Canon 50 f1.8 LTM need advice on cleaning

[trondareo]

I bought this lens on a whim last year, but found it was very soft and full of gunk (see pics)
Has anyone got experience with dismantling these? Are they worth sending away? Should I give it up and only use it for photographing pimply youths? 😉

 

[trondareo]

And here is a view of the gunk

Oh, and I appologise for terrible pictures from my ipad

 

[Brian Legge]

Removal requires a spanner but is relatively straight forward as these lenses go. Occasionally the Canons have a bit of coating loss from these lubricants but even then they are much better after cleaning.

 

[trondareo]

Looking closely at it , it seems like most of the contamination is on the second to rear lens.

I do have a spanner, so I should be able to open it from the back. From the front, however, the two slots for a spanner are tiny.

 

[trondareo]

I was surfing the interwebs looking for more info when I came across this blog describing the dismantling of a canon 50 1.8 serenar. http://jelabs.blogspot.no/2011/04/canon-serenar-f18-50mm-ltm-lens.html

Is this the same lens?

 

[Maiku]

Your version is later black version. It is prone to fogging due to the oil Canon used to lubricate the lens.

In your case I offer this advice, if you feel you want to do it.

Remove the housing from the back. Leave the front alone! Depending on what version you have you will run into three scenarios.

1. There is a retaining ring behind the rear element holding the middle elements in place that you can remove. Use a rubber band or some like a bathtub stopper to get a good grip on it. Hold the rubber grip turn while holding the front of the lens. The middle lens element should fall out thereafter. Be careful/ be aware which way the rear AND middle lens came out (concave or convex).

2. The are two small circles where you can insert small pointed spanner wrenches to remove the retaining ring. Same procedure as #1.

3. The middle element are cemented together. In this case just give up and use the lens as is.

In most cases when you can clean the middle element this lens will fog again at some point, so you must stay on top of it.

Again there is no need to gone in from the front. Access to the middle elements is from the rear in my experience. I have taken apart about 10 of these. Cleaning these lenses is not hard, but getting access to the middle elements in most cases is hard because 7 of the 10 lenses I had were cement together!

Good luck.

 

[trondareo]

Thank you for encouragement and a usefull description!
I opened the rear ring and was able to lift of the focusing grip.
I found a brown colored shim that I left in place round the barrel for now.

The next step, i guess is to remove the rear lens.

 

[trondareo]

I found version two of the ones you described Maiku. Except there were slots and not round holes in the rear lens retaining ring. The lens came out easily. (Note to self, I placed it rear side down)
You can also see I took of the shim.

 

[trondareo]

It looks like I am stuck!
The second lens retaining ring has no place to apply a tool, and I was unable to loosen it buy hand, using a piece og plastic tubing to get a grip on it.

UPdate! It was not glued in!
With plenty of compression between the front of the lens and the retaining ring it started to move. I am finally into the next section.

 

[Maiku]

Good. Just be patient. Take your time. The one worry is that fogging has been there so long it may not be able to remove it. I hope that is not the case. Good luck!

 

[trondareo]

Thanks!
Tomorrow I am of to the local foto dealer to get lens cleaning fluid an a big dust blower.

 

[ssmc]

I hope you can get it cleaned up. I have a black 50/1.8 II Canon LTM which had some "fogging" on an inner element (otherwise almost mint!) and I had it professionally CLA'd. Unfortunately the fogged lubricant had actually corroded (?) most of the coating off that surface. It's clean now but still looks terrible and I'm told that re-coating would cost more than the lens is worth 🙁

Best of luck!

 

[Frontman]

This haze may or may not be easily removed. Sometimes cleaning fluid will work, sometimes not. If cleaning fluid doesn't do the job, you can use toothpaste with a damp cotton swab. This should get the lens clean enough to use, though there may be a bit of haze left. If you have some free hours, you can polish off the haze (and internal coating) with an eraser (on a pencil) and toothpaste. This is a tough task. Never try to use a power to to polish out the haze, this will always leave galling. I have cleaned a few dozen old Canon lenses, of all the old lenses you will find, Canon lenses are the worst when it comes to chronic haze.

 

[trondareo]

If the haze is oil based, crc electronics cleaner might work, there is some pretty strong solvents in it. But I am hesitant to use it due to getting it in the apeture blades.

 

[kuuan]

It looks like I am stuck!
The second lens retaining ring has no place to apply a tool, and I was unable to loosen it buy hand, using a piece og plastic tubing to get a grip on it.

UPdate! It was not glued in!
With plenty of compression between the front of the lens and the retaining ring it started to move. I am finally into the next section.

actually there is no need to take out that last lens element, screw off it's housing instead. See my photos, you will see the last lens still stays in place.
I have encountered two different versions: on the copy seen to the left the whole block screws out, it's the inner surface of the last glass, the one facing the aperture assembly, that will be milky and needs to be cleaned.
On the copy seen to the right only the housing of the last lens will screw off, but it will reveal two slots for a lens spanner to screw off the next block to get to the milky glass. I hope the photos explain:

the glass to clean is the one now seen on top of the turned around block seen on the lens to the left, on the one to the right one can see the slots to screw off it's block to get to it

This haze may or may not be easily removed. Sometimes cleaning fluid will work, sometimes not. If cleaning fluid doesn't do the job, you can use toothpaste with a damp cotton swab. This should get the lens clean enough to use, though there may be a bit of haze left. If you have some free hours, you can polish off the haze (and internal coating) with an eraser (on a pencil) and toothpaste. This is a tough task. Never try to use a power to to polish out the haze, this will always leave galling. I have cleaned a few dozen old Canon lenses, of all the old lenses you will find, Canon lenses are the worst when it comes to chronic haze.

I have spent quite some time trying to polish the haze off with lens cleaning fluids and with metal polishers. Glasses improved somewhat, but I have not been able to remove the haze. really. I shall try eraser and toothpaste now. Any further tips?
( luckily the haze on the one seen to the left is only very slight around the rim of the lens )

 

[John E Earley]

I was very fortunate the lens surface on my early Seranar version cleaned up very easily and is otherwise in excellent ++ condition. Unfortunately I have two 100/3.5 Canon lenses with fungus etching on the rear lens that is permanent.

[/url]DSC00557 by jacketch1@verizon.net, on Flickr[/IMG]

 

[Frontman]

"Any further tips?"

I have lately been using cerium oxide powder, which is a glass polishing agent. This works about the same as regular toothpaste, but is less messy, though your lens won't smell as nice afterwards.

The cerium oxide comes in a powder form, to use it, wet a cotton swab (pure cotton), and dip it into the powder, making a thin past. Then apply the past to the glass surface you want to polish. A dremel tool with cotton swabs cut 1 inch from the tip makes a good polishing tool. Anything stronger than a dremel tool, or bigger than a cotton swab will cause galling in the glass. The cotton swab tips must be kept damp, and changed regularly. Using an eraser with the paste will get the haze off, but as I said, it takes a looong time.

The object is to remove the lens coating, which seems to become hazy over time. On Leica lenses, the haze (and coating) comes off easily. On Nikon, Topcon, or Minolta lenses, you usually find no haze. Canon haze is really tough stuff to remove.

 

[kuuan]

...Unfortunately I have two 100/3.5 Canon lenses with fungus etching on the rear lens that is permanent.t

same here, two faulty copies of the 3.5/100. 'etching' imo is best how to describe it, and it is hard to repair

"Any further tips?"

I have lately been using cerium oxide powder, which is a glass polishing agent. This works about the same as regular toothpaste, but is less messy, though your lens won't smell as nice afterwards.

The cerium oxide comes in a powder form, to use it, wet a cotton swab (pure cotton), and dip it into the powder, making a thin past. Then apply the past to the glass surface you want to polish. A dremel tool with cotton swabs cut 1 inch from the tip makes a good polishing tool. Anything stronger than a dremel tool, or bigger than a cotton swab will cause galling in the glass. The cotton swab tips must be kept damp, and changed regularly. Using an eraser with the paste will get the haze off, but as I said, it takes a looong time.

The object is to remove the lens coating, which seems to become hazy over time. On Leica lenses, the haze (and coating) comes off easily. On Nikon, Topcon, or Minolta lenses, you usually find no haze. Canon haze is really tough stuff to remove.

thank you very much frontman. I had received the tip about the cerium oxide before, but have not tried it yet. Have spent a long time polishing by hand using various other agents, by hand because i am 'kind of on the road' most of the time and don't have any dremel tool or other machine at hand. have come to thinking however that by hand it's simply too slow of a process to make much sense.

 

[Dez]

You may have gone to a lot of unnecessary trouble in the disassembly of your lens. In my black Canon 50 f1.8 lens, it is only necessary to slacken up a grub screw in the barrel immediately in front of the aperture ring, and the entire front optical block unscrews easily. The older chrome ones require the lens optics to be removed from the mount before getting at the area. Possibly there are different versions of the black one.

This is unfortunately a very common problem with Canon lenses, in that the lubricant used on the aperture mechanism eats the coating on the element immediately behind the diaphragm. I believe the black 50 f1.8 is the worst offender. About half the time, "fog" cannot be removed.

You need to check if you really have a problem though. I have a nice Canon 50 f1.5 lens with a similar problem. After cleaning the surface, there are patches where the coating is gone. Shining a flashlight through it looks just awful. However, in actual use, there seems to be very little impact, appearing as lowered contrast. I have done some testing of my lens at various apertures vs my lovely Summilux, and there is a difference in large prints, but you have to look hard to see it. I suspect the difference between my 1.5 lens and a pristeen one would be negligible. I have thought about removing the coating (quite difficult, by the way) but I wonder if this would help or hurt the performance of the lens.

Cheers,
Dez