Disassembly - Voigtlander 50mm F1.2 Nokton Leica M mount lens

 This article describes how to partially disassemble one of the newest fast aperture Voigtlander 50mm F1.2 Nokton lens in Leica M mount. While most of older classic lenses disassembly steps often start from the lens mount area - many lenses of newer Voigtlander line need to be opened from the front.

Disclaimer

For this and some other articles I'm going to add non-affiliated links to my favorite lenses shop in US - well known and reputable official distributer of Voigtlander lenses - CameraQuest. I'm not getting any income from links, only posting because I learned a lot about Voigtlanders from their portal, and purchased few lenses from CameraQuest with excellent support and best experience. I also like that they quite often selling returned lightly used Voigtlander lenses for significant discount.

Disassembly steps

First step is to unscrew the front nameplate ring. I'm using few drops of acetone applied to outer border of front nameplate to partially dissolve factory glue. Then I'm cutting three strips of very strong double-side 3M adhesive foam and attaching them to the edges of standard sized Leica M mount rear cap. This cap has smaller diameter than Voigtlander mount cap, and perfectly fits the size of lens front nameplate. Most important is that cap is hollow inside, so nothing is touching front lens glass.

NOTE: it's important to grab as large ring area as possible, from the other side attaching adhesive foam to nameplate lettering may remove white paint. Usually I'm repainting letters using made in Japan oil based white paint marker if needed. Though with larger nameplate rings like in this Voigtlander 50mm F1.2 lens it is enough to add adhesive foam to three areas that has no lettering.

Firm press and strong CCW movement should release front nameplate and you can unscrew it completely.

I'm accurately removing adhesive foam. The ring is thick and durable enough to not get bent.

Next step is to unscrew three black bolts holding chromed ring with hood mount petals. They are secured with glue, so initial CCW torque is required while pressing screwdriver toward bolt head.

After removing front chromed ring you will get access to 12 bolts positioned at different depts. Many of that bolts are additionally secured with large amount of external glue. Fortunately for further disassembly you only need to unscrew three silver bolts which sit most deep and marked on picture below.

NOTE: Aperture ring need to be set to F1.2 position, otherwise access to marked bolt heads will be partially blocked and they can not be fully unscrewed. At F1.2 aperture value access tunnel to all three bolts should be round and clear.

After unscrewing 3 bolts, grab aperture ring and accurately pull out front lens section. It may come out together with thin brass calibration shim rings. It is important to memorize their radial position, and fit holes for bolts while assembling lens. These shims are calibrating real infinity focusing of the lens.

Now when whole optical frame is separated from focusing frame, it is possible to further disassemble every part separately. My goal today is to clean large dust particle from optical path, so I'm not disassembling focus frame. However if you need to - next step would be to remove calibration shims and unscrew three black bolts visible on the inner side of focusing ring.

Here's the look through optical path front the front, and you can see three bright tunnels where bolts connect optical module to the focusing frame.

Side view to optical frame shows more interesting details. There is aperture transmission made of brass and secured with two black bolts. In the middle there is also a thin brass strip - most a set of shims to precisely calibrate lens focal length. It looks to me that cylinder right next to thin brass circle can be unscrewed CCW. I'm first marking position of small squire detents to fit radial position back to original place during assembly. 

Then I'm using soft rubber strap wrapped around rear optical module and accurately unscrewing it in CCW direction. As you can see there is set of thin brass calibrating rings, be careful not to bend or touch them with fingers, brass is oxidizing easy over time keeping fingerprints forever.

At this point I'm using air Rocket Blower while facing front optical frame up, to blow out large dust particle from the aperture chamber, which is bringing lens back to factory-clean shape. After that I'm screwing in rear optical module making sure pencil marks on both cylinder fit perfect, which sets precise calibration back to original.

Finally I'm following disassembly steps to put lens back together. I purchased this Voigtlander 50mm F1.2 Nokton lens copy used and it was definitely not laying in shelf but had some good shooting time. There are numerous wear on anodizing surface of mount and aperture ring texture edges. I'll later darken that areas using metal blackening acid, that works quite well on Voigtlander lenses. 

Conclusions

Like with 40mm F1.2 model, this Voigtlander 50mm F1.2 Nokton lens has more complex mechanics due to larger amount of glass. Optical and focusing frames are built like a tank and large amount of brass used where it's increasing frame durability. Cosina made extremely smooth and precise focusing mechanics and every part looks thick and heavy duty, I personally think that these lenses are able to be used for centuries if properly served and greased. New mechanics design requires alternative ways of assembly path, so now these lenses need to be opened from the front. Though it is still possible perform minor maintenance steps without a risk of misaligning optical structure, because each optical element remains inside of well calibrate optical module frame, and position of each optical piece remains exactly same after assembly.

The disassembly steps are relatively simple if you know the sequence of actions. Large challenge of modern Voigtlander lenses - is extensive amount of glue is applied to every bolt, so extra accuracy and precautions are required to accurately unscrew bolts without breaking screwdriver or stripping bolt head. 

It is recommended to serve these lenses in professional shops, though if you absolutely willing do run it as a DIY I'd highly encourage you first practice unscrewing stubborn preliminary glued bolts on some cheap equipment first. I personally had bad experience of partially stripping bolt heads on some quite expensive lenses in the past, just because loosened attention for a moment or didn't count on proper force needed to break the bolt glue. It took some practicing and time to learn how to do it safer and keep bolts in original shape. Sometimes a drop of acetone helps, in other cases holding micro-screwdriver with pressure applied on handle edge and minor rotation by grabbing with pliers is a better idea. For this Voigtlander 50mm F1.2 Nokton lens disassembly I had to use second method for all 6 bolts.