Disassembly – Fujinon XF 35mm F1.4 R lens – broken focus

This broken Fuji XF 35mm F1.4 lens sample got purchased from eBay. It was listed as “for parts” and mentioned that camera is often asking to restart with this lens. I decided to explore lens and see if it can be repaired, or I just use it for manual conversion.

Lens worked and focusing on my X-T30 camera but I noticed that lens core is heavily tilting when focusing – about 5-10 degrees. I focused lens to minimal distance then disconnected from turned on camera to keep focus in that mode. I was able to freely tilt lens core in one direction which indicated that some guiding mechanics is broken inside. Shaking lens unveiled some noise like small part or bolt is moving inside.

Disassembly and repair

You can check Fuji XF 35mm F1.4 disassembly steps for more details of typical disassembly process for this lens. This time broken lens required few extra steps:

  1. Unscrew two black bolts blocking inner focus ring rotation.
  2. Remove black metal ring plate from the focus ring front, then accurately remove felt strip from inner circle.
  3. Rotate focus ring to make lens core move out, then pull lens core out.

Now the problem is clearly visible. Plastic part holding metal pin got broken most likely from frontal hit to the lens. Pin felt out and lens core didn’t keep its position, which resulted to wrong focusing.

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I’ve cleaned surfaces from the grease and used strong glue gel to connect plastic part (fortunately it was still inside). After that I’ve added more glue and secured metal pin inside.

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After a minute I’ve removed glue extras and accurately polished plastic bar sides to make them flat again, it required fine grinding of plastic as well because breakage deformed part of plastic side. Finally I’ve added some grease on top.

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NOTE: Insert lens core back and rotate focus ring few times to make sure core is moving easily. Otherwise extract the core and polish the pin area plastic and add grease again.

After assembly this Fuji XF 35mm F1.4 works perfect. Lens core keeps proper position when focusing. So looks like I’ll just keep the lens in regular electronic mode and will look for another broken options for conversion.

Conclusions

Fuji XF 35mm F1.4 lens can be significantly damaged by frontal hit impact to the side of extended lens core, e.g. when camera falls on the ground with lens facing down, or hitting some object while carrying. That plastic area holding guiding metal pin is only 1.5mm thick. Fortunately it is possible to fix this mechanical issue and bring Fujinon XF 35mm F1.4 lens back to life.

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10 comments

  1. I have fuji XF 35mm f1.4 lens.
    However, it feels like something is out of focus.
    Just a little bit.
    So I tried to break it down following this article, but there was no problem.
    What’s the problem?

    Liked by 1 person

    • It is good that you see no physical problem, then logical investigation of autofocusing is required. Focus can be out for many reasons, and usually I’m trying to systematically test them to narrow down. Is it always out of focus to same direction form target (back or front)? Is the focus offset of random size, or it’s always “a bit” no matter the focusing distance to the target?
      Other things may also influence. There is a little mechanical play of XF 35mm F1.4 focusing core, and I noticed that sometimes after autofocusing and locking focus by rear button (AF-L), when I half-press the shutter, Fuji camera makes focusing core quickly shake (in spite focus is already locked) – I never find the reason why Fuji doing that, but it often shifts the focus a bit. Another focus shift may happen when you actually move camera a bit after focusing, so try to do it from tripod or from table and check. I’ll be glad to answer more questions.

      Like

      • I tried it automatically and manually adjusted the focus.
        But it still doesn’t feel right.

        I think it’s more of a focus.
        It seems to be a matter of resolution.

        No matter how I look at it, there is no problem with the appearance.

        + Thank you. I didn’t know there would be comments.
        This is South Korea.

        Like

        • If you think it is resolution, then try closing aperture, and see if resolution improves.
          I like MTF test on opticallimits: https://www.opticallimits.com/fuji_x/746-fuji35f14?start=1
          That chart is showing that best resolution in center can be obtained at F2.8 – F4 range, which is expected for fast lens.
          Also, Fuji didn’t make XF 35mm F1.4 to have extremely detailed resolution, they try to balance resolution and natural look. Probably, if you just keep shooting with it and learn more how it behaves, over time you may start to like how the resolution behaves.
          Also, feel free to email me your pictures, I’ll be glad to comment them if there is any technical out of focus, or it is expected behavior of XF 35mm F1.4 lens. yukosteel@gmail.com

          Like

              • Jones, that is impressive result of your accurate investigation and repair of Fujinon XF 35mm F1.4, congratulations! I’m glad that article helped you to deal with lens disassembly. And thank you very much for sharing what you discovered and repaired.
                I’m disclosing that for other readers. You decided to inspect lens optics and realized that one of inner glass elements was shifted in the front lens module frame. After you corrected glass element position, lens started to work much better.
                Here is the relevant article of resolution degradation and repair of 7Artisans 50mm F1.8 lens: https://yukosteel.wordpress.com/2018/06/30/bad-lens-or-optical-alignment-issue/
                It’s nice to see that you discovered that problem by your own and also repaired it – great job done!

                Like

                • In a way, it was a very simple problem.
                  The lens decomposition was so scary.
                  But you did it with courage.

                  Thank you, yukosteel 😀

                  Like

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