the adapter avoids the same to happen on a M body ? :confused:

#3 Timmyjoe

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Posted 02 March 2012 - 22:50

Thanks Luigi, no, the focus knob has plenty of clearance.

Well, I've posted this on a number of different forums and one thing that I found out is that this is a common problem with the Leica iiif Red Dial. Seems the camera bodies weren't the straightest and flattest where the lens mount attaches to the body.

Because the lens flange gets slightly distorted when it is screwed down tightly to the slightly un-flat body, then the lens gets slightly distorted when it is screwed down tight to the lens flange. This causes the sticking in the focus action of the lens.

Edited by Timmyjoe, 02 March 2012 - 23:19.


#4 luigi bertolotti

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Posted 03 March 2012 - 12:32

Thanks... me too have a IIIf RD, but id does not suffer of this issue with the Elmar and neither with the Summarit... I haven't a Summicron in SM... I wonder if this is significant of a question of "play" in the Summicron's focus helicoid... have you some other SM lenses to check this ?

#5 jc_braconi

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Posted 03 March 2012 - 14:13

I trie with different IIIf's Red Scale and different Summicron's
I do not encouter any change in tightening hard or not.
Can you post the s/n of both the camera and the Summicron ?
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#6 Timmyjoe

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Posted 03 March 2012 - 17:06

Camera is 639XXX and the lens is 121XXXX. As I mentioned, I posted this on a few different forums and the info I have gotten so far leads me to believe the lens flange on the camera is not flat. As the lens works fine with an LTM to M adapter on a few different M cameras I have tested.

From what I've been able to gather, when the camera is reassembled, if the camera tech doesn't assemble the front plate in a very particular order, the front plate will not be flat. Then when you attach the lens mount flange ring to the front plate, the lens mount flange ring will not be flat. Then when you screw on the LTM lens to the not flat lens mount flange, that puts torque on the lens, making it stick.

Still researching, but that is what I have found so far.

#7 jc_braconi

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Posted 03 March 2012 - 18:40

Camera is 639XXX and the lens is 121XXXX. As I mentioned, I posted this on a few different forums and the info I have gotten so far leads me to believe the lens flange on the camera is not flat. As the lens works fine with an LTM to M adapter on a few different M cameras I have tested.

From what I've been able to gather, when the camera is reassembled, if the camera tech doesn't assemble the front plate in a very particular order, the front plate will not be flat. Then when you attach the lens mount flange ring to the front plate, the lens mount flange ring will not be flat. Then when you screw on the LTM lens to the not flat lens mount flange, that puts torque on the lens, making it stick.

Still researching, but that is what I have found so far.

There is only one way to attach the front flange to the camera
you can see this little cut on the flange at 9 oclock it is easy to check if the front plate is flat or not using a rule or using black grease on the front flange you wil see when you screw on the lens and next unscrew
if all the grease was removed the flange is flat and if some grease is left there is where is the part unflat.
the front flange is strong on the IIIf cannot believe it is torqued on yours
what about the focusing lever or wheel, in the camera ?
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#8 telewatt

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Posted 03 March 2012 - 19:06

Camera is 639XXX and the lens is 121XXXX. As I mentioned, I posted this on a few different forums and the info I have gotten so far leads me to believe the lens flange on the camera is not flat. As the lens works fine with an LTM to M adapter on a few different M cameras I have tested.

From what I've been able to gather, when the camera is reassembled, if the camera tech doesn't assemble the front plate in a very particular order, the front plate will not be flat. Then when you attach the lens mount flange ring to the front plate, the lens mount flange ring will not be flat. Then when you screw on the LTM lens to the not flat lens mount flange, that puts torque on the lens, making it stick.

Still researching, but that is what I have found so far.


:confused:...What I can imagine too, is that the role for the transmission the distance for the viewfinder stuck.

regards,
Jan
scheffner-foto.de

#9 doubice

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Posted 03 March 2012 - 19:10

I believe the issue is that the lens mount is not perfectly flat. This could be for two reasons - either some washers missing under the lens mount or, a warped body. By tightening the lens, uneven force is applied to its helicoid and thus the focusing action becomes 'sticky'. The only way to check this exactly, would be using a depth measuring micrometer (body lens mount vis-a-vis pressure plate) or a collimator.

I have had a similar issue with a 1.5/50mm Summarit and it only happened on one body, when the lens was tight in the mount. I paid no attention to it, as I had a few other bodies where the problem was not present..... ;)

Best,

Jan

#10 Timmyjoe

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Posted 03 March 2012 - 19:17

JC, you misunderstood my post. You are correct, there is only one way to attach the front flange to the camera, but the front flange is attached to the front plate. If the front plate is not flat, then the flange will not be flat. When attaching the front plate, part of the sub assembly must be loosened, the front plate attached, then the sub assembly re-tightened. If this doesn't happen, according to a couple of repair techs I talked to, then the front plate will be "warped" or not flat. This will make the front flange, which attaches to it, not flat. And when the lens is screwed down to the front flange, it being not flat will put torque on the lens mount, which causes the binding.

The focus lever and wheel move quite freely in my iiif. And the lens focuses smoothly as long as I don't tighten it down on the camera. So if it is slightly loose, it focuses smoothly, but tighten it up 1/8th of a turn and the focus becomes sticky.

#11 Timmyjoe

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Posted 03 March 2012 - 19:25

Lens mount Flange is not flat. Just put magic marker all around the lens mount, let it dry, and screwed the lens onto the camera. When I removed the lens, the magic marker was removed from the right and left sides of the lens mount, but still present at the top and bottom of the lens mount. So it's obviously not flat.

Here's what the National Camera service manual for the iiif says about mounting the front plate:

"The screw at the bottom of the front plate (which is slightly shorter in length than the other four front plate screws (I believe this is screw G)) and the uppermost screw around the lens opening (I believe this is screw D) both pass into anchor plates on the inside of the focal plane. Before installing these two, loosen the screws which secure the anchor plates (one at the end of the flat retard rod spring and two within the accessory shoe cavity). Now, align the threaded holes in the anchor plates with their corresponding holes in the front plate and replace the two front plate screws. Tighten down the anchor plates once again and install the remaining three screws around the lens opening which thread into the light shields."

Here's an image of the front plate with the screws identified by letter.


Attached File  Plate.jpg   91.81KB   163 downloads


Edited by Timmyjoe, 03 March 2012 - 19:32.


#12 pico

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Posted 03 March 2012 - 20:14

Tim, I think you are onto the problem. Unfortunately you will have to remove some covering to get at all the screws - or am I wrong?

There should be a paragraph describing the torque required for each fastener and the sequence for tightening them. Follow carefully. A screw overtightened is already half-broken.
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#13 jc_braconi

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Posted 04 March 2012 - 02:19

There should be a paragraph describing the torque required for each fastener and the sequence for tightening them. Follow carefully. A screw overtightened is already half-broken.
.

remember to use some grease/lubricant on the screws threads this help tightening especially in dry metals.
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#14 Timmyjoe

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Posted 04 March 2012 - 03:40

Well it turns out that, as usual, things are a bit more complicated than they originally appeared. Here is what I found out and what I did to remedy the problem.

I posted this on a number of forums, and a camera service person commented that he had seen this before, and he said in particular on iiif cameras serviced at the factory. Seems that when you are reassembling the camera, and you are putting the front plate on, you need to go back and loosen a couple of brackets you've already tightened, otherwise you put undo torque on the front plate, causing it to twist and not sit flat.

That twist is transmitted to the lens mount flange, which transmits the twist to the lens when it is mounted, which binds up the lens. That's my understanding at least.

I found the information and image I posted above in the National Camera service manual for the iiif. Again, here is how they tell you to reassemble the front plate.

"The screw at the bottom of the front plate (which is slightly shorter in length than the other four front plate screws (screw G)) and the uppermost screw around the lens opening (screw D) both pass into anchor plates on the inside of the focal plane. Before installing these two, loosen the screws which secure the anchor plates (one at the end of the flat retard rod spring and two within the accessory shoe cavity). Now, align the threaded holes in the anchor plates with their corresponding holes in the front plate and replace the two front plate screws. Tighten down the anchor plates once again and install the remaining three screws around the lens opening which thread into the light shields."

Here's an image of the front plate with the screws identified by letter.

Attached File  Plate.jpg   91.81KB   144 downloads


On my camera I found out I could remedy this by taking the camera apart, loosening screw D and G and then loosening the anchor plate screws, then tightening screw D and G, and then tightening the anchor plate screws?

I then put the camera back together, reset the FFD with a collimator, and reset the rangefinder at infinity. Now she focuses nice and smooth.

Very Happy.

Thanks to everyone for your input.
  • telewatt said thank you to this

#15 pico

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Posted 04 March 2012 - 04:17

remember to use some grease/lubricant on the screws threads this help tightening especially in dry metals.


Wrong! Torque specs presume clean dry surfaces or you will over-torque the part!
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#16 jc_braconi

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Posted 04 March 2012 - 15:30

Wrong! Torque specs presume clean dry surfaces or you will over-torque the part!
.

Do this and you will galling the 2 parts !!! But after all make your own ....
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#17 jc_braconi

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Posted 04 March 2012 - 15:34

I found the information and image I posted above in the National Camera service manual for the iiif..


I own this book Nat Cam Manual # 327 from 1969 by Larry Lyells the sketch is on page 32
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#18 pico

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Posted 04 March 2012 - 18:06

Do this and you will galling the 2 parts !!! But after all make your own ....


:) Making those tiny screws is beyond me. But seriously, is there a different procedure for camera fasteners? Lubricating a fastener permits higher, possibly damaging torque.

I use anti-seize lube on large high-carbon fasteners, but nothing else. Aside - I was quite surprised to find a jointed bicycle mirror that appears to use small brass fasteners that use crush nuts to discourage movement without resorting to an anaerobic locking fluid. (Crush fasteners are ever-so-slightly oval and can be used only once.)

#19 jc_braconi

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Posted 04 March 2012 - 18:21

Do this and you will galling the 2 parts !!! But after all make your own ....


:) Making those tiny screws is beyond me. .)



Process... not screws:rolleyes:. for the rest I am too lazy to write long post :cool: I let this to Luigi :)
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