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Pentax 110 18mm/24mm/50mm by MFT Adapter with diaphragm
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PostPosted: Wed Feb 05, 2020 6:19 pm    Post subject: Pentax 110 18mm/24mm/50mm by MFT Adapter with diaphragm Reply with quote


I'd like to share here my experience with Pentax 110 lenses when used with an adapter from Pentax 110 to MFT with integrated diaphragm.

Maybe I first show some picture made by the lenses before I show the adapter.

I own the 18mm, 24mm and 50mm Pentax 110 lense, which all are very compact. Mainly I use the 18mm and the 50mm lense. In some few cases also the 24mm lense with its special ability to look throug oculars and its very compact size. With the adapter I can stop the lenses down which allows more depth of field and maybe more important for those lenses to gain more image quality.

I use the lenses on a Olympus E-PM1 which I bougth in used condition without lens for quite low money. I also use a small resolution of some 5MPx only which would make 20MPx on full format for not asking to much from the lenses.

Due to the small size of the camera and the lenses I have it always in my backpacker even in daily work.

Pentax 110 18mm at ~5.6-8

Pentax 110 18mm at ~8

Pentax 110 18mm at ~11

Pentax 110 50mm at ~8 (most likely with 2x digital zoom)

Pentax 110 50mm at ~5.6 (most likely 2x digital zoom)

Pentax 110 50mm at ~8

Pentax 110 24mm ~F4

Pentax 110 24mm at ~8

Pentax 110 24mm through (bad) Binoculars 10x50 without any adapter between lense and binoculars

The two main parts of the adapter are an adapter without integrated diaphragm and a diaphragm (12mm inner diameter) bought at ebay. The self made part is mainly a lever which is made of 4mm x 1mm brass.

Front with iris and bajonett

Bajonett removed

Back view

A part of the 4mm x 1mmm is bent into a ring which is not totally closed; in the gap/notch of the open ring the operating pin of the diaphragm engages. The actual lever also consisting of 4mm x 1mm is soldered into a filed cut out of the ring and slightly bent (before soft soldering) according to the recession of the adapter. The lever's movement is restriced by the section of a circle cut out in the adapter. By the way, I just used a manual iron saw and a file to do this. The diaphragm is glued on the black plastics seen from the back (with super glue). The black plastics with its bezel to avoid vignetting is glued onto the adapter with double sided adhesive tape (since I thought it may be a good idea to make the iris exchange- and adjustable). I planned for a more sophisticated light seal for the lever made of thick black paper. So far it wasn't needed. The only thing was to reduce the gap for the lever to some 1.5mm by glueing a plastic part onto the bajonett ring filed to shape.

By not directly operating the pin of the diaphragm and by the restricted movement of the lever it is not possible to transfer unhealthy forces on the diaphragm. It works now for two years without fault and I still think that it is somehow a primitive but good construction.The only problem is that I need to re-bent the bajonett part of the adapter from time to time (approx once per yr) which is an issue of the bought part. For that reason I never bought the 70mm lense and the zoom because I think those are too heavy for the bayonett. And hence I cannot tell you in a definite way whether they work with this adapter. I would say that they work according to my technical reasoning. There is an adapter with a diphragm which can be bought. This adapter however uses an iris with only 8mm inner diameter which is too small in my opinion. The opening of the lenses is 8mm, but due to necessary distance to the lens the diaphragm needs slightly more.

Last edited by pandreas68 on Wed Feb 05, 2020 9:14 pm; edited 2 times in total

PostPosted: Wed Feb 05, 2020 8:37 pm    Post subject: Reply with quote

That's cool!
I wonder how well it works (behind-the-lens aperture rarely works well, unfortunately)

PostPosted: Wed Feb 05, 2020 8:53 pm    Post subject: Reply with quote

Yeah, vignettor, although 110 cameras same arrangements. Maybe Pentax lens designed for it.

PostPosted: Wed Feb 05, 2020 9:24 pm    Post subject: Reply with quote

Yes Pentax 110 cameras are designed for that. The diaphragm and the shutter on the Pentax 110 is the same thing.

One of my information source was Rick Oleson which was one of my reasons that I bougth a now Pentax 110.

The second reason is that I know the Pentax 110 since I was a student and came across that its lenses can be adaptet to MFT due to the same imige circle. Now in the modernized variant it is a lot fun for me.

Vignetting is an issue. My adapter allows up to approx f/16 but beyond f/8 vignetting gets worse. So they behave somehow different to normal lenses.

PostPosted: Wed Feb 05, 2020 9:28 pm    Post subject: Reply with quote

Ah, I forgot to write that all pictures are handheld. For pictures with 1/4 or 1/2 sec some walls or whatever is used.