Wild stereo phototubes vs. 50/50 beam splitter and photoport

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jfiresto
Posts: 39
Joined: Sun Nov 18, 2018 4:54 am
Location: Northern Germany

Post by jfiresto »

The older Wild 352873 phototube does that: it essentially provides a third, 30mm eyepiece tube. I have one that came off an M8.

A third eyepiece tube is not really my beer. It requires another lens to get the intermediate image out of the tube, another lens between the microscope and the camera, to degrade the image.

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Post by Scarodactyl »

I have a general question. I have one of the 37mm ID stereo photo tubes, and I didn't want to hacksaw it down for direct projection, tempting as the idea is. Instead I got a Wild 5x stereo eyepiece and am doing afocal using a wild/leitz 0.32x lens above it. I had previously mounted this 0.32x lens on my canon and focused it to infinity to use on a Leitz trinocular head over a periplan eyepiece and it worked quite well (though with excessive cropping onto APS-C, hence picking up a 5x Wild for my next attempt). However, while I am able to get the eyepiece in focus in the trinocular port, mounting the camera above with the 0.32x lens focused at infinity doesn't get the image quite in focus. It actually has to be pushed further from the camera body/focused closer up. Do not all eyepieces focus to infinity?

Pau
Site Admin
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Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Post by Pau »

Scarodactyl wrote:... However, while I am able to get the eyepiece in focus in the trinocular port, mounting the camera above with the 0.32x lens focused at infinity doesn't get the image quite in focus. It actually has to be pushed further from the camera body/focused closer up. Do not all eyepieces focus to infinity?
Is the trinocular tube eyepiece visually parfocal with the binoculars?

AFAIK all visual eyepieces when at their right position make a virtual image (infinite focused) adequate for human vision and also -more or less- for afocal photography

In the other hand, projective photoeyepieces (again at their right position) do project a real image at shorter distance.

Altering the distances both can work the other way quite well, but don't expect the best results

Few points to test:
- check again the infinite focus of the 0.32 lens
- try with a camera lens focused to infinite...or even with phone camera.
Pau

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Post by Scarodactyl »

I have played with it some more, and I think you are right, it must be a photo eyepiece after all. Even when I put it in one of the oculars and focus it it has a relatively close focal distance.
The eyepiece is just marked Wild Heerbrugg 5x/25, and I haven't spotted it in any of my various wild/leica manuals. Maybe it is for thr M5, or an older M3 product?
I will have to do some more testing on it. This is way out of spec, but if it isn't degrading the image much I will probably keep it as is.

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