adapter for microscope lens to OM mount?

[Harold Gough]

[Ecooper]

[rjlittlefield]

[Harold Gough]

RIk,

I'm not sure if this helps but it is factual.

I have just examined my Olympus m4/3 and OM cameras and lenses. In both cases the red dot on the camera body is at about 10 o'clock on the camera flange. Also, the red dot on a lens/adapter/tube is at 12 o'clock when locked on. This also applies to my M42 to OM adapter (the one without the rear correction lens).

Things are different with my Leica-R lenses, where the insertion (dot not marked on my adapter) is at nine o'clock (at the position of the release button) and the locked postion at 11 o'clock. This gives some scope for error in a small, mixed-mount production line.

Harold
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My images are a medium for sharing some of my experiences: they are not me.

[rjlittlefield]

[Harold Gough]

Rik,#

Sorry. Nobody talks much about 4/3 these days so I jumped to m4/3.

Referring to my 4/3 lens this time:

The red, green and orange items coincide. Orange (oval recess) is +/- 90 degrees from the red dot; green (stop screw) is about 140 degees from red dot.

The red dot on front (4/3) of 4/3 to m4/3 adapter is as for OM or m4/3 (about 10 o'clock). Red dot on 4/3 lens has to be aligned with red dot on mount to insert and is at 12 o'clock when locked. This suggests something non-standard in your mount.

When it comes to comparing the bayonet mounts (male on lens) for OM and 4/3 they are almost opposites: where there is a part-circle flange on one there in none on the other, such that it is rotated by 60 degrees or so (a guess!).

If this has not totally confused you I hope it is of some help.

[Edit] A cross-eye stereo pair, straight from the camera (rush job, I am on child care duty). OM 38mm bellows on left, 35mm macro 4/3 on right. Both as on camera i.e. red dot at (approx.) 12 o'clock.



(A quick return with a sharpened single image):



[Edit ends]

Harold
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My images are a medium for sharing some of my experiences: they are not me.

[enricosavazzi]

Hi Rik,

what you have is almost certainly a 4/3 adapter. Many of these adapters are incorrectly advertised as "OM compatible" on eBay, but OM is properly only applied to the Olympus film SLR system, not the 4/3 nor the Micro 4/3.

Both the 4/3 and the Micro 4/3 male bayonets have what I would call a Nikon-style recess at 3 o'clock (looking toward the camera female bayonet) where the locking pin clicks in. As your picture of the Olympus OM lens shows, the male OM bayonet has instead a locking tab that springs radially outward to lock into a notch machined into one of the three female bayonet flanges at approximately 1 o'clock.

The 4/3 and Micro 4/3 male bayonets are geometrically similar, but the Micro 4/3 has a diameter a few mm smaller and there is no way to lock a Micro 4/3 lens into a 4/3 camera (or vice versa).

I also find it impossible to fit an OM lens into a 4/3 female bayonet (the only one I have at hand is a Panasonic 4/3 to Micro 4/3 adapter). I don't have any male 4/3 bayonet at hand to try fitting it into an OM female bayonet, but it might work the way you found (except of course it should not lock).

Edit: I did find a 4/3 male bayonet, and there is no way to insert it into a (genuine) female OM bayonet. The bayonet flanges are always in the way along the whole 360 degrees rotation. Your adapter is probably machined slightly out of specs.
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--ES

[Harold Gough]

[rjlittlefield]

Thanks! I understand now.

So, what I have are two adapters, both made to 4/3 spec, but one of them having at least one smaller tab that lets it also work with an OM mount by mismatching the red dots appropriately.

--Rik

[Harold Gough]

"Tab", the word I needed!

For some time I have been using OM plastic body caps on 4/3, there being just the tabs and nothing else to limit use.

Unfortunately, "OM" is used incorrectly for most of the adapters on Ebay where 4/3 should be specified.

Of course, apart from potential use on extension tubes, bellows and suchlike, there is no point in being able to attach OM mounts to 4/3, as the flange to sensor distance is about 7.3mm too short. (In passing, the M42 lenses on OM need a reduction of 0.5mm, hence the correction lens for distant focus).

Harold
_________________
My images are a medium for sharing some of my experiences: they are not me.