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 Post subject: Easy diy camera adapter for bausch and lomb stereozoom 7
PostPosted: Sun May 12, 2019 8:04 pm 
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This is a problem I've recently run into while setting up my dad's microscope, and is probably pretty common in gem circles. You have a nice old gemolite, and you just got an SZ7 with a trinocular port for it, but you're not sure how to attach your camera to it. If you have the original sz7 trinocular port that has a threaded hole then what you need is a particular B&L threaded tube that accepts a 23mm eyepiece at the top. This is now just a third ocular, so you can use standard eyepiece adapters for a c-mount camera of choice, or a 23mm projective eyepiece and a standard microscope to camera adapter with a ~1" clamp.
Most SZ7s on the market, however, seem to come with an unthreaded trinoc mount. This one does not have any threads--instead it accepts a 27mm tube that is held in place with two set screws. It looks like this:
Image
Optically it's exactly the same, but as far as I know Bausch and Lomb didn't make an eyepiece tube to fit it. They had a few purpose-specific adapters, mostly for polaroids, which are scarce and probably not useful anyway. This guide is for making your own eyepiece tube, and on top of that how to attach a DSLR to it.

What you need:
A bunch of M42 spacers, order at least 5 of those sets of three just to be sure (~$3.50 per set $18 total) --I'll try to get a tally of how many are used on the final version later
1 M42 female to C-mount Male adapter (~$15)
1 male to male m42 adapter (~$5)
1 m42 helicoid (or 2 optionally) (~20/ea)
1 27mm od 25mm id carbon fiber tube end protector (~$4 for 2)
1 ocular off a broken b&l stereozoom (variable, don't spend much)
1 b&l stereo 10x eyepiece (for testing only, use one from an ocular)
For a DSLR: 1 Nikon 2.5x projective eyepiece (I typically pay about 40 dollars for a used one)
For DSLR: 1 m42 adapter for your camera (~$5)

Total estimated cost ~100ish dollars, depending. That is sort of a lot for a self-made solution, but given what a commercial one costs (eg https://www.martinmicroscope.com/produc ... icroscope/ ) it's not bad--and I suspect the results are as good or better.

For the first part, a 27mm tube to m42 adapter, I found a very handy part on eBay. This is a metal cap that is slipped into the end of a carbon fiber tube to prevent the ends from fraying. Its outer diameter is 27mm and its inner diameter is 25mm. These are available very inexpensively, here is one for example.
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They fit perfectly in the trinoc port. Also conveniently, the inner diameter of 25mm is just about the diameter of a male c-mount thread. A standard male c-mount to m42 adapter almost fits right inside.
Image
All it takes is a bit of modification to get them to fit together perfectly (this could be done with sandpaper, but I used a bench grinder because it's faster)
Image
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A bit of JB-weld and they're stuck together forever, and you can now attach standard m42 spacers and dslr adapters to the port. You'll need to add the male-male m42 adapter here to get male M42 threads facing up (as most m42 dslr adapters accept a male m42 thread.)
All you need now is a convenient way to hold an eyepiece in the middle of those spacers. As it turns out, the ocular off a b&l stereozoom microscope--any stereozoom, 1-7--fits perfectly inside a standard m42 spacer, well enough that you can just let it sit in there and not further secure it even for a microscope with a tilting base.
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So just attach an appropriate length of m42 spacers between these two parts. It needs to be about 5 inches from the base to the ocular, but you can tell you have it right by getting a nice bright subject under your scope in sharp focus, putting an eyepiece in the ocular and adjusting the length until the image in the eyepiece is in focus. I found I got close enough by using normal spacers, but it could probably be improved by adding a helicoid for fine-tuning, as it is pretty sensitive to getting this length correct.
Once the b&l eyepiece is in focus you can now use a standard eyepiece adapter for your camera of choice. I haven't done much with smaller c-mount cameras so you might be able to remove the ocular entirely and do direct projection with an m42-cmount adapter.
If you want to use a DSLR, put a Nikon 2.5x projective eyepiece in the ocular. Then add more m42 spacers above with another helicoid and an appropriate m42 adapter for your camera. Add/remove spacers and adjust the helicoid until the image in the camera is in razor-sharp focus.
Typically the 2.5x is good for full frame and works on aps-c with a bit of cropping.
Image
The end result looks awfully tall, but it doesn't seem to have any problem with being tilted, and the vibrations aren't too bad.

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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Wed May 15, 2019 12:24 pm 
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The focal length for a given lens/optical path is a function of the distance from the lens to the sensor. You can reduce the massive length of tube if you use what are called 'extension tubes', which are little spacers with electrical contacts to preserve autofocus/aperture adjustment/IBIS/etc. They will also allow you to have a way larger image on the sensor with way less vignetting. Some people call extension tubes the poor man's macro (and they are very very cheap, given camera equipment costs).

The distance to the sensor issue is a big part of why lenses for DSLRs are so huge (vs mirrorless interchangeable lens cameras. Canon and Nikon have both caught onto the major advantages to having no SLR mirror, especially since perfect composition of a shot with a optical viewfinder is kind of pointless today since everything is cropped digitally vs film)... but that's a tangent.

To give you an idea of what size of image you can get on the sensor, the linked picture was taken using an extension tube and a 14-45 mm (28-90mm equivalent for full frame) lens on a micro 4/3's camera and I have applied absolutely no crop. There was probably 20-30 cm distance between the front of the lens and the stone. Also, if I stop stop down completely (I think f/5.6), I can have both the table and the pavillion facets in focus simultaneously, while filling the entire sensor with a decent sized stone, and that kind of distance. I didn't use any special lighting for the photo either, The camera is far enough away so that there is no real issue with lens shadow. All that is somewhat an aside, but does speak to the advantages that increasing the distance to the lens with extension tubes would have for setting up microscopy shots as well.

https://i.imgur.com/V01m21p.jpg


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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Wed May 15, 2019 1:14 pm 
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That approach isn't particularly suitable for a microscope setup. You can certainly just suspend the camera higher above the trinocular port with no intervening optics, and you can get a sufficiently large image to cover your sensor that way. If someone wants to take that path they can just skip the ocular and eyepiece and put their camera directly on the tube. However it will not be parfocal with the eyepieces (meaning you have to severely refocus every time you want to take a shot). By doing that you're also pushing the optics into a configurarion they're not optimized for (essentially changing the tube length a lot) and with a microscope that is probably going to degrade the image noticeably. Overall, definitely not my recommendation--stereo microscopes are already not ideal for photography, but their convenience and ease of use compensates a lot. Making one more of a pain to use for photography kind of defeats the purpose, even aside from what it might do to image quality.

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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Wed May 15, 2019 10:46 pm 
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I'm not sure what pain you are speaking of. One o the wonders of a digital camera the ability to automatically control focus/aperture/iso sensitivity without intervention. If you are using a continuous zoom stereo microscope (where the intervening distance between the ocular and objective is used to control magnification), there is absolutely no compensation for the changing parfocal/image-forming point on the trinoc optical path vs your eyepieces. On a fancy rig with an airtable maybe, there would be servo/steppers controlling the (relative) tube lengths which compensate for this... I am assuming instead you are manually correcting this every time you take a shot. This is as opposed to allowing (at bare minimum) continuous autofocus, or (at best) electronic control of focus by attaching the camera to a computer which essentially gives you control-by-wire stepper motors for tube length adjustment, and (lens-dependant) increase magnification of the field somewhat for a photo without having to set up your field all over again. But I really don't know what to tell you if you think that this is going to significantly reduce image quality. The FWHM/PSF for a decent lens' resolving power isn't going to be the issue with the kind of microscopy we're doing. (And assuming you are in well-funded academia... you really do have to apply the same critical mind to the claimed limitations by commision/bonus-hungry sales reps from companies like Zeiss as you do while doing a literature review.)


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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Thu May 16, 2019 12:39 am 
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I'm a bit confused.
You can certainly control iso/shutter speed etc with a digital camera attached to a microscope. But autofocus/aperture would require you to have some intervening optics between the camera and the microscope, which is a whole different can of worms. There may be some good configuration for that on an SZ7, but I haven't run into it.
Zooming stereos don't control zoom by moving the main objectives, zooming in adjusts magnification by moving of two sets of internal lenses relative to one another, and is set up to avoid any change to the working distance. This is how it maintains parfocality as it zooms, both in the eyepieces and in the trinocular port. If the scope is set up properly you don't need to refocus at all going from 1x to 7x, and again don't have to refocus when you switch the light path to the camera. If you place the camera body high enough above the trinocular port to fill aps-C with no intervening optics the microscope would have to be cranked down (ie, the front objectives moved physically closer to the subject) to get it in focus--you are changing the working distance. I have had microscopes in that situation before, and it is not great.
Low-magnfication, long working-distance macro work is fairly different from microscopy.
Do you have a microscope on hand? If so, I am kind of curious what type.

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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Thu May 16, 2019 6:43 pm 
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I wrote a pretty long reply, but I lost it to my power going out unexpectedly.

Image

Your correct about the stable focus between the trinoc port and the view from the eyepieces when zooming. I believe we were describing how zoom works using an identical optical path, aside from my trinoc snafu. Your's conceptually groups the lens elements the way the design intended; mine was grouping them in convoluted (no pun intended, lol) way due to my opposite regarding the trinoc.

If you label the lenses in (first configuration in the) diagram, starting at the bottom as a1, and proceed upwards with a2, a3, etc... Then you explained a2-a4 as working by adjusting the location of a3 between the fixed a2 and a4. When a3 is closer to a2, it essentially diverts the light from the periphery of the field outward enough that it falls outside of the path of a4, thereby magnifying the field. This is the (correct) description I believe you were giving.

Because I thought that the trinocular port was beamsplit between a3 and a4, (instead of above the a2-a4 lens system), I was conceptualizing an a3-to-trinoc as essentially being equivalent to a variable tube length.

--------

However, all this aside... I don't know if the microscopy companies recommend different things when they sell the scopes for dissecting vs gemology (us biologists love the B&L stereozooms for microsurgical stuff w mice), but I have never ever seen a setup which has the trinoc forming an image on a dSLR sensor without intervening optics. The official approach is to use what they call a special 'relay lens' so you don't have to deal with a giant tower on the trinoc (especially since vibration from movement is unavoidable for dissection/surgery).

My recommendation was based on the fact that the quintessential thing that makes it a 'relay lens' is the fact that it actually has an increased distance from the sensor compared to a normal lens... Hence my recommendation that one can achieve the same result as 'recommended solution' (at least in biology) by simply using extension tubes to do the same thing.

And to answer your question about scopes I've used, I have spent most of my time on B&L stereozooms without a trinoc (hence my mixup), and on something like the Zeiss LSM880... which is a laser scanning multiphoton fluorescence rig.


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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Thu May 16, 2019 8:17 pm 
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Generally there aren't different recommendations for gemology vs biology (or really any recommendations for gemology, aside from the base). This setup does use both extension tubes (just without the electric continuity since there is nothing to connect to--either way it's an empty metal tube) and a relay lens (in this case the relay lens is the same eyepiece that you'd use in the ocular). It is optically the same as an original B&L mount for a 35mm camera, just rendered in an easy DIY solution with easier-to-get components, and made compatible with the more widely-available style of sz7 trinocular.
This is what a SZ7 looks like with a polaroid camera mounted (all B&L original parts):
Image
The mount being very tall is pretty common when putting a dslr on a trinocular stereo microscope (or even a compound microscope in many cases) across most makers. Some models use beamsplitters with an elbowed adapter so some of the distance is horizontal, though the total length is still considerable if you add it up. Others might have some other optics in the light path to make the required distance shorter, but look at the below examples:
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[yes, LMscope sells third party adapters but if you look at a Leica adapter diagram the length is the same as their original parts]
Image
Of course on an inverted microscope like a Zeiss LSM the entire light path can be configured differently so it isn't dangling up in space.

That all being said, though it looks ponderously tall the setup for the SZ7 is quite solid and with a dslr with efcs and remote shooting I don't think it will have excessive problems with vibration. I haven't gotten to do extensive testing yet since it's at my dad's place and he hasn't hooked it up to his PC yet for remote shooting. Still, early test shots were good.

On the image quality front, some things you can get away with pushing out of spec, others much less so. This isn't exactly the same thing, but Charles Krebs has a great demonstration here of how pushing a photo eyepiece a bit out of spec can cause fairly noticeable issues with the image quality: http://www.krebsmicro.com/NFK_lowermag/index.html

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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Fri May 17, 2019 9:03 pm 
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The relay lens refers to a difference piece of hardware than the ocular. This is the configuration that is referred to when poeple talk about a relay lens

Image

Also, if talking about pushing things out of spec... that's precisely what happens when you use a eyepiece intended for an observer and no relay optics. Quoting from a great introduction article talking about the very configuration you are using http://www.quekett.org/resources/advanced-photomicrography:

"Many microscope adapters consist of a simple tube without relay optics; it is inappropriate to use an eyepiece designed for visual use with these adapters as these are designed to project an image at infinity (and brought to a focus by the lens of the eye). To project a real image onto the camera sensor, refocusing will be necessary which introduces spherical aberration, and degrades the image. The correct solution with these simple tube adapters is to use a specially designed projection eyepiece."


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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Fri May 17, 2019 11:40 pm 
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As far as I can tell the B&L setup was designed to be used with a normal ocular (which wasn't unheard of either--the cycloptic's photo port is also designed that way), and you get good results in this configuration. I say as far as I can tell because documentation is a bit spottily available given the age of the system and the unusual use case--it does line up with the components that came with the first sz7 photo adapter I bought.. I did a preliminary test with using a projective photo eyepiece instead while setting it up (the Nikon 2.5x is a good option because it doesn't apply any significant corrections to the image--as close to universal as you can get for a stereo, and is good for eg the olympus szh) but it didn't produce superior results in basic testing (though this may benefit from further examination in the future). So while I don't know the optical specifics I believe this is operating as b&l designed it to.

Using a photo eyepiece with a separate relay lens is another popular setup (I have a trinocular Leitz that is set up that way, and Leica's stereos take a similar approach--it's also often done ad-hoc by hobbyists, combining a higher-magnification projective and a 50mm set to infinity to get you an image circle well-sized for aps-c). This definitely doesn't get you a shorter stack, though. Once we're into experimental territory there is a lot of room to explore, and plenty of components one could try.

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 Post subject: Re: Easy diy dslr adapter for bausch and lomb stereozoom 7
PostPosted: Sun May 26, 2019 11:50 pm 
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I finally got to sit down and do some serious testing with this, and I'm changing my recommendation. Using a Nikon 2.5x projective eyepiece gets much better results. You'll still use the b&l eyepiece to find the right positioning for the eye tube, but then you'd take it out and put in the 2.5x. This actually requires a bit more extension but it's worth it--images are much brighter and sharper.
Plus side, there doesn't seem to be an excessive issue with vibration. You need to not bump the table during a stack but nothing too severe.
I also have a Kodak MDS120 universal adapter coming in--there has been a report of good results with this lens, so I'll give it a try as well.

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