Disassembly – Viltrox 85mm F1.8 lens (Fuji X mount)

Today I found time for explorative disassembly of Viltrox 85mm F1.8 lens rear area to evaluate build quality. In this article I’m showing Viltrox 85mm F1.8 electronics and access to aperture chamber.

Disassembly steps

First step of disassembly is quite traditional – unscrewing four Torx bolts of the lens mount. I used T5 screwdriver on my sample.

Bolts are quite long and thick to properly secure Viltrox 85mm F1.8 lens weight (of about 1.5 lbs).


Next step is important – locate tiny silver bolt on the side of mount ring and loosen it by making at least 2 full turn (otherwise electronic contacts remain locked). After that unscrew three small black bolts around rear lens. I’d recommend to cover rear glass with protective film to avoid accidental scratches.


Accurately take out inner black ring. Nice – it is made of metal.


Now slightly elevate mount ring (be careful, there is ribbon cable under it, don’t stress it), then release electronic contacts and remove mount ring.

Viltrox are making very good quality adapters so it’s not surprise to see that Viltrox 85mm F1.8 lens has properly machined brass mount ring covered with chrome.



Now interesting part – there are four huge cylindrical calibrating shims made of brass. Remove them first, then detach electronic socket  in the bottom board area and unscrew three black bolts marked with red arrows.




Note – there are three small metal shims under the electronic bolts, make sure you put them back during assembly.



Now unscrew three black bolts in the inner area marked with red arrows. I also unscrewed another larger three, but DO NOT do that, it is loosening rotation of rear lens body with “85F1.8” sign, which may damage lens ribbon cable if inaccurately rotated.



Now you can accurately pull out whole rear lens module. I realized that upper securing ring above rear element is also additionally secured with glue on factory. This is multi-elements lens with complex optical formula, so DO NOT disassembly this optical module.


There is rectangular socket on the inner side of rear lens module – it fits position of electronic board of aperture control inside, so fit it properly during assembly.

Now you have access to aperture chamber, blades and inner glass surfaces for potential cleaning if ever needed. Looks like there is also electronic drive which controls aperture.


I also noticed few long metal poles near the lens frame walls, looks like they are supporting internal focusing movement.


At this point I’ve stopped disassembly, because it’s fully functional lens and further explorations may cause unnecessary failures, so I accurately assembled everything back in a reverse order. Don’t forget to connect electronic board cable with extra caution.

I’ve realized that Viltrox engineers follow very high quality standards. Everything inside lens looks very clean and accurately done. All bolts are secured very tight and perfectly centered. It was very interesting to explore the build and I can compare it with disassembling Fujinon XF 56mm F1.2. It is nice to see that lens mount is secured to metal inner frame which also looks thick and very durable. Looks like only very little plastic is used for aperture module frame, but everything else is precisely machined from metal. Great job done Viltrox!

Firmware updating

I also searched for details on micro-USB cable on Viltrox 85mm F1.8 lens, and found related Viltrox site page for Firmware Upgrade. Everything looks intuitive and they also have very clear Upgrade Guide which you can only find if check previous V1.01 version for Fuji X.  I checked my sample and realized that it already has latest firmware version.





It is relatively easy to disassemble Viltrox 85mm F1.8 rear lens area if you have proper tools and experience. Looks like it’s better to avoid using Viltrox 85mm in a rainy weather because there is a risk that water may cause shortcut of electronic board. From the other side looks like that lens internal focusing does not require external air ventilation, so this Viltrox 85mm should not collect external dust during focusing which is great. The parts and frame construction look high end with very good precision and very accurate factory assembly. Looks like Viltrox mini-certificate of QA included in package really means that this sample was properly inspected, because I didn’t find any visual defects even during the partial disassembly. Now it’s time to run few weeks of extensive use of the lens and evaluate overall performance in different situations.



    • You are right, it’s best practice to mark and put each shim and even bolt to exactly same place during assembly. Thanks for bringing this point.

      Each master is using own technique modified to personal work style. Typically I’m locating removed parts left-to-right in a row, or when disassembly is minor – near the lens in a pattern regarding lens orientation. In this case I’ve positioned shims on the surface in order for assembly locations of mount bolts, so they came to same place.

      Liked by 1 person

  1. Hello Yuko, I think Viltrox and Zhongyi need your intelligence now 😛

    Recently, Viltrox issued a warning to its users not to use the lenses on Fujifilm X-Pro3 since it can damage the lens release button. Why? Because Fujifilm reduced the distance between the lens release button and the lens mount. So lenses with a large diameter bottom will scratch (and conflict) with the release button.

    Here are some examples:
    Mitakon -> https://www.dpreview.com/forums/post/63985451
    Viltrox -> https://www.indiatoday.in/technology/news/story/viltrox-lenses-can-damage-fuji-x-pro3-camera-model-1678117-2020-05-14

    What’s your thoughts? Do you think you can come up with a solution to fix the conflict without harming either the camera or the lens?

    Thank you so much!

    Liked by 1 person

    • Thank you! : ) I like interesting questions like this.

      Yes, it is possible to accurately grind the Viltrox mount ring edge area to eliminate conflict with X-Pro3.
      It’s quite trivial operation in this case because there are no electronic or mechanical components that can be affected by removing thin layer of metal from the mount ring. Because it’s only edge area it will not also affect optical alignment.
      If I had X-Pro3 and very much willing to use Viltrox 23mm/33mm on it I’d just do that. If ring is aluminum, no extra actions required, but if it’s brass inside, I’d then paint grinded mount ring area with special Molotow marker called “Liquid Chrome”. As a result lens would be fully compatible with any other Fuji X-Pro3, and mount ring would look still beautiful.

      Liked by 1 person

      • Brilliant! Thank you so much Yuko.

        I think I might take my Mitakon to a metalsmith to do this for me since I don’t have the required tools. I might also paint it all in black since I’m interested in black X-Pro3 and the silver ring bothers me haha.

        I will share the link to your reply on the DPReview thread if you don’t mind. Cheers!


  2. Hey, Yukosteel, good evening!
    I have a Viltrox XF 85mm, but the mark ii, and I have a big problem, and wanted to ask if you have seen something like that or can shine some light on me:
    Some time ago I bought those lenses and it worked just fine. After 4 months of little to no use of it (I took it around just once, and took something close to 100 pics), I returned her to the body and the camera system just crashes and is stuck on a loop of turning on and off.
    I think that is not a firmware problem, as it worked just fine before.

    Do you have any idea about that?

    I think there is a problem with the focus motor or even the conectors.

    Could it be fixed somehow?

    Sorry to bother you with this man. Cheers!


    • Hi Fernando, sorry to hear you’re experiencing troubles with Viltrox 85mm lens. One of my friend has version II but is not available these days, so can’t look at it directly.
      I agree with your assumption regarding lens contacts. What I’d try to do is checking that lens is attached at exact position where all contacts are connected, maybe there is a small radial shift of contacts. Another thing to check is trying to see if there are any settings you changed over time in camera and maybe some settings is not compatible with lens firmware, though it’s very unlikely.
      What I’d do to experiment is to power off camera, then attach lens, press lens release button, and rotate it in mount to few degrees CCW or CW, then turn on camera and see how different is whole behavior.
      Could you please also send the picture of the contacts area of the lens. I can use that picture to compare it with another Viltrox mount lens I have and see if there is any contacts shift.



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