Disassembly – Pergear 12mm F2 lens (Fuji X mount)

Today I’m disassembling wide-angle Pergear 12mm F2 lens which was earlier reviewed on 35mmc.com. This guide may be useful if you decide to replace the grease or repair focusing mechanics. In case you just need to calibrate infinity focus precision, it can be done without disassembly by following focus calibration guide.

Disassembly steps

I’m starting disassembly from the rear area. First unscrewing three silver bolts on the mount ring.

Now I’m removing the mount ring. It’s nice to see the brass calibrating plate under it, looks like Pergear engineer using them for precise tuning the mount thickness for different camera systems.

Next step is to unscrew three black bolts sitting deep in sockets. Unfortunately it’s not easy – this Pergear 12mm F2 lens sample has quite strong glue around that bolts. I’m using drop of acetone for each bolt and waiting for few minutes until the glue slightly loosens. After that I’m accurately unscrewing them by applying initial torque force to break the glue remains, and then unscrewing bolts completely.

After removing black ring, I’m removing the external aperture ring.

Now it’s time to use wide flat screwdriver to unscrew long brass transmission bolt. It connects internal aperture transmission ring with aperture lever.

Then I’m removing aperture transmission ring.

Now I’m checking that focus ring is at infinity mark, and then marking with pencil position of “red diamond” on the front frame edge. It is important for proper helicoid assembly. Make sure that focus ring is not rotated after this and remains at infinity mark.

Next step is to accurately unscrew four silver bolts and pull out brass helicoid guiders. WARNING: do not unscrew two bolts marked with red arrows, most likely they are holding the aperture module inside lens core, if you unscrew it may get misplaced, and complex optical disassembly will be required to fix that.

Remember helicoid guiders and bolts positions, it is important to put them to exact same location during assembly.

Then I’m holding front lens frame, and rotating upper lens frame in CCW direction. After making two full turns it will look like on picture below. Remember to keel focus ring infinity mark right at “red diamond” mark.

I’m making one more full turn, and then very slowly keep rotating and trying to elevate after each few degrees. This Pergear 12mm F2 lens sample has detaching point at about 0.35 distance indicator. It is important to attach it back and catch the helicoid thread at exactly same position when assembling.

Helicoid core has multiple threads (about 10), so if you mistakenly catch one neighbor thread during assembly, lens will under/overfocus, and re-assembly will be required.

One interesting thing noticed – there are three bolt ends visible from this side, which means that front lens naming plate around front glass can be unscrewed CCW, and there shoul dbe three black bolts under that nameplate. I’ll probably give it a try later and update article with more details on that.

At this point you have convenient access to helicoid core, and if required – to rear optics as well.

Finally I’m unscrewing half way three small bolts on focus ring and removing it from the helicoid outer frame. Helicoid middle ring can be unscrewed, but I’m not doing it this time. If you need to do that for grease replacement – make sure you mark rings position first with permanent marker.

Focus ring has grooved area for focus rotation limiting by the rectangular pin on helicoid frame right under the “red diamond” mark.

Assembly steps

Now I’m assembling everything back in a reversive order. However there are few important steps to take.

After attaching focus ring to frame at infinity mark I’m securing three bolts slightly one by one until focus ring moves to proper position.

Then I’m connecting helicoid outer frame at same point it was pulled out, and making tree full turns in CW direction, and then a little more until “red diamond” mark fits the pencil line. Then I’m checking that helicoid guider sockets are properly positioned and inserting helicoid brass guiders there.

Then I’m securing helicoid guiders with four bolts, and checking that focusing is smooth.

Next step is to insert aperture transmission ring, and match the bolt thread location with inner aperture lever.

I’m screwing in long brass bolt slowly, and centering aperture lever. NOTE: this bolt should catch the inner lever, but should not be completely tightened.

After attaching aperture ring it should rotate smoothly and moving aperture lever inside.

Finally, attaching rear ring, screwing in three black bolts (I cleaned them from glue before that). Then putting brass shim plate and mount ring and securing it with tree silver bolts. Done!

Brief conclusions

Pergear 12mm F2 lens mechanics is very well designed with all metal parts inside. All components are durable and machined with high precision, and all inner surfaces are also anodized – even the helicoid thread, which is very good to see – that prolongs the life of focusing mechanics. Pergear engineers are using lots of grease in friction areas, and I like to see brass helicoid guiders. Mechanics operates very well and it’s relatively easy to disassemble this lens in general.

The only disappointment is to see the use of glue on second set of bolts in the mount area – it may be difficult to unscrew them for maintenance. Without using glue dissolver (like acetone) it is possible to strip out bolt heads, which will require complex process of bolts extraction and replacement.

There is also plenty of space to add custom aperture click-stop mod, which I’ll probably do one day as well.

3 comments

  1. Thank you for the detailed breakdown. I bought this lens several months ago and I’m enjoying it. I think it is a bargain. Chinese makers certainly are striving for quality and value. I did a mini review on the DPR Forum, with brick wall tests here — https://www.dpreview.com/forums/post/64722455 and high res samples here — https://www.dpreview.com/forums/post/64762345. Micro Four Thirds users might want to take note of my adapted lens hood which is better than the stock hood at reducing flare from light sources outside the frame.

    For stills the results are quite good, even excellent when stopped down, but I found that the internal construction is questionable: when the focus ring is rocked back and forth, the image shifts in the OVF of my Olympus EM1-II camera, making this lens unsuitable for video shooting. Maybe it’s my particular lens sample, but you also might check for this anomaly if you still have yours.

    Liked by 1 person

    • Thanks for interesting details about image shift. I can confirm same behavior with my sample, perhaps the position of two brass helicoid guiders can be fine-tuned to correct that shift. I may give it a try once find time over weekend.

      Like

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