Easy DIY APS-C DSLR adapter for Leica stereos (trinocular M series, S series)

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Scarodactyl
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Easy DIY APS-C DSLR adapter for Leica stereos (trinocular M series, S series)

#1 Post by Scarodactyl » Fri Jan 24, 2020 5:55 am

NOTE: I have so far only tested with on an m-series scope. I am pretty sure it will work on an s-series as well since they use the same camera mounting hardware, but there's an outside chance the S series might not project as big of an image circle. Please don't be mad at me if it doesn't work on yours, but either way please post your results!

If you have a trinocular Leica stereo microscope (a Leica S6D, an S8 Apo, an S9(?)/S Apo (?) or an m series or z series with a trinocular head) and have tried to mount a dslr on it, chances are might have come across this article over at Micscape: http://www.microscopy-uk.org.uk/mag/art ... photo.html
It's a nice helpful overview of the author's attempt at setting up a camera on this particular type of Leica trinocular port using official Leica parts. He did everything right, and yet this ended up being a somewhat difficult and expensive process for him and ultimately didn't get him quite where he wanted. This is pretty typical--DSLRs are kind of an afterthought in Leica's adapter lineup so you have to get a rare and expensive 1.6x adapter for aps-c (or 2.5x for full frame) on top of the required 1x adapter, yielding a tall tower of expensive metal and glass.

I recently got my hands on an m-series trinocular head, which uses the same camera mounting hardware: a hole at the top of the head with a thread which accepts a Leica 1x (part no 10445930) adapter, which in turn gives you a standard Leica 37mm mount to accept a camera adapter. The way this is laid out the tube lenses (these take the stereo images produced by the zoom body, which are focused to infinity, and focus them for the eyepieces or camera) are pushed up into the base of the eyepiece tubes, and the trinocular port has no tube lens at all, meaning it produces the image still focused at infinity. This infinity-focused image just produces a blur on a camera, so the Leica 1x adapter contains a 200mm focal length tube lens (the article mistakenly calls this adapter lensless, but it isn't). That projected image can then resized up or down by additional lenses to fit your particular camera sensor.

This is a bad setup for our purposes--it's way too expensive and elaborate since a 200mm tube lens can project an image that is perfectly sized for APS-C with no additional hardware. Either the 1x adapter crops the image some, or it's physically arranged so the camera sensor on a dslr can't get low enough to get a focused image, but either way you can't direct project onto a DSLR sensor with what they provide.

So the best solution is to throw out the Leica tube lens entirely (or rather, not buy it), and provide your own 200mm tube lens instead. Leica stereos (and modern stereos in general) don't do corrections in the eyepieces, so the tube lens only has to be a 200mm lens of decent quality. You can find good options by seeing what experts use for high end infinity objectives like the Mitutoyo M Plan Apo series. In this excellent test the Kenko #5 enlarger lens proved to have an exceptional quality-to-price ratio. There are better tube lenses but, frankly, we're not dealing with scopes that have anywhere near the resolution or aponess of a Mitutoyo, so it's unlikely the difference is going to be noticeable. Though even if you bought a top end option it would still probably cost less than the Leica solution.

Here is how I made mine. The outer threading of the trinocular head is 38x1 or something very close (37 is definitely too small), so I got a 38x1-m42 adapter to get it to a more standard thread. This adapter is very loose until it's screwed all the way on, then it gets nice and grippy. I then threaded a female-female m42 adapter onto that, because you want to present a female thread for the rest of this.

The Kenko #5 comes in a few different sizes--I got a 49mm example. This needs to be attached to the camera at infinity focus, meaning about 200mm from the camera sensor. To do this I attached a male m49 to female m42 adapter, enough empty m42 spacers to focus it to infinity (including an m42-m42 helicoid in the stack to allow fine focusing), and then an m42-canon adapter. From there you just need a female 49mm to m42 adapter to thread it onto the adapter you put on the trinocular port.

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It works, and I think it works well. The image is perfectly parfocal, the sizing is perfect, and image quality seems quite good from a quick test shot (single shot no stacking) of an amber bug in darkfield illumination.
(click the image for full size)
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The image is almost a perfect rectangular crop from the view in a standard 21mm eyepiece.
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I think this is a better solution for aps-C than Leica provides, and it's definitely a heck of a lot cheaper. From reading in another thread the addition of a high quality 1.6x teleconverter would probably make this suitable for full frame too, but I have not tried that.

You can do something very similar to this on the Nikon SMZ-U, but that will be another post at some point.

PeteM
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Re: Easy DIY APS-C DSLR adapter for Leica stereos (trinocular M series, S series)

#2 Post by PeteM » Fri Jan 24, 2020 3:56 pm

Thanks for that informative post, Stephen.

Scarodactyl
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Re: Easy DIY APS-C DSLR adapter for Leica stereos (trinocular M series, S series)

#3 Post by Scarodactyl » Sun Feb 13, 2022 12:37 am

I recently had another crack at this, since I got my Wild M10 gem microscope setup...set up. viewtopic.php?f=24&t=14873
I have a Leica clone trinocular head on that one which uses the same hardware. The above solution is OK, but has one major issue: it puts the camera higher above the head than I would like for a microscope that tilts. Plus, now I have a 3d printer and the whole thing can be streamlined.

The official solution (https://spectraservices.com/product/10447436.html) is still pretty pricey, though I was a bit wrong about it in the initial post. While they do have a separate 2.5x adapter for full frame that fits into the 1x adapter, the 1.6x adapter for aps-c skips the 1x and attaches directly to the head. So this is basically trying to recreate that design.

On these heads there is no tube lens at the top and you have direct access to the infinity-focused intermediate image. As such all you really need is an achromatic doublet of the right focal length, something to hold it in position and sufficient spacers to put your camera at the right focal point. The adapter has m38 threads on the inside to thread onto the head, m42 on the outside to accept cheap spacers and a helicoid and accepts a 1 inch 200mm fl Thorlabs achromatic doublet via press fit.
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200mm is perhaps a bit long--some Wild/Leica stereos would have no trouble covering aps-c with a shorter fl lens. however, with the intermediate attachment on my M10 the FoV is restricted. 200mm ended up giving perfect framing, right within the FoV given by 10x/21 eyepieces. Even with the improved design it's a bit tall over the microscope, but doesn't seem to mind the mild tilting that it will have to deal with.
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(click for full size).
In theory you might get better results with a better-corrected lens than just an achromat, but looking at the official Leica 1x adapter it appears to have a simple two element achromat in the base so I doubt it's too critical. Overall I'm pretty happy with the photographic results--the corners are weak at lowest and highest mag but really no more so than they look through the eyepieces. A stereo is never going to be the best tool for photography but the M10 seems like it should be an excellent tool.

I'll try to get the design up on thingiverse in the future--the site is kind of unreliable and I'm currently not even able to log in.

edit: I put it up on the Prusa site instead https://www.prusaprinters.org/prints/13 ... amera-adap

Of course, all of this is kind of moot until I figure out replacing or fixing this head, since it came to me misaligned. Worst case I think I can probably manually adjust it one way or another, though I am not 100% on that.

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patta
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Re: Easy DIY APS-C DSLR adapter for Leica stereos (trinocular M series, S series)

#4 Post by patta » Mon Feb 14, 2022 9:36 am

That is very nice; I just went to a similar road, to use infinity-corrected objectives.
Just, instead of the doublet, used a 200 (or 135) mm telephoto objective as tube lens, so both focuser and spacing are already included. Drawbacks: can't focus after infinity; maybe the microscope body or objective work better with just a doublet; the 200mm telephotos are cheap vintage and have likely less contrast than a plain, new doublet. Somebody tested them already I'd guess!

I dream to have somewhere a collection of "tested" 3D files for microscope adapters, like this 38mm, plus others
Could you post the dimensions? In particular the distance of flanges 38mm - M42 and the position of the lens.
Thingiverse, or Prusa, not sure which will be more reliable...

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