MOD - click-stop aperture - Pergear 35mm F1.2 lens Fuji X mount

This article shows how to modify Pergear 35mm F1.2 lens in Fuji X mount to introduce custom click stops for aperture ring.

Pergear 35mm F1.2 lens has click-less aperture ring. I’m big fan of compact 35mm lens, and prefer to have clickable aperture, so value can be set by counting clicks while looking into camera viewfinder. Fortunately there is a relatively easy way to make it work for this lens model.

Scary lens drilling, again

Well, not actually the lens but part of the frame need to be modified. One of the common way aperture clicks are implemented in most lens including Fujinons XF – there is a small metall ball loaded with spring, that is catching socket each time you are rotating aperture ring to next value.

Exploratory disassembly of Pergear 35mm F1.2 lens shows one good area to allocate spring with ball – it is the external aperture ring itself. It’s thick enough to fit 5mm x 1.6mm tunnel. However in this case I’m going to direct it vertically.

After discovering inexpensive source of 1.6mm metal balls, I’m using them for such projects. So after disassembling, I’m wrapping ring with aluminum foil and marking place for drilling.

Then I’m using 1.2mm drill bit to make 5mm deep hole.

After that I’m switching to 1.6mm drill bit, making that tunnel wider, and finally smoothing edges using sharp knife.

Now it’s time to find or make small 5mm long spring, and take 1.6mm metal ball from mount parts of Vivitar lens.

Spring and ball nicely fit there. I’m glad it worked from the first time. In some previous modifications of Mitakon I had to re-drill another hole because first one was not accurate enough. Looks like drilling with 1.2mm bit then with 1.6mm bit making it accurate enough.

Marking aperture click stops positions

Then I’m wiping out grease on the ring that sits between aperture ring and mount ring. It’s time to cover with pencil area where the ball will be moving when aperture ring is rotating.

Next step is to assemble Pergear 35mm F1.2 lens back, and move aperture ring from F1.2 to F22 few times. After disassembly you’ll have trace of the ball movement.

I’m drilling few spots at the ends of marked trace curve, using 1.2mm drill bit first.

Then I’m assembling lens back, and checking if ball properly fits that newly drilled sockets. Yes, it works! It’s time disassemble the ring again and mark another aperture value stop positions.

I’m drilling each socket using 1.2mm, then 1.6mm, and finally 2mm drill bit. Sockets should be about 1mm deep, so n=ball is catching them with ‘click’ but also can easily escape when rotating ring further. Just in case something goes wrong – there are two more sectors on this ring to repeat the process. However in this case I made everything right.

Final step is cleaning edges with knife, and wiping out ring. You may want to add some grease to flat surfaces.

Assembling and painting

After assembling Pergear 35mm F1.2 lens its modified aperture ring works great – I clearly feel and also hear quiet ‘click’ at each marked aperture value.

Finally I’m using red paint to fill in the engraving areas indicating ‘ft’ focusing distance scale and also central diamond mark.