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How to Dismantle and Clean a 50mm Lens

Lenses for Pentax

How to Dismantle and Clean a 50mm Lens

Posted by: Kit. on Tue Dec 13, 2011 16:49   (8219 Reads)
 
Step by step instructions, with pictures, on how to dismantle and clean a 50mm lens....
 
 
Here is the Pentax 50mm F1.7 SMC-M, found by thoramay in a charity shop.





And here is the stuff we will use to clean it.




First job, is to remove the finishing ring, from the front of the lens.




This is done by cutting a double sided sticky pad into 4 pieces, and sticking them to the ring, as in the above picture.

We now place an M42 rear lens cap on the pads and press down firmly.




Unscrew the ring, in an anti-clockwise direction.




Now we can remove the filter threaded front tube. This is done by removing the three little screws, highlighted with white paint, in the picture above.





With the front tube removed, we have easy access to the front element retaining ring.



The element is held in place by the inner ring (marked white) in the picture, above.
The correct tool for removing these rings, is a lens spanner. I do not have one. Fortunately, they were not very tight, and I was able to undo them with my fingernails. The rings undo anti-clockwise.



With the ring removed, the front element will drop out.

We can now remove the second element assembly. If the retaining ring is tight and you do not have a lens spanner, a steel rule placed across the ring and located in the slots, can be used to loosen the ring. - But only if it does not foul the lens element!




The second and third element assembly also unscrews anti-clockwise.



Below, we see the second and third elements seperated



With the front group removed, we can turn our attention to the rear group.



Remove the five mount retaining screws.



DO NOT REMOVE THE APERTURE RING! - It is not necessary and doing so risks losing the tiny spring and ball baring within.



With the bayonet mount removed, we can now simply unscrew the rear group assembly by hand... Again, anti-clockwise.



Here are the two rear elements separated



Ideally, the rear element should be removed from it's housing, but the retaining ring was very tight and I could not undo it. Not really a problem, as we can clean it as it is.

Now that we have removed all of the glass from the barrel, We can set to cleaning.
Dip a cotton bud into the vinegar and swab each element gently. Leave the vinegar on the glass for a few minutes, to do it's work of killing the fungus.



After the vinegar treatment, wash the elements in soapy water. I used washing up liquid. Wash until 'squeaky' clean, then rinse well in clean running water to remove all traces of the detergent.
Dry immediately with a soft, lint free cloth.


Here we see the now cleaned elements laid out in order.



The lens is now cured of it's infection and can be reassembled.
Reassembly is of course, the reverse of the method we used for the strip down.





Here is our patient. - Reassembled this evening and fully restored to health.


 
 
 
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All 10 Comments

How to Dismantle and Clean a 50mm Lens   -   Leave a Comment
Re: How to Dismantle and Clean a 50mm Lens   -   See entire comment I want to dismantle an A 50mm lens to remove the glass. Do you know if it would be the same process as dismantling the M or is it likely to be a bit m ...  more
Re: How to Dismantle and Clean a 50mm Lens   -   See entire comment The A lenses are pretty much identical to the M ones, only thing is they have a plastic finishing ring which may be harder to unscrew. The two element ...  more
Re: How to Dismantle and Clean a 50mm Lens That's great DM,
Thanks once again - I dunno what I'd do without you. :D
Re: How to Dismantle and Clean a 50mm Lens   -   See entire comment
- Charlotte
I want to dismantle an A 50mm lens to remove the glass.
I think I know what you're up to! :D  more
Re: How to Dismantle and Clean a 50mm Lens   -   See entire comment I expect you're probably right as well DS.

I'm not sure whether or not it's going to work though - we'll see. At least with the older lenses I can ...  more
Re: How to Dismantle and Clean a 50mm Lens Some info and useful links on this page....

http://www.pentaxuser.co.uk/forum/topic/smc-pentax-a-1-2-50mm-39483
Re: How to Dismantle and Clean a 50mm Lens   -   See entire comment Just to update anyone who might have been interested.

The A50mm 1.7 is a thing of beauty and I can't bring myself to do anything to it apart from u ...  more
Re: How to Dismantle and Clean a 50mm Lens   -   See entire comment The A50 f/1.7 is one of the best standard lenses ever made. I've actually got 3 of them
2 came with Super A bodies that I bought.

Unfortunately th ...  more
Re: How to Dismantle and Clean a 50mm Lens Maybe keep your eyes open for a cheap 50/1.7 or 50/2 with a damaged front element?
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