Full disassembly: Fujifilm XF 50–140mm f/2.8 lens

This is a full disassembly/teardown of the Fujinon XF 50–140mm F2.8 R LM OIS WR lens. Hoping that you will never need it. Because there are few online resources available to guide the disassembly or repair of this lens (and Fuji lenses in general) I decided to contribute some documentation in the hope this might help others who might (god forbid) need it sometime. I did this so that you don’t have to- don’t try this at home and if your lens is broken bring it to an official repair store.

I wish the reason for being able to do this teardown was more exciting, but it is a rather sad story that involves me diving to the bottom of a lake during a sailing trip to recover it. Something that warranty explicitly does not cover, it is safe to say that this specimen has been totaled and will become a beautiful paperweight on my desk. But let’s not dwell on that.

Overall summary: this is a well put together lens which is challenging but is assemblable for a semi-experienced amateur. Two aspects make the teardown especially annoying: (1) some ‘invasive’ steps are required which involve carving out hardened glue, and (2) a very unintuitive step of removing the aperture ring introduces a high risk of ripping the aperture flex cables. 🤐

Disassembly layout of the Fujinon XF 50–140mm.

Optical groups on the right from top to bottom, on the left side of the photo:
1: front lens group
2: zoom lens group
3: focus lens group with double linear motor
4: optical stabilising lens group
5: rear lens group.

Other recognisable elements:
- top row, second from left: aperture diaphragma
- second row, second from right: aperture dial ring
- top row, rightmost: lens barrel with focus ring and zoom ring
- rightmost, second from the bottom: tripod collar mount
- bottom row, third from right: rear bayonet mount
- bottom row, second from left: rubber zoom ring cover

General introduction

Disassembling from the front part of the lens gives access to (1) the front optical element, (2) the zoom optical group, and finally (3) the focusing optical group.

Disassembling from the rear will allow access to: (1) the X-mount rear bayonet including circuit board with connectors for all the onboard electronics, (2) the rear lens element, (3) the aperture dial and sensor, (4) the OIS optical stabilisation lens element group, and finally (5) the aperture diaphragma.

With this lens only the zoom is operated manually. The aperture, zoom, and (obviously) the optical stabilisation are all fly-by-wire which means that your manual input is converted to electronic signals and then translated by actuators into mechanical movement inside the lens body.

I will first post a detailed guide of the front disassembly, which I needed to do because there was lake water residue stuck to all the glass. And I find it very important that my new paperweight be as pretty as it can be. At a later stage (when i find a replacement for the broken diaphragma module and the aperture dial flex cable) I will append a guide on the disassembly of the rear elements.

The two casualties of a sailing trip after a week in a bag of rice.

Lens disassembly I: front lens elements

This part covers the disassembly of the following parts of the lens:
- filter thread and lens cap mount
- front optical element
- zoom optical element
- focus group element with linear actuators

The Hoya uv-filter took a hit and shattered but this probably spared the rest of the lens. So definitely always put a filter on your lens.

The first step was to remove the Hoya uv-filter which was shattered hitting the deck before dropping into the lake. I used a a metal hacksaw to carefully weaken the rim by cutting through the thickest bits at two places opposite each other which allowed me to easily bend open the rest of the filter without further damaging the lens.

The next step is to remove the ‘makeup ring’ with text as better described over here. Four places around the ring have adhesive tape securing the ring, for my lens there was one around ‘XF’ and the opposite side, and one around ‘WR’ and the opposite side. Slowly push the ring away from the center and you should feel the adhesive let go, move on to the other adhesive parts, and when all are taken care of the ring will pop off smoothly. Take care not to bend the ring because it will become ugly. Underneath is a plastic base and a spacer ring, which can be easilty turned out without damaging it (I used a caliper to turn it). Righty tighty, lefty loosey.

Removing the ‘makeup ring’ and unscrewing its plastic base reveals the four screws that hold the filter thread and lens hood mount in place.

Underneath the makeup ring we find that the metal filter thread ring/lens hood mount is secured with four screws. Remove and continue. The water inside the lens hadn’t even dried after a week in rice! The lens group even had a puddle in it that you could shake around and see move.

The front lens element is hard-glued into its base. There is glue on the ‘screw-fins’ which hold the springs in place and on the ‘floating-fins’.

Underneath the filter thread ring we find the mount of the front lens element. It is glued in place with hard (two-component?) adhesive that apparently is resistant to heat and alcohol. This is the first invasive step of the teardown. Now ‘carve’ out the glue surrounding the screw holes to free the fins. The screws can now be removed, but beware that they hold the springs that hold this lens element in place.

When the screw-fins are free from glue, the remaining glue holds the ‘floating’ fins in place. These fins were clearly glued in place by the engineers that made this lens. Knowing how tack sharp this lens is, it is probably calibrated extremely precisely to be in this position, and if you ruin the glue your lens will never again be in the correct position. If you want to put it back together, make sure you only cut away the connection between the glue and the element. Leave as much glue as possible on these fins because if you remove it all you will never have the element in the right position anymore.

The front lens element, before and after drying and cleaning. The front part of the zoom group can be unscrewed but this isn’t recommended unless you want to clean out any lake gunk that ended up in there.

Underneath the rubber zoom cover, six screws in white spacers around the lens barrel hold the zoom group and the focus group in place.

Now to remove the zoom group and -it took me a while to find this step- slip the rubber zoom ring cover off. Thankfully no adhesives and the next few steps are non-invasive.

The three screws and spacers on the frontside must be taken off (leave the back three on for now) to loosen the focus group. Make sure you hold the barrel horizontal otherwise the elements will fall out. Take care not to drop them in the barrel because the focus actuators hold strong neodymium magnets which will make your life miserable trying to find them back if you drop them in. With the screws loose the focus group can be carefully lifted out.

Three white spacers hold the focus group in place. The lake residue is yet to be cleaned out of the stabiliser group!

The focus group can just as easily be removed from the barrel by carefully removing the three screws and spacers whilst holding the barrel horizontally. In this picture the aperture ring can be seen, as well as some lake gunk stuck in the stabiliser group. Beware that the focus group has a flex cable sticking through the barrel that is secured by adhesive along the way. Don’t tug on it without removing the adhesive first or you will regret it.

The focus group with the three neodymium linear actuators that allow for the blazing fast AF.

Disassembly II: rear lens elements

~Work in progress, check this out if you can’t wait~
This part covers the disassembly of the following parts of the lens:
- the X-mount rear bayonet including circuit board
- the rear lens element
- the aperture dial and sensor
- the OIS optical stabilisation lens element group
- the aperture diaphragma.