DIY: Make a Micro four thirds adapter for Pentax 110 lens

The introduction of the micro four third system on Panasonic and Olympus brings demands for lenses that are a bit smaller than the existing 35mm SLR lenses. The image sensor size is exactly half the size of a full 35mm slr film. This means a 50mm lens on m43 will have the crop factor of a 100 compared to a 35mm full size. What you are gonna need is lenses ranging from 50mm and down, and they should rather be small yet light sensitive. The old Pentax 110 system is a perfect optical fit for the Micro four thirds, as the Pentax had a half-frame system. The lenses are thus optimized for that, being much smaller (almost too small). The adapter can be bought off Ebay, but they cost around EUR 45. This is more expensive than the 20mm Pentax lens itself. I decided to build an adapter myself. And here is the first test shots.


I drilled and cut the rear lens cap so it could fin into the lens ring. I cut out some rubber to fit inside the lens cap. It prevents the lens from slipping off. The whole operation took me a couple of hours.

110 Lens, rubber pad, c-mount micro ring, c-mount adapter ring.

Pentax 110 rear lens cap drilling

First I drilled a big hole in the lens cap

Then I cut down the sides a bit until i could screw it into the micro ring

Home-made Pentax 110 lens adapter for micro four thirds

The lens cap was then screwed to fit into the micro ring. I adjusted the number of turns so the lens had just the right distance from image sensor. I checked that focus at infinity worked. The rubber pad was cut to fit into the lens cap itself, and also have a hole for light to come trough. It makes the lens stick to the lens cap better. The mount is now ready for the lens.

Olympus Pen with Pentax 110 18mm f2.8

Olympus Pen E-P1 ready to go with Pentax 110 18mm f2.8

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One response on “DIY: Make a Micro four thirds adapter for Pentax 110 lens

  1. Pingback: Pentax 110 system 18mm 2.8 test « Henning makingit's Blog·

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