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Jury rigged adapter

Started Sep 8, 2018 | Discussions
petrochemist Veteran Member • Posts: 3,619
Jury rigged adapter

My latest macro lens was a fairly cheap c-mount microscope objective, that claimed high magnifications with good working distance.

When it arrived I wasn't too surprised to find it vignetted on MFT, quite severely at the lower magnification setting but not too bad at maximum zoom. Working distance appeared very similar across the zoom range (there's no separate focus control). Tests on ancient family photo showed it to be impressively sharp clearly showing decades worth of surface scratches (Unfortunately the photo I was copying wasn't all that sharp but it's the only one we have of these great great grandparents and they were tiny in it - not much more than 1cm square!)

More annoying was that the magnification was only half that claimed, due to the c-mount adapter including a 0.5x relay lens, and this wasn't just an unscrew job.

After waiting a week for comments from the supplier I decided to have a play. A single grub screw allowed removal of the relay lens but also removed any useful mount. - Fortunately luck was with me, I have a good number of spare adapters to play with and my first real effort worked well!

A T2 adapter has a few mm spare between the outside of the lens and the inner face, so wasn't an obvious choice, but with the core screw thread removed I found the flex I was using to extend a power lead made a perfect filler. With the flex in the T2 core I could (only just) push the lens body into the reduced ID. The fit was easily tight enough to hold the lens in place during initial testing, and has now been firmed up with a little hot melt glue.

Connecting the T2 adapter to my camera via a EF-MFT helicoid (& PK-EF adapter) has got the lens working much better. At maximum zoom (4x marked) 6mm fills the frame at a working distance around 9cm, no vignetting is seen till I zoom out more than half way (2x marked).

The lens mounted on MFT  - The background a Cyanotype recently made by my wife.

A quick play afterwards confirmed suspicions that it's not as useful connected straight to my DSLR, vignetting significantly on APSC. but not as bad as I would have expected.

At maximum zoom it seems to give much slightly more magnification, and only minor vignetting - zoomed out it will focus much further away I grabbed a quick shot of my PC screen from across the room (no longer even approaching macro) and it still had a long way to go.

 petrochemist's gear list:petrochemist's gear list
Pentax K100D Sigma SD14 Pentax K-7 Panasonic Lumix DMC-GF2 Pentax Q +19 more
OP petrochemist Veteran Member • Posts: 3,619
Re: Jury rigged adapter

Here's a quick test shot of an engraved millimeter scale using the modified mount at full magnification https://flic.kr/p/29RYyk1 I make it about 6mm across the frame, which is 3x on MFT

Now I need to work on some interesting examples...

Now got a selection of test shots in an album <a href="https://flic.kr/s/aHskHPvBS5" rel="nofollow">flic.kr/s/aHskHPvBS5</a>

 petrochemist's gear list:petrochemist's gear list
Pentax K100D Sigma SD14 Pentax K-7 Panasonic Lumix DMC-GF2 Pentax Q +19 more
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