Canon Serenar 50mm f/1.9 Lens Clean, Lubricate, Adjust (CLA)

Canon Serenar 50mm f/1.9 clean, lubricate and adjust

Here’s a rather thorough walk-through of the disassembly, cleaning, and reassembly of a circa 1950 Canon Serenar 50mm f/1.9 lens. You can read about its history in another post.
(follow the images left to right, top to bottom)

15 thoughts on “Canon Serenar 50mm f/1.9 Lens Clean, Lubricate, Adjust (CLA)

  1. Your blog is exactly what I was looking for. I have a quite perfect Canon IV (kinda rare) from KEH – they said Excellent and they weren’t kidding..Never seen a screw mount finder as good as this one on ANY camera by any maker ! Canon IV body came without lens of which I have plenty but wanted to use a 5cm 1.9 serenar like the one you have here. Problem : focus completely stuck.

    So question. I only want to clear up the focus issue. Just do the first few steps and be done with it ?
    thx mike


    1. Hi Mike,

      You don’t have to disassemble everything like I did. Remove the three screws holding the depth of field indicator ring/helicoid/m39 thread mount. Then skip a bunch of steps and just go after the knurled focus ring. I think you can unscrew it and clean out that section without removing other parts.

      If you’re going into that section and end up having to disassemble more, then I’d just clean up everything. The aperture will probably work a lot better. Once I cleaned mine it moved very nicely, with only a light touch. Just be careful with all those tiny screws. Keep them next to their associated parts or label them.


      1. Thanks ! Will give it a try. Actually I have other ‘perfect’ serenar 5cm lenses incl a 5cm /f2 but the one that isn’t quite right gets the attention. mike


  2. I have this Canon Serenar 50mm f1.9 screw mount lens. The glass looks very good. The f stop adjustment works well and the blades open and close nicely. The problem is the focusing ring is very stiff, it moves but it’s a struggle. The ring that screws into the feet marked base I think is cross threaded, at least I can’t get it to screw down evenly. It’s a nice lens and does take good photos but I’d like to repair it if possible. My email is and I’m in the Washington DC area. Can you work on it? All the best!


    1. Hi Michael,

      I apologize for not responding earlier. I don’t check WordPress very often and I’ve been busy with other things.

      Unfortunately I don’t have the time to work on lenses. I’m either working for a living or working on video lately. It’s photography, but with more frames!

      I suggest you dig around on YouTube to find some people who do lens repairs. I’m sure there are many who would be willing and able to work on your lens.

      Good luck!


  3. Thanks so much for this – very helpful when doing mine just now. I’m no stranger to this kinda of work, and reassembling aperture blades, but man, THESE blades were extremely frustrating to get back together! So many. So tiny!


  4. Hi Mark, can you reply to the method you used to remove the collapsing ring stop? I know that you state it unscrews, but how did you actually get a grip on it and unscrew it? A reply is much appreciated.


  5. Hi Mark, I have the collapsing ring section soaking overnight in a product that is designed to penetrate and unfreeze stubborn metal parts. I’ll try the rubber coated gloves when I attempt to loosen that stubborn collapsing ring.


  6. Hi Mark,
    I successfully removed the collapsing ring after soaking it overnight in a penetrating catalyst product. Both the focusing and aperature turn very nicely. I only need to clean the rear element pieces of glass. If that is all I wish to do, would I simply remove that tiny setscrew in the middle of the barrel to separate the rear focusing section from the front section? Thanks for your reply.



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