Canon 50mm f1.2 LTM Repair Option

[Miles.]

Hi all,

As many here know, the Canon 50mm f1.2 LTM lens is infamous for suffering from a type of haze/element degradation that, more often than not, cannot be solved with a simple CLA.

Some years ago I became aware that Kanto Camera, a preeminent repair shop in Japan, offers a remanufactured element that can be replaced during a CLA. Just this year, after failing to find a “nice” copy of a 1.2, I finally sent mine in for the service.

Today, just 6-months after I first mailed my lens, it arrived safely back in Portland.

Kanto Camera charged $250 USD for a CLA and the replacement element. Considering that this service isn’t available anywhere else in the world, I figure that’s a pretty nice deal.

I’m not affiliated with Kanto Camera but I think it’s important to highlight these type of repair opportunities, particularly when you must assume this service won’t be possible forever.

Pictured is my lens with the “bad” element removed.

 

[Sonnar Brian]

I know this problem well! Went through three Canon 50/1.2's and finally got one with clean glass. They are amazing lenses. Well worth the $250 CLA.

The original dream Lens?

 

[Miles.]

The original dream Lens?

It’s certainly the working class LTM dream lens!

- Canon 5cm f1.2: $250
- Fujinon 5cm f1.2: $10,000?
- Zunow 5cm f1.1: $5,000?
- Nikkor 5cm f1.1: $12,000?

 

[Sonnar Brian]

The price on the Nikkor 5cm F1.1 is way down- I've seen them under $3K.
The Zunow 5cm F1.1: buy the 7artisans 50/1.1 instead. Same basic optical formula as the V2 Zunow 5cm F1.1.
Wide-Open, 7Art 50F1.1

 

[Mackinaw]

Pictured is my lens with the “bad” element removed.

So Kanto returned the bad element? I've been thinking about having this done to my 50/1.2. As for Kanto, I've had them perform CLA's on a few of my cameras over the years. They do exemplary work.

Jim B.

 

[Miles.]

So Kanto returned the bad element? I've been thinking about having this done to my 50/1.2. As for Kanto, I've had them perform CLA's on a few of my cameras over the years. They do exemplary work.

Jim B.

I asked for it back as a curiosity… figured it might be neat to share here!

 

[splitimageview]

That's a deal!

 

[Sonnar2]

Which element is it and which refractive index has it? (should be equal to the original)

 

[Miles.]

Which element is it and which refractive index has it?

Kanto calls it the G5 element, and I'm not sure.

 

[wjlapier]

That’s great info. I have this lens and will send it to Kanto for the CLA and inspection. 6 months and cost is reasonable. Thank you for sharing.

 

[aw614]

I got mine back yesterday from Kanto Camera, can't wait to shoot it. Just had to mount it on my IIIC 😀 but it looks quite nice on my Canon L1

 

[Sonnar Brian]

I ended up buying Miles Canon 50/1.2, and compared it with my "mint glass" original 50/1.2.

Quick Comparison: Kanto Repaired Canon 50mm F1.2 and all-original/mint glass early Canon 50/1.2

I went through several Canon 50mm F1.2 lenses to get one with clean glass, an earlier lens bought on a Canon Vt Deluxe. This lens has perfect glass, no coating damage, no hazing, no balsam discoloration, and no etching on the glass. It gives great results. Last month a Canon 50mm F1.2 that had...

rangefinderforum.com

The Kanto repaired lens has the edge. Better than new.

 

[qqphotos]

I somehow managed, without even being aware of the issue, to end up with one of these that does not have the haze, but it's good to know there's an option should it develop. I feel like I need an extra barnack body to adjust to this lens, though.

 

[qqphotos]

Which brings up another question - the copy I have produces sharp focus (well, as sharp as this lens ever gets at f/1.2) consistently about 10-12 cm closer than the rangefinder thinks is correct, when wide open and at 1.5 meters distance. I expected some discrepancy but this is wildly off by enough that I suspect either it's shimmed wrong or has been disassembled and put back wrong.

It looks like that Canon bodies' flange distance is the same 28.8mm as Leica's, and my Barnack bodies focus other lenses well enough, so that leaves me suspecting the lens needs to be de-shimmed (i think?) which is unfortunate since there aren't any shims in it.

 

[Sonnar Brian]

It sounds like the lens has been re-assembled incorrectly, or might be made from mismatched parts.
10cm too close at 1.5cm- if the helical were misthreaded, I would expect the problem to be much worse.
One of the elements could be loose- which would cause an error.
If all are tight, could be a lens made from "the best one of two", but needed some work. IF this is the case, unscrew the rear group to move closer to the image plane. If that fixes the problem, use a small shim to hold the position. I've used thin wires, paper, copper tape, etc.

 

[qqphotos]

It sounds like the lens has been re-assembled incorrectly, or might be made from mismatched parts.
10cm too close at 1.5cm- if the helical were misthreaded, I would expect the problem to be much worse.
One of the elements could be loose- which would cause an error.
If all are tight, could be a lens made from "the best one of two", but needed some work. IF this is the case, unscrew the rear group to move closer to the image plane. If that fixes the problem, use a small shim to hold the position. I've used thin wires, paper, copper tape, etc.

Thank you - it's very helpful to know that it would be worse if it were a misthreaded helical! It's rather painstaking work doing this with film but I'll try a couple more rounds and then try to borrow a digital M body 🙂

 

[peterm1]

Thank you - it's very helpful to know that it would be worse if it were a misthreaded helical! It's rather painstaking work doing this with film but I'll try a couple more rounds and then try to borrow a digital M body 🙂

I had a very similar issue with the Canon LTM 50mm f1.2 lens - front focusing probably by a similar amount IIRC. Here is the saga...........

The lens has a couple of internal brass shims which adjust the point of focus. After much trial and error and discussion with my camera guy (a highly experienced man trained in old lenses and since retired - sadly) we agreed that for some God forsaken reason one of the shims was too thick. When I bought the lens it evidently had many years of "good" use (its condition told me as much) so I cannot conceive how the shim could have been wrong for all these years. It could not have come from the factory with such an error - otherwise how would it have seen such use on a rangefinder camera (and which would also beg a question about Canon's quality assurance processes.) I concluded that somewhere in its history, somehow the shim was swapped out and the wrong one put in.

Fortunately it was a simple (though tedious) task to fix. Remove the shim and lay the offending brass shim on a flat diamond lapping plate and carefully lap it to the correct thickness - rotating the shim constantly and consistently as you go to make sure it is not thicker or thinner in any dimension or orientation. Check, rinse and repeat - time and time and time again. With an hour or more of careful lapping in this manner to reduce its thickness (accompanied by many sequences of temporary reassembly and testing on an M8 using its rangefinder to test the point of focus at a measured distance), eventually the lens was returned to tolerance as regards focusing. You can do it yourself if you have some basic skills and patience or have a tech do it for the appropriate fee. BTW if you have not disassembled this lens it also has the virtue of being one of the simplest lenses I have ever disassembled to this degree - which as the helicoid does not have to be messed with is not very much.

I still am much mystified as to how this lens got so far out of whack. But as it now works perfectly I have given up on worrying about it. though part of me would still like to know.

 

[qqphotos]

I had a very similar issue with the Canon LTM 50mm f1.2 lens - front focusing probably by a similar amount IIRC. Here is the saga...........

The lens has a couple of internal brass shims which adjust the point of focus. After much trial and error and discussion with my camera guy (a highly experienced man trained in old lenses and since retired - sadly) we agreed that for some God forsaken reason one of the shims was too thick. When I bought the lens it evidently had many years of "good" use (its condition told me as much) so I cannot conceive how the shim could have been wrong for all these years. It could not have come from the factory with such an error - otherwise how would it have seen such use on a rangefinder camera (and which would also beg a question about Canon's quality assurance processes.) I concluded that somewhere in its history, somehow the shim was swapped out and the wrong one put in.

Fortunately it was a simple (though tedious) task to fix. Remove the shim and lay the offending brass shim on a flat diamond lapping plate and carefully lap it to the correct thickness - rotating the shim constantly and consistently as you go to make sure it is not thicker or thinner in any dimension or orientation. Check, rinse and repeat - time and time and time again. With an hour or more of careful lapping in this manner to reduce its thickness (accompanied by many sequences of temporary reassembly and testing on an M8 using its rangefinder to test the point of focus at a measured distance), eventually the lens was returned to tolerance as regards focusing. You can do it yourself if you have some basic skills and patience or have a tech do it for the appropriate fee. BTW if you have not disassembled this lens it also has the virtue of being one of the simplest lenses I have ever disassembled to this degree - which as the helicoid does not have to be messed with is not very much.

I still am much mystified as to how this lens got so far out of whack. But as it now works perfectly I have given up on worrying about it. though part of me would still like to know.

That's quite a conundrum. It's hard to imagine anything other than a flubbed repair attempt being responsible. I'm hoping not to perpetrate yet another of those so I'll probably hold off actually removing material until I can accurately characterize the miscalibration, which is pretty challenging!

 

[Sonnar Brian]

@qqphotos
You originally wrote that your lens does not have any shims in it. The Canon 50/1.2,and most Canon RF lenses use shims for calibration.
Have you taken the barrel out of the mount to verify that it does not have any shims? If it does- might be as simple as removing one, multiple shims of different thicknesses are often used.

 

[peterm1]

Which brings up another question - the copy I have produces sharp focus (well, as sharp as this lens ever gets at f/1.2) consistently about 10-12 cm closer than the rangefinder thinks is correct, when wide open and at 1.5 meters distance. I expected some discrepancy but this is wildly off by enough that I suspect either it's shimmed wrong or has been disassembled and put back wrong.

It looks like that Canon bodies' flange distance is the same 28.8mm as Leica's, and my Barnack bodies focus other lenses well enough, so that leaves me suspecting the lens needs to be de-shimmed (i think?) which is unfortunate since there aren't any shims in it.

I forgot to mention this before but will do so now. You say that the lens has no shims in it. Have you disassembled and eyeballed it to confirm? If so this is mystifying as it would normally be expected as Sonnar Brian points out. Also, without shims I would expect the lens to be focusing further away than expected, not closer were it a calibration issue due to something to do with the shims. On reflection, this does I think suggest a possible cause other than the problem I had. It also means that reshimming would not work if the lens is already focusing too close. Addition of shims in the lens' current state would push the optical units even further out of their correct position making it focus even closer than it does now.

This suggests to me that the possible culprit in this case might be that the helicoid was disassembled and relubed (a common enough procedure with old lenses in which the helicoid grease has hardened over time) and then reassembled incorrectly by starting the helicoid in the wrong position during reassembly - a common enough issue if undertaken by an enthusiastic amateur who forgot to make "witness" marks on the helicoids to mark how they were aligned when they came apart during disassembly. Having said this, I would expect this to be obvious the first time the lens was actually used on a rangefinder camera after the relube. Correcting it then becomes a matter of trial and error to fix it - a long and frustrating annoyance. (Believe me - I made this mistake once - and once bitten, twice shy as the old adage goes.) Possibly an earlier owner did this and realizing his error and lacking the skill, knowledge or patience to correct it, just decided to sell it on without declaring the issue. Which sadly is also a common enough issue in second-hand markets.

I have attached a link below to a tutorial on how to CLA this lens. It is a reasonably simple process to disasseble the lens. If you scroll down a little to the 2nd picture in the section labelled "Part One" you will see a brass collar surrounding the optical unit. I think this is one of the shims that I would expect to find there to space the optical unit correctly. If yours are missing that would probably be a further complicating factor - maybe also the product of a prior owner's ham-fisted disassembly and cleaning attempt. Jokes about parts being left over following attempts to repair car engines, camera bodies, camera lenses etc. are only amusing because they can too often be true.

DIY: Cleaning a Canon 1.2/50mm rangefinder lens - Asser Stadsfotograaf

On the net you can find all kinds of stories on this lens. Most say its very soft wide open, prone to flare and what else. But most of the time this is merely a side effect from shooting a 50+ year old lens that has gotten hazy inside. Most of these lenses have scratches … Continue reading "DIY...

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