Disassembly - Voigtlander 35mm F0.9 Nokton Aspherical Fuji X mount lens

 In this article I'm partially disassembling latest ultra-fast aperture Voigtlander 35mm F0.9 Nokton Aspherical Fuji X mount lens (optical performance is briefly reviewed here). The goal is to explore way to fine-tune infinity focus hard stop point  , analyze build and estimate complexity of potential maintenance of glass surface.

 

Front area disassembly

Voigtlander 35mm F0.9 front nameplate is factory glued in front filter thread. Few drops of acetone need to be radially applied first to dissolve glue. Later I'm using three Loctite putty strips attached to standard Sony E-mount lens rear cap, pressing firm to grab Voigtlander nameplate and unscrewing it CCW from filter thread. Set aperture ring to F5.6, focus to 0.35m and use rubber strap to only grab front lens area above focus ring while unscrewing nameplate, to not stress focusing helicoid guiders. Below is unscrewed and cleaned nameplate.

Next step is to unscrew three silver bolts marked below. WARNING - do not unscrew any other bolts because it may ruin precise factory optical alignment of front glass elements.

Remove the front ring. It's impressive to see how thick and durable it is to be able to absorb potential impact from lens hood hits. Cosina is using lighter build for Fuji X mount lenses, and unlike Leica M mount lenses this ring is not made of heavy brass but same lightweight metal alloy is used everywhere.

Locate the aperture click-stop metal ball and put it in safe place during disassembly. Its original location in spring loaded tunnel is marked below.

Remove the aperture ring. Here is one more look at the top side of aperture ring with marked location for ball.

Inner side of aperture ring has aperture transmission made of thick brass plate.

Aperture transmission is grabbing brass plate slider controlling lens aperture opening.

Front lens frame has special cut groove for aperture transmission.

I see bright metal shim between front optical frames. Looks like its location and thickness is precisely selected during factory assembly. I'd not recommend open lens further even for minor cleaning, unless there is something bad happening with glass surface. Realigning precise centering would be quite challenging without special equipment.

Here's one more interesting engineering touch of lens build - white plastic cylinder is inserted into dedicated socket to increase smooth movement of large aperture ring.

Rear area disassembly

Voigtlander 35mm F0.9 Nokton lens has electronic contacts so mount area opening requires extra steps to release contacts frame. First I'm unscrewing four silver and three black bolts. All bolts are extra secured with glue and initial radial torque using pliers holding screwdriver will help to break glue without damaging bolt head.

Extract black metal ring around rear glass frame, then unscrew two bolts holding contacts plastic frame. 

Gently lift up contacts frame from mount ring and then lift up and shift the mount ring. Then accurately direct contacts frame through mount ring opening and disconnect mount ring.

Note, there is a set of metal calibrating shims under the mount ring.

Next step is to unscrew four silver bolts and detach rear shell ring with DOF scale. It is exposing access to main electronic board of Voigtlander lens.

There is a pair of double-contacts tracking radial position of manual focus ring.

Manual focus ring rotation stop point is nicely dampened by using whitevplastic cylinder attached to focus ring. It is meeting with metal bar at hard stop. Cosina engineers designed this lens to slightly overpass infinity focus point, perhaps to address potential variations of Fuji X cameras mounts thickness.

I decided to craft and add micro brace made of brass to stop focus ring at exact infinity focus location.

It's designed to be easily detachable, but also to hold its location firm.

Focusing is now stopping slightly earlier at exact spot I measured earlier with Fuji X-E2s and X-T5 when focusing on distant star at F0.9 aperture.

For further disassembly the electronic board have to be removed. First you need to accurately lift up black locking plate on two micro sockets and release two narrow ribbon cables.

Then unscrew three black bolts and detach electronic board.

Now you can unscrew set of four silver bolts and disconnect metal ring holding focusing distance board.

It opens access to contacts of focusing distance.

The board of focusing distance measurement has large radial length for precise measurement.

When focus ring is slightly passing infinity mark there is free access to bolts holding thick and durable brass helicoid guiders.

Two of them maked with green arrows are directed toward front lens and supporting focusing. Two guiders marked with red arrows are directed toward rear lens and supporting FLE movement.

Further disassembly may affect calibration of FLE and focus movement, so I'm stopping at this point ang assembling lens back in reverse order.

Few notes for proper assembly - make sure ribbon cables slide into board sockets firm before locking sockets, also watch the proper location of aperture ball and transmission during assembling front area.

Conclusions

I'm not surprised to see that Voigtlander 35mm F0.9 Nokton Aspherical lens has very advanced build with extremely high machining quality of all parts. It is quite complex lens optically and mechanically and its proper maintenance and even basic cleaning requires highly skilled actions. I would not recommend to perform any DIY cleaning and repair even if you have good experience working with lenses - it's one of that more rare cases when I'd personally ship the lens to service center instead of attempting to repair it myself.

The build is very robust and solid, lots of large durable bolts are used to hold precisely machined parts together, and inner frame is all crafted from thick metal. Lots of brass is used for helicoid guiders including FLE mechanics, and aperture transmission is beautifully crafted too.

Personally I think the weakest spot of this lens is its electronics which may get potentially damaged or broken over decades of intense use, but that will not affect mechanical and optical performance of Voigtlander Nokton 35mm F0.9 in any way, so in general it's very reliable tool that can serve for generations if properly maintained.

More pictures taken at F0.9 with Fuji X-E2s