Disassembly - MS Optics Apollon 36mm F1.3 Leica M mount lens

 MS Optical lenses are well known for their unique compactness, interesting rendering and practical minimalistic design. The model I'm going to explore more in this article is a MS-Optics Apollon 36mm F1.3 lens in Leica M mount. Big thanks to Fred Miranda for landing his lens, and additionally for his own effort and knowledge sharing on initial disassembly explorations which made this discovery process easier.

Intro

Lens is extremely compact, which is typically achieved by reducing a number of moving mechanics and transmission rings. MS-Optics Apollon 36mm F1.3 indeed has only three moving sections, similar to Voigtlander 40mm F2.8 lens - mount frame, focusing core and aperture ring. I don't count here aperture blades assembly module, which is anyway complex assembly in any lens.

Extracting Lens Core

Optical core is built as a single unit, which can be released by unscrewing CCW retention ring. Fred discovered earlier that overtightening this retention ring will make aperture ring rotation too stiff, and soon you will see why.

There is square detent on the focus ring edge. After unscrewing retention ring simply grab aperture ring and accurately pull off the optical core. Do not touch black surface - it is covered with grease for smooth rotation. The aperture transmission bolt will slide off that rectangular detent.

This is how aperure control is simplified in MS-Optics Apollon lens - whole optical core frame is acting as aperture ring. When rotated inside focusing frame, aperture transmission bolt remains at same inner groove of focus ring, which is making aperture module to close/open blades.

Fred also discovered that rear module of optical core can be unscrewed CCW, which provides access to the aperture chamber and inner lens surfaces for cleaning.

Dismounting RF couple ring

This part of disassembly is extremely hard, due to MS Optical decision to secure RF couple ring on focusing core with strong glue. Fred tried to unscrew it using spanner wrench but RF ring did not move, glue is holding micro-thread too strong. Then we decided to give it a try by myself, using some advanced methods.

First of all I'm unscrewing CCW focusing pin.

Then I'm crafting custom rectangular solid brass wrench-plate with thicker shaped edges. It is secured in low profile vise between slightly elevated aluminum bars. Finally I'm adding two strips of thick leather to protect lens mount.

Edges of brass wrench are going into rectangular detents of RF couple cylinder. I'm focusing lens closer to 0.8 distance to elevate RF ring inside frame until lens frame mount sits firm on leather surface. 

Then I'm wrapping tight long strip of leather around focus ring in CCW direction. It allows to grab thin focus ring with stronger force.

Now the most challenging phase goes. I'm grabbing leather cylinder firm, and pressing from the top to not allow brass wrench escape from RF ring detents. Next I'm performing very strong but well controlled sequence of CCW torque moves... At first, nothing happened, but after numerous attempts I heard loud "click" sound indicated cracking the glue.

It is important to note that I soaked thread edges with acetone, and later put focus frame to freezer and after that let it warm up, to loosen the glue a bit. Even that stems helped only little, it still required a lot of force to be applied to break the glue.

It took extra 4 full turns to unscrew lens from RF couple ring, and first few turns required significant effort.

After that I used acetone to dissolve and clean glue from RF ring thread, and from focus cylinder thread.

Dismount focusing core

With RF couple ring removed, focus ring can travel further until focus pin location is reaching first "8" of DOF scale . This is the point where focus thread is detaching.

I found inside thin plastic ring shim that is limiting focus rotation pass infinity mark for few degrees. This particular MS-Optics Apollon 36mm F1.3 lens was not able to reach real infinity focus, so later I need to replace plastic ring shim with a bit thinner one. For now I'm simply removing it to access infinity focusing.

At this point focusing thread can be cleaned and greased if you need to. I'm going to assemble lens back in a reverse order.

Note - aperture transmission silver bolt should fit into vertical groove on the inner wall of focusing frame.

Cleaning and recovering RF couple ring

Here is a closeup of micro-thread on RF couple ring, after complete cleaning out securing glue.

I had to apply a lot of power unscrewing RF couple ring which added scratches and minor edges deformations of rectangular detents. I'm using 1000 grit sandpaper to polish off deformations, and using acid to darken aluminum to original black non reflective color. Now it looks like new again.

Here is a view on focus core cylinder micro-thread, also cleaned from glue using acetone and cotton fabric.

Assembling and tuning RF couple precision

The optical core is inserted into focusing core and next step is to add and tighten the retention ring in CW direction.

Check that the aperture ring is rotating with desired effort, otherwise gently tighten/loosen the retention ring.

Now accurately screw on the RF couple ring in CW direction. It takes 4 full turns until protruding leaf edge almost fits edge of the lens mount.

At this point RF couple ring radial position can be easily tuned to align camera RF indication. Once precise RF position found, mark it using pencil. Later you will need to secure RF ring by adding a little amount of loctite glue to one tiny spot of micro-thread. Don't add too much, to keep disassembly easier.

Conclusions

MS-Optics Apollon 36mm F1.3 lens disassembly was quite a challenge. Main problem is over excessive amount of glue used to secure RF couple ring, making it also impossible to fine tune RF precision 

Though physically possible but quite hard, Apollon can be refined through explored maintenance steps to bring it to adjustable shape. I'll let Fred continue with RF precision calibration, he already had great success with calibrating MS-Optics Petz model by tweaking radial position of RF couple ring. Now Apollon 36mm F1.3 lens can follow similar DIY calibration pattern and became one of the rarest copies well tuned for precise Leica rangefinder use.