Is a Zeiss C8x eyepiece useful for afocal or focal photomicrography?

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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Hobbyst46
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Is a Zeiss C8x eyepiece useful for afocal or focal photomicrography?

#1 Post by Hobbyst46 » Sun Jan 28, 2018 5:02 pm

Hello all.
I am experimenting with fitting a mirrorless APS-C camera to my new trinocular head on the Zeiss GFL microscope.
For recording afocally, using a viewing eyepiece and either a 15-45mm zoom lens or a (manual) 50mm 1:1.7 prime lens.
The objectives are Olympus Splan 10x0.30, Zeiss 40x0.75 neofluar, 63x1.4 Planapo.

My test specimen is an old Zeiss stage micrometer, 0.01mm/tick, bright scale marks on black background. Also a slide of green algea.

So far I have tried a Zeiss KPL 10x, about 7mm eyepoint. Obtained excellent parfocality with the eyepieces, and the only issue is a visible though small pincushion distortion, especially at the high mags. In addition, The manual camera lens aperture must be below about 4 for the image to feel the screen.

Having read a lot about fitting a camera to a microscope, I had the impression that a 8X eyepiece may be better than the 10x,
so ordered a Zeiss KPL 8x.

But, I am also being offered an inexpensive Zeiss C8X eyepiece. I cannot find out if this is a photo projection eyepiece, a centering eyepiece or what? Is it compensating?
Can anyone tell if a Zeiss C8x eyepiece is useful for afocal, or perhaps focal photomicrography?
Thanks in advance.

Charles
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Joined: Mon Mar 02, 2015 11:55 pm

Re: Is a Zeiss C8x eyepiece useful for afocal or focal photomicrography?

#2 Post by Charles » Sun Jan 28, 2018 5:32 pm

Here is a link to the older Zeiss Optical Systems catalog. In the eyepiece section it states the C eyepiece is only suitable for low NA objectives.
http://www.science-info.net/docs/zeiss/

MicroBob
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Re: Is a Zeiss C8x eyepiece useful for afocal or focal photomicrography?

#3 Post by MicroBob » Sun Jan 28, 2018 8:05 pm

The "C" eyepieces are compensating non planar eyepieces with small field of view and little eye relief. They can also be used for strong objectives as all Zeiss Standard objectives are calculated for the same compensating factor. This was a big invention at the time. They don't make use of your Planapos planar image though. With the little eye relief it is difficult to find a camera lens where the lens's entrance pupil is close enough to the lens front. You already have this problem when you have to open the cameras aperture to avoid vignetting.

So this is probably one of the least attractive eyepieces for photo use.

The entrance pupil of both your camera lenses sit relatively deep in the lens body, so you would need a more modern eyepiece that permits the use of glasses.
For an APS-C camera a 40mm pancake lens is perfect. There is a Pentax 40mm 1:2,8 from about 1980 that fits the bill. Here you might get along with an eyepiece with medium eye relief.

Bob

MicroBob
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Re: Is a Zeiss C8x eyepiece useful for afocal or focal photomicrography?

#4 Post by MicroBob » Sun Jan 28, 2018 8:39 pm

I forgot two things:
object micrometer is perfect as a test target - use it with cover slip.
For old "keyhole" eyepieces a smartphone can be the perfect fit optically.

Hobbyst46
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Re: Is a Zeiss C8x eyepiece useful for afocal or focal photomicrography?

#5 Post by Hobbyst46 » Sun Jan 28, 2018 9:37 pm

Charles and MicroBob - thanks.

I think I will skip the C8X then.

What I now have for the photo tube, in addition to the older style Zeiss 10x, is a Zeiss 10x W (20mm eyepoint) that is visually delaminated so I hesitate to use it, and an Olympus WHK 10x18 that is not exactly parfocal with the viewing eyepieces.

And on the other hand, the camera is a Canon EOS-M10, with a 15-45mm zoom lens, the front of which is very close to the mechanical front; and a 50mm Minolta MD lens, where as you say the glass front is deeper inside. I just have to be careful not to scratch it with the photo eyepiece - I add a foam ring.

There is a modern 40mm 2.8, EF pancake lens, 52mm filter thread for the Canon EOS cameras. When budget permits, I can consider it. Since my phototube adapter is now based on 49mm threads, this lens will necessitate new or additional step-down adapter rings as well.

But with a 8x photo eyepiece and the 50mm Minolta lens, the total relay magnification is 400x, same as 10x eyepiece and 40mm camera lens, so perhaps the performance will not be very different.

Bob, also thanks for pointing to me to use a coverslip on the stage micrometer - it is made of steel and I just did not think of a cover...

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