lens repair, modification and disassembly guide thread
/forum/topic/1159122/3

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Thatspeck
Registered: Dec 13, 2003
Total Posts: 741
Country: United States

I don't know of a kit being offered specifically for G conversions. Hawks has a bare helicoid FS here that will RF couple with most 50mm (really 51.6mm) optical blocks that would fit it. He's only listing two diameter measurements so it's a bit of a gamble how things would fit. Even the 45G would need the RF coupling tweeked as well as an unknown amount of "fitting". I sent a message through that listing for more measurements but haven't heard back for three weeks+
Jieying-USA on Ebay has had several M converted 21G's FS recently along with pics of all the G lenses converted in similar fashion, pretty nice job. He did respond to my query and is not interested in taking in conversion work at this time. Please keep your eyes out for other interesting G conversions and post them here

Edit: Jieying-USA is now converting Contax G lenses to order. I gave up on my own conversion and sent him my 45G before I screwed it up any further, three days later it was back in the mail to me. Very nice quality new parts, fully rangefinder coupled and calibrated to Leica M bodies. Focus feel is silky smooth (with the addition of a little of my own "Pedro's synlube"). Focus ring is a little too close to the body but eventually I'll add some kind of a tab to it which should solve that. No zone focus scale but RF calibration is spot on.



JimBuchanan
Registered: Jan 11, 2006
Total Posts: 1448
Country: United States

Thatspeck wrote:
Jieying-USA on Ebay has had several M converted 21G's FS recently along with pics of all the G lenses...


He claims to use the original plastic helical of the G lens, operated by the outside visible focus ring grip. Similar to your theory of using the original plastic helical with a slot/tab arrangement. I'd like to know how smooth it works. And he says it turns in the correct direction like Leica.



Thatspeck
Registered: Dec 13, 2003
Total Posts: 741
Country: United States

Hey Jim, which of the G lenses have a plastic helical? I've only been inside the black 45G I have, it's helicoid is almost definitely anodized black aluminum (I scraped at it a bit). I checked back on Jieying's feedback and doesn't appear any has been left yet for that G90 or the others that have sold, he has a 45 and 28 on there right now. The focus ring right up against the body does look a little awkward. Makes me wonder what kind of a market there might be for such a kit (or service), hint, hint...



JimBuchanan
Registered: Jan 11, 2006
Total Posts: 1448
Country: United States

I thought the 45G I disassembled had a plastic helical, but I could be wrong. It was a coarse thread and light weight in order to not require as much ratchet torque of the screw drive. That is why I wonder about his method.

The big draw for me is the M mount, as I would like to standardize on the mount. Short of that, I would like to try mounting a G28 in a Minolta body/E bayonet like Sebboh has done.



carstenw
Registered: Dec 26, 2005
Total Posts: 15290
Country: Germany

Well, today was a very happy day for me: I was able to open and clean not one, but two lenses which I have bought for very nice prices, but which had "fog" inside.

The first was an XPan 90mm lens I bought many months ago, and since I had never attempted anything like this, I was reluctant to risk a few hundred Euro on a botched job.

The saviour came in the form of an RZ67 Sekor Z 127mm lens which I just picked up for almost nothing, and which had the same problem. It appeared to have some fog somewhere inside near the rear of the lens, so naturally I looked at the rear first, and found a notched ring, which I was able to remove with a normal spanner, something like this:

http://www.micro-tools.de/en/Spanner-Wrenches-oxid/Spanner-Wrench-Economy-Slotted.html

However, after that nothing went anywhere, so I put it on again and started looking from the front. There was also a notched ring, but trying the spanner on it only made clear that it bumped against something in front of it. I looked at it unknowingly for a while, and eventually realised that the whole front plate was one piece screwed into the body, and I was then able to remove that plate with a rubber stopper, something like this:

http://www.micro-tools.de/en/Lens-Tools-oxid-1/Lens-Ring-Tool-Kit.html

After that, trying the spanner again got me not the inner ring loose, which is was meant to, but a whole assembly of the front few elements, probably up to the aperture or shutter. A quick look with an LED flashlight showed that there was a problem, which looked like it might be on the rear element. Cleaning it proved this right. Then I looked at the front element of the remaining group in the body, and it was also dirty. Cleaning that was a bit tricky, being still in the body, but I managed, and after putting everything back together carefully, the lens is now nearly as clean as when it left the factory! Yay!

This gave me the guts to try the 90mm XPan lens again. This time, the fog was very fine-grained and dense, and looked to be on the inside of the rear element, so I tried the first ring with the spanner, which came out readily. The lens wouldn't come out though, so I proceeded to remove the next thing as well, which was the whole rear group. After getting this out, I was able to get the lens out with a couple of taps. Cleaning it on the inside and the rear surface of the lens in front of it cured it as well. Putting it back together was made slightly more complicated by the fact that when the lens hopped out, it turned a couple of times so I wasn't sure which way was right, but luckily one side was very concave and the other slightly convex, and I do recall that the outer surface was convex, so it went back together again after all.

Now I have two great new lenses to try out, and one less todo item on my list

Photos supplied on request.

If I ever need to do something like this again, I will buy another couple of high-quality spanners, and a couple of different sizes of suction cups. This should make it easier to open things and remove elements.



sebboh
Registered: Nov 02, 2009
Total Posts: 10200
Country: United States

^^ sounds great carsten!

what did you use to clean out the fogging?



sebboh
Registered: Nov 02, 2009
Total Posts: 10200
Country: United States

since there has been a bit of debate at what is the best way to reduce the retaining ring on the rokkor 58/1.2, i made a video how to of the retaining ring removal.

here is a little writeup to go with it:

1) Remove the 4 long screws from the mount of the lens. DO NOT remove the 4 short screws as doing so will dramatically complicate the disassembly. If the lens has already been converted to Canon (or Nikon, or Pentax, or Sony) mount, only the 4 long screws will be present. If the lens still has the original minolta mount, long and short screws will alternate around the lens mount.

2) Gently pull off the mount making sure that the aperture ring does not come up along with it (or you run the risk of losing the ball bearing that holds the aperture ring at click stops). Be sure to pay attention to the orientation of the mount for when you reattach it. If the lens has the original mount, the spacer will come off with the mount since they are attached by the 4 short screws. If the lens has already been converted to another mount, the spacer will probably remain behind and you should lift it off next.

3) Unscrew the rear optical assembly. Simply grasp the optical assembly firmly and turn it counter clockwise until it can be lifted free of the rest of the lens. Turn the rest of the lens over to prevent dust falling down into the lens internals.

4) Unscrew the rear retaining ring on the back of the rear optical assembly. Simply grasp the optical assembly firmly in one hand and the retaining ring in the other and turn the retaining ring counter clockwise till it comes free. Now you can do what you will to the retaining ring without risking the glass. Place the optical assembly internal side down to prevent dust from getting on the internal surface. Do not separate any of the optical elements in the rear optical assembly unless you wish to clean them.

Hint: I find that the optical assembly and retaining ring are too small to easily grip in my bare hands. Wearing surgical gloves or dish gloves makes it much easier.



carstenw
Registered: Dec 26, 2005
Total Posts: 15290
Country: Germany

sebboh wrote:
^^ sounds great carsten!

what did you use to clean out the fogging?


Eclipse lens/sensor cleaning fluid. It wasn't mold or fungus, perhaps oil or water vapour? I am not so knowledgeable on this. It really looked like dense white fog.



telyt
Registered: Mar 01, 2004
Total Posts: 1704
Country: United States

Earlier this year I purchased a Leitz/Novoflex 560mm f/6.8 Telyt on the Novoflex PIGRIFF-C rapid-focus grip, and at the same time I found on the big auction website a very inexpensive Novoflex 400mm f/5.6 T-Noflexar lens head to fit the PIFGRIF-C. It was a few weeks after the 400 arrived before I could test it adequately and immediately found out why it was so inexpensive: the image quality was HORRIBLE. It was so bad that I couldn't discern a plane of focus through the viewfinder.

My previous experience with 2 samples of this model lens was much better so I figured something was messed up on this sample. It's a simple 3-element achromat, there's not much that can go wrong, but I can't imagine it was supposed to be this bad.

Upon disassembly I noticed scratches in the retaining ring holding the rear element in place and guessed that some doofus had taken it apart and re-assembled it wrong. After a few minutes with my tools I had reversed the rear element, re-assembled and confirmed my hypothesis

Results:



telyt
Registered: Mar 01, 2004
Total Posts: 1704
Country: United States

A few years ago I did a stupid and had to send my Leica 280mm f/4 APO to Leica in Germany to replace the front element. Four months later it returned with a new front element, and with the aperture mechanism disconnected from the aperture ring!

Rather than send the lens away again I got my tools out. The module with the flange and aperture ring is held onto the lens barrel with four long screws:



The linkage between the aperture ring and the aperture blades is simplicity itself, a single lever. Remove the flange/ring module, line up the lever on the module with the corresponding slot in the aperture blade module and re-assemble. If I can do it why couldn't Leica in Germany do it?!?






zhangyue
Registered: Jan 28, 2011
Total Posts: 2692
Country: United States

Great thread with many great posts! It is not often see info like this anywhere.



ken.vs.ryu
Registered: Apr 24, 2005
Total Posts: 3461
Country: N/A

How is the lens on a minolta sebboh?



sebboh
Registered: Nov 02, 2009
Total Posts: 10200
Country: United States

ken.vs.ryu wrote:
How is the lens on a minolta sebboh?


awesome.


telyt thanks for the description and photos!



ZoneV
Registered: Nov 20, 2008
Total Posts: 887
Country: Germany

I made a 6 mm thin Canon EF extension tube - it is full manual as my first homemade EF extension tube.
But first experiments with full electronic communication contacts work well.
I am happy to achieve 6mm thickness, this is perfect for many lenses like the Zeiss Distagon 35mm/1.4, and good enough for others.



Furthermore I made a Konica Minolta Sony A to Canon EF mount adapter. This has no real need for me - until I get a cheap Sony STF 135mm lens for comparison images :-)



KOJI
Registered: Jan 07, 2006
Total Posts: 93
Country: Canada

JimBuchanan wrote:
I thought the 45G I disassembled had a plastic helical, but I could be wrong. It was a coarse thread and light weight in order to not require as much ratchet torque of the screw drive. That is why I wonder about his method.

The big draw for me is the M mount, as I would like to standardize on the mount. Short of that, I would like to try mounting a G28 in a Minolta body/E bayonet like Sebboh has done.


45G's helical is aluminum for the lens optical block,
the holding helical (of the body side) is plastic.



KOJI
Registered: Jan 07, 2006
Total Posts: 93
Country: Canada

Thatspeck wrote:
I don't know of a kit being offered specifically for G conversions. Hawks has a bare helicoid FS here that will RF couple with most 50mm (really 51.6mm) optical blocks that would fit it. He's only listing two diameter measurements so it's a bit of a gamble how things would fit. Even the 45G would need the RF coupling tweeked as well as an unknown amount of "fitting". I sent a message through that listing for more measurements but haven't heard back for three weeks+
Jieying-USA on Ebay has had several M converted 21G's FS recently along with pics of all the G lenses converted in similar fashion, pretty nice job. He did respond to my query and is not interested in taking in conversion work at this time. Please keep your eyes out for other interesting G conversions and post them here

Edit: Jieying-USA is now converting Contax G lenses to order. I gave up on my own conversion and sent him my 45G before I screwed it up any further, three days later it was back in the mail to me. Very nice quality new parts, fully rangefinder coupled and calibrated to Leica M bodies. Focus feel is silky smooth (with the addition of a little of my own "Pedro's synlube"). Focus ring is a little too close to the body but eventually I'll add some kind of a tab to it which should solve that. No zone focus scale but RF calibration is spot on.


Here is one: http://www.pbase.com/kkawakami/lens_mods_g_planar_45mm_to_m
(The above does not have RF-coupling, I do not need it.)

Another one: http://www.pbase.com/kkawakami/lens_mods_g_sonnar_90mm_to_f
(For F-mount conversion)

See any other 1,700 fix or modifications: http://www.4photos.de/camera-diy/index-en.html



XFer
Registered: Feb 12, 2013
Total Posts: 1
Country: Italy

Hello everyone, this is my first message.

First of all thank you all, I've learned a lot of things here!

I have a G1 and G2, with various lenses (28, 45, 2x90).

To cut short a long story: nearly all my lenses have varying focusing issues, on both bodies.

And no, it's not operator error; I don't have the time to explain all the tests I've done, but I'm rock sure it's indeed a camera/lens issue.
I've also calibrated the rangefinder on both bodies (both active and passive on the G2), so that's not the issue either.

I'm quite sure that, at this point, the camera measures the right distance and moves the focusing screw accordingly.

So the issue is, almost 100% sure, with the lenses.
And, in fact, each lens has a different issue (one frontfocuses, the other backfocuses, one is more or less OK etc.).

Now: I'm quite sure G lenses can be focus-calibrated.
Maybe they have internal shims which can be replaced/added/removed, or maybe (with lot of luck) they have adjusting screws/helicoids/whatever.

So the question is: has anyone dismantled a G lens?
Is there some sort of step-by-step tutorial about disassembling a G lens?
To whom have successfully disassembled a G lens: did you see any kind of shim/screw/adjustment related to focus?

Thanks a lot!

In return, if/when I'll successfully fix the focus issue on my lenses, I'll explain how.

Fernando



Phillip Reeve
Registered: Sep 17, 2011
Total Posts: 1469
Country: Germany

sebboh wrote:
since there has been a bit of debate at what is the best way to reduce the retaining ring on the rokkor 58/1.2, i made a video how to of the retaining ring removal.
4) Unscrew the rear retaining ring on the back of the rear optical assembly. Simply grasp the optical assembly firmly in one hand and the retaining ring in the other and turn the retaining ring counter clockwise till it comes free. Now you can do what you will to the retaining ring without risking the glass. Place the optical assembly internal side down to prevent dust from getting on the internal surface. Do not separate any of the optical elements in the rear optical assembly unless you wish to clean them.

Hint: I find that the optical assembly and retaining ring are too small to easily grip in my bare hands. Wearing surgical gloves or dish gloves makes it much easier.

how much force did you have to apply when unscrewing the rear retaining ring? I just tried barehanded and wasn't successful.



sebboh
Registered: Nov 02, 2009
Total Posts: 10200
Country: United States

Phillip Reeve wrote:
sebboh wrote:
Hint: I find that the optical assembly and retaining ring are too small to easily grip in my bare hands. Wearing surgical gloves or dish gloves makes it much easier.

how much force did you have to apply when unscrewing the rear retaining ring? I just tried barehanded and wasn't successful.


it's quite hard to do bare handed if you have adult sized hands, especially if it hasn't been unscrewed in 50 years. with gloves on it is much easier to grip and your force can be concentrated on turning rather than squeezing and moderate force will usually do the trick. don't try to use any sort of metal gripping device as you could easily damage the ring/glass. if the ring looks like it has already been modified to some degree by somebody else, be aware that it might have been glued.



Phillip Reeve
Registered: Sep 17, 2011
Total Posts: 1469
Country: Germany

sebboh wrote:
Phillip Reeve wrote:
sebboh wrote:
Hint: I find that the optical assembly and retaining ring are too small to easily grip in my bare hands. Wearing surgical gloves or dish gloves makes it much easier.

how much force did you have to apply when unscrewing the rear retaining ring? I just tried barehanded and wasn't successful.


it's quite hard to do bare handed if you have adult sized hands, especially if it hasn't been unscrewed in 50 years. with gloves on it is much easier to grip and your force can be concentrated on turning rather than squeezing and moderate force will usually do the trick. don't try to use any sort of metal gripping device as you could easily damage the ring/glass. if the ring looks like it has already been modified to some degree by somebody else, be aware that it might have been glued.

it looks as if it was glued :-(



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