Two afocal photomicrography setups (now three)

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Pau
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Post by Pau »

Another setup, optically identical to my fist posted one but more compact and easy to use: precentered and easily rotatable (and of course also more prone to camera induced vibrations)
The components, from left to right:
- Zeiss camera adapter. It's a part of old camera couplers, not difficult to find used. It fits over the 25mm microscope tube
- High eyepoint eyepiece
- Zeiss Standard dovetail to M49x0.75 adapter, a rare Zeiss part but Rafcamera can make it
- Empty M49x0.75 filter ring to avoid big eyepieces hitting the lens
- Olympus OM 50/1.8 with a OM to EOS adapter
Image


The components mounted on the Zeiss trinocular camera port

Image

Image
Pau

Adam Long
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Re: Two afocal photomicrography setups (now three)

Post by Adam Long »

Another Zeiss afocal setup using parts from the MC63a camera:
IMG_4478.jpg
There are usually MC63a cameras on ebay and usually cheaper than the 2.5x adapter Pau is using.
AL-0451s.jpeg
It splits into these components:
AL-0452s.jpeg
The bottom conical part gives a solid factory machined and adjustable mount to the trinoc tube, to which I just add the camera bayonet to make a flat platform on which the camera lens rests (under it's own weight only) on a small step-up ring. I was initially inclined to glue it but the slight lateral freedom of movement can be useful to reduce reflections.
AL-0455s.jpeg
Eyepiece is the Zeiss S-KPL 10x/20. I mainly use the Sony A7 in APS-C mode with the Sony/Zeiss 35mm which gives a nice crop of the full field with no corner shading. I have a Voigtlander 65mm which should be ideal but the front element is too recessed to access the exit pupil.

Pau, are you still using the Zeiss 63mm lens? I tried the one in this camera and results were not encouraging, but perhaps I should try harder. Appears to be a very simple lens, two elements at most. I also have the 0.8x 4x5 adapter but have not experimented with it.

Pau
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Re: Two afocal photomicrography setups (now three)

Post by Pau »

Hi Adam,
I've seen lots of these MC63 adapters for sale and I've been tempted to buy one just by curiosity. Like you I guess that the 63mm lens inside might be the same or closely related with the one in my SLR adapter, nice to see it dismounted and adapted. Which is the original position of the 63mm lens?
I tried the one in this camera and results were not encouraging, but perhaps I should try harder. Appears to be a very simple lens, two elements at most.
My adapter if used alone on the camera as taking lens is a really poor one but as converging lens at afocal it works very well, no important IQ differences with my other afocal arrangements for APSC:
- Zeiss 63mm + Leitz Periplan 6.3X vs Pentax MC 40mm 2.8 + Leitz Periplan 10X --with Leitz objectives
- Zeiss 63mm + Zeiss KPL 8X vs Pentax MC 40mm 2.8 + Zeiss S-KPL 10X (different magnification aside) --with Zeiss objectives

What are the issues you're experimenting?
Pau

Adam Long
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Re: Two afocal photomicrography setups (now three)

Post by Adam Long »

Which is the original position of the 63mm lens?
My best efforts in measuring come up with the following:

The 63mm lens is in a holder 6mm thick. The actual lens is thicker and protrudes slightly.

The camera allows this to be positioned a minimum of about 20mm above the eyepiece (20.2mm to the mount, I didn't attempt to measure the lens protrustion). I assume this matches the eyepoint.

From the other side of the lens to the film rails is about 65mm - so the lens is focused somewhat closer than infinity.

The lens is held in position within the mounting threads of the Prontor Magnetic shutter, which means it can't immediately be used without the shutter. There is a datasheet for the shutter here which has thread specs (M29.5 x 0.5F) and control voltages which suggests a controller might not be a trivial build: https://web.archive.org/web/20190727123 ... tter_0.pdf
However mounting the lens centrally and securely within the main body should not be too difficult.
What are the issues you're experimenting?
Having initially assessed the optics were poor, I'm now thinking this is more likely operator error. I found the following in Hartley's Microscopy which suggests there might be advantages to the Zeiss 63mm over my existing setup:
As the diameter of the microscope eyepiece is very small, the camera lens is working at a very restricted f ratio... the simpler the lens the less internal reflection will occur... a simple achromatic lens is better than a complex 100mm telephoto; as it is working at about f/30 it has no scope for displaying optical defects
Assuming this remains the case for today's high resolution sensors it seems worth a try at least. Although the results with my 35mm lens are very good there occasional issues with reflections. And it might be nice to use the Zeiss eyepiece I have with the photo frame graticule.

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Re: Two afocal photomicrography setups (now three)

Post by Adam Long »

PS, found this, so the shutter might be worth experimenting with a simple 3v to hold open:
I have found for the Ilex shutters, for slower speeds, the 10x pulse requirement can be ignored, it's meant to get the shutter to snap open quickly by overcoming the magnetice hysterisis of the coil. For b and t one can use the lower voltage, or slightly more, the actual voltage needs to be determined based on your requirements for responsiveness.

Scarodactyl
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Re: Two afocal photomicrography setups (now three)

Post by Scarodactyl »

There are more permanent solutions for shutters too. You're never going to need it even if it's nifty.

I tried an afocal setup on my universal using a 40mm pancake on my canon aps-c dslr, just with boring rafcamera adapters. It worked but the results with a viewing eyepiece were underwhelming, though whether it was the eyepiece (tried a few normal viewing eyepieces only), the objectives (epiplan achromats) or the lens I cannot say (but probably the first two together). I ended up doing the hybrid eyepiece trick (per Rolf Vossen) by putting the lenses from a 10x eyepiece onto a longer 8x eyepiece barrel to make a projective eyepiece and that worked at least as well.

Adam Long
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Re: Two afocal photomicrography setups (now three)

Post by Adam Long »

There are more permanent solutions for shutters too. You're never going to need it even if it's nifty.
Agreed. I had a go at using a low voltage to hold the shutter open but was unable to get so much as a twitch. So I opened it up. Unlike the clockwork nightmare of a traditional Copal shutter, there is almost nothing but a solenoid and the shutter blades. You can either just use the back plate of the shutter and discard the rest, or just lift out the shutter blades and reassemble (which gives a bit more baffling to the lens). Either way it's a quick job and results in the lens held securely in the correct position as Zeiss intended.

The rest of the camera can then be reassembled although it's probably best to remove the meter and half-mirror inserts and blank off the holes. That leaves you with attaching a camera body. The camera bit is I believe based on a Contax 137, by checking flange - focal plane distances and checking with a micrometer I was able to choose an appropriately-sized Sony EF adaptor and had a working rig. For long-term use you could glue the camera's bayonet to the adaptor.

Results are very good, no quality issues obvious and not surprisingly better than the C-mount adapter (visible on my Universal in photo above). However the setup ends up being quite a bit bigger and heavier than my previous method, with the only advantage being the longer focal length. Time will tell whether I feel a need for the tighter crop, but I had some fun fiddling and it's definitely a simple solution delivering good results. Might be interesting to compare the S-KPL vs KPL and CPL if I get chance.

Adam Long
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Re: Two afocal photomicrography setups (now three)

Post by Adam Long »

Photo of this setup below. I've been using it quite a bit, more on the Universal where it seems a bit less top heavy. Ideally it would be worth replacing the metering inserts with some sort of plug.
IMG_4529.jpg

dragonblade
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Re: Two afocal photomicrography setups (now three)

Post by dragonblade »

I admit I'm rather envious of these afocal trinocular setups. I just have to make do with a modest monocular scope.

Pau, I'm intrigued by the empty M49x0.75 filter ring. Could you explain how it prevents the camera lens from hitting the eyepiece? I would have thought that the eyepiece would be a smaller diameter than the filter ring and could pass through it if one wasn't careful.

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Re: Two afocal photomicrography setups (now three)

Post by Pau »

dragonblade wrote:
Sun Dec 12, 2021 4:09 am
...
Pau, I'm intrigued by the empty M49x0.75 filter ring. Could you explain how it prevents the camera lens from hitting the eyepiece? I would have thought that the eyepiece would be a smaller diameter than the filter ring and could pass through it if one wasn't careful.
Yes, the eyepiece has smaller diameter than the filter ring, which function is just as short extension tube: if you look at the chromed Zeiss adapter (second of my pictures in this page) some eyepieces like the one pictured protrude past its level.
If the camera lens front lens surface is not enough recessed the eyepiece can hit and damage it. This happens with the eyepiece and lens pictured.
With smaller eyepieces or with lenses with more recessed frontal element this ring is not necessary, for example with the Pentax 2.8/40mm or with the Canon Compact Macro 2.5/50mm I don't use it.
Pau

dragonblade
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Re: Two afocal photomicrography setups (now three)

Post by dragonblade »

A very nice afocal setup. And compact too.

That's interesting that you're using an Olympus lens with a Canon EF adapter. I know that with the EF mount, there is a considerable distance between the lens and the focal plane which makes it rather challenging to adapt lenses successfully. A lot of the old manual film lenses like Canon FD lenses cannot be focused to infinity. Though I'm guessing the Olympus lenses may be an exception to this?

Pau
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Re: Two afocal photomicrography setups (now three)

Post by Pau »

The Flange Focal Distance (FFD) of the Canon EF mount is 44mm, shorter than most other SLRs mounts, being Canon FD a notable exception. At the wiki https://en.wikipedia.org/wiki/Flange_focal_distance you have a table with these data.
This allows infinite focus with lensless adapters in many cases, for example I use Olympus OM, Pentax K and and Contax/Yashica lenses on my EOS camera
Pau

blekenbleu
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Re: Two afocal photomicrography setups (now three)

Post by blekenbleu »

My AO Cycloptic lacks a photo tube, but its body tubes (for eyepieces) are a little less than 30mm o.d.,
while a telescope adapter advertised as 1.25 inch turns out to be slightly more than 30mm i.d.:
Image
https://www.amazon.com/dp/B082HC7DYY

.. with that difference reconciled using a strip of 0.5" wide .032" brass shim:
Image

Then, adding a male T2 - M42 coupler and (for my 40mm lens) a 52-42mm step-down ring yielded this afocal configuration:
Image

Less than 40mm focal length would be more nearly ideal for APS-C sensors and 10X oculars.
Calipers confirm that most of my microscope body tubes have diameters for which this would work.
Last edited by blekenbleu on Mon Jan 15, 2024 9:19 am, edited 1 time in total.
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

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Re: Two afocal photomicrography setups (now three)

Post by Pau »

blekenbleu, this is a nice afocal adaptation for 30mm+ eyepiece tubes! Thanks for posting it.
blekenbleu wrote:
Tue May 24, 2022 3:18 pm
Less than 40mm focal length would be more nearly ideal for APS-C sensors and 10X oculars.
Calipers confirm that most of my microscope body tubes have diameters for which this would work.
This depends more of the Field Number of the eyepiece and of the quality of the microscope image periphery than of the tube diameter.
40mm over 10X eyepiece produces about 1.6X secondary magnification, the usual recommendation for APSC.

For modern high end wide field microscopes, lower magnification/wider field would be nicer, no idea about your classic AO stereo. With my also old and well regarded Wild M5Apo I find this 1.6X adequate.

Another possible issue is that most SLR lenses shorter than 40mm are wide angle designs with more image distortion.
Pau

blekenbleu
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Re: Two afocal photomicrography setups (now three)

Post by blekenbleu »

Pau wrote:
Wed May 25, 2022 9:20 am
blekenbleu, this is a nice afocal adaptation for 30mm+ eyepiece tubes! Thanks for posting it.
Thanks, I thought someone might have already posted it...
My traditional clamp for approx 25mm o.d. eyepiece tubes works only for my AO monocular head,
while this (1.25" == 31.75mm) clamp happens to accomodate more modern microscope eyepiece tubes.
I have yet to understand an application for 1.25" eyepieces converted to T2, but am grateful such an adapter exists.
blekenbleu wrote:
Tue May 24, 2022 3:18 pm
Less than 40mm focal length would be more nearly ideal for APS-C sensors and 10X oculars.
Calipers confirm that most of my microscope body tubes have diameters for which this would work.
This depends more of the Field Number of the eyepiece and of the quality of the microscope image periphery than of the tube diameter.
40mm over 10X eyepiece produces about 1.6X secondary magnification, the usual recommendation for APSC.
Actually, I did that math wrong;
the matching eyepiece without camera attached shows a 7mm field,
while this 40mm camera lens shows about 5.5mm wide on a 2x3 sensor;
anything wider would probably have vignetting in corners.
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

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