cleaninng the glass of a canon ltm lens

[michael_hassoun3]

Hi all

 

I need to clean the internal surfaces of a canon 50mm 1.8 which else than a

heavy haze, looks great.

dismanteling the focussing mount is done.

 

Any suggestions about opening the optics?

which end should be the first to be opened?

any specific way to open and more important, to place back the lenses?

what should I use for the cleaning?

 

Thanks!

[michael_hassoun3]

John are you there :-)) ?

[steve_levine]

""what should I use for the cleaning""

 

 

Someone that knows what they are doing.

[john_shriver]

Best way is to pay DAG about $75 to do it.

 

You don't need to dismantle the focusing mount. Just remove the lens block from it by unscrewing the outer slotted spanner ring at the rear. Pull the lens block, don't lose the important spacer shim.

 

You will see that there are two lens assemblies screwed into the aperture assembly. Make scribe marks showing how tight each is screwed in. Then unscrew them one at a time, and clean the surface facing the diaphragm. Screw them back in so the scribe marks match.

 

If there is haze on surfaces inside those blocks, I'd really leave it to a pro, since you have to use a spanner wrench in tight quarters, really close to the glass. Also, reassembly of these is far more critical, you need to check the centering.

 

Unlike a Leica lens of the same vintage, the same cleaning techniques that work on the outer elements work on the inner elements. No soft coatings here. I use Residual Oil Remover lens cleaner, and facial tissue or lens tissue.

[michael_hassoun3]

Thanks!

Don has all my critical jobs. He is currently working on my "new" summitar, summicron and a IIIf.

 

I 'm doing this for fun... on items I won't mourn if I mess totally.

 

I think I got it but...how do I "check centering" ???

[michael_hassoun3]

"I think I got it ..."

 

Not quite right. How do I unscrew these blocks?

 

Thanks again

[stephen_w.]

The elements should be self centering. Do manufacturers actually place shims on the sides or bottoms of each individual element and for each lens? They should fit in their metal/plastic mounts perfectly. Of course, this is just an educated guess on my part and for the sake of discussion. 8*)

[leicaglow]

Does the infamous DAG have a website?

[hxt]

I just had Horst Wentzel clean a lens for me... a canon 50 1.4. he does excellent work, and cheap! I think he charged me $40... he is in Vancouver B.C. look him up<div></div>

[elmarfudd]

Don Goldberg's site is dagcamera.com . He's very responsive, despite a large workload.

[winfried_buechsenschuetz1]

"The elements should be self centering. Do manufacturers actually place shims on the sides or bottoms of each individual element and for each lens? They should fit in their metal/plastic mounts perfectly. Of course, this is just an educated guess on my part and for the sake of discussion."

 

...but it is completely correct. Lens elements are centered after grinding the surface. Probably cemented elements are centered after cementing them. Usually it is assumed that the optical axes of all lens elements are in the same position (with acceptable tolerances).

 

There are some Zeiss Jena lenses which have excentrical rings to center the rear elements.

 

However, I would not recommend doing a lens cleaning job at home. Whatever you do - after reassembly there will be much more dust inside than before.

 

Haze on lens surfaces (whatever it comes from) in many cases disappears when cleaning with a microfibre tissue.

 

Check whether your lens has oily aperture blades. If so, the oil should be removed since it might evaporate haze in the future.

[john_shriver]

The tool needed is a lens spanner. If you don't have one, you need one to do it right. Or something very rigid that will engage the two notches, apply torque, and not slip out and scratch everything to death.

 

I don't know if any of Canon's lenses were centered by "try and try again" putting the elements into the aluminum blocks. (Japan was the leaders in "statistical quality control" and building things to tolerance, rather than try and fit, which is what Leica was still doing in the 1950's.) But opening one up is just more risk than unscrewing it from the lens.

 

But there's very little chance that there's haze inside the blocks, it's normally next to the diaphragm.