what camera lens to use for Parphocal setup?

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clipi
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what camera lens to use for Parphocal setup?

#1 Post by clipi » Mon Aug 26, 2019 5:40 pm

I am adding a Canon 200D camera to my leitz laborlux microscope. I want to use a parphocal setup
Phototube + 10x periplan eyepiece and camara with corresponding lens on top.
I have seem similar setups in this forum but I am not sure which will be the best lens to use. A 50mm or 40mm pancake lens seem
popular altough I read that a more equivalent to human eye would be a 22mm lens.
I would appreciate any advice or information on the best parphocal setup.
Thanks so much

Hobbyst46
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Re: what camera lens to use for Parphocal setup?

#2 Post by Hobbyst46 » Mon Aug 26, 2019 5:47 pm

I think that the appropriate camera lens would be a prime 40mm, for the APS-C sensor of the Canon 200D camera.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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75RR
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Re: what camera lens to use for Parphocal setup?

#3 Post by 75RR » Mon Aug 26, 2019 7:04 pm

From your description it would seem that you are looking into an Afocal setup.

http://www.krebsmicro.com/pdf/trinoc_a3.pdf

+ link to main site: http://www.krebsmicro.com/

Parfocal refers to making the phototube eyepiece simultaneously in focus with the binocular eyepieces.
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Olympus E-P2 (Micro Four Thirds Camera)

MicroBob
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Re: what camera lens to use for Parphocal setup?

#4 Post by MicroBob » Mon Aug 26, 2019 7:16 pm

40mm is right for normal field sizes like 18mm or so. For something really wide like 28mm a shorter focal length might be better.
A proven lens for this purpose is the Pentax M 40mm 2,8 pancake from the late 1970s.
The idea is that the rectangular sensor just fits into the roung field, no black corners, not too much uncovered field area. The exit pupil of the eyepiece should be in the same point as the rntrance pupil of the camera lens. This rules out 35mm SLR lenses - they are built too long.
Wit 22mm focal lenght on APS-C you would have a normal wide angle lens. This would give you a circular image of the field ald a lot of black border in the corners of the image.

Bob

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Re: what camera lens to use for Parphocal setup?

#5 Post by Scarodactyl » Tue Aug 27, 2019 2:12 am

The EF 40mm pancake works great from my handheld testing.
Its coverage is very close to ideal, almost perfectly fit to the image circle (canon picture here overlaid on a cell phone pic showing the full FoV)
Image

If you want to directly hook it on you can get this 40mm adapter from RAFcamera https://rover.ebay.com/rover/0/0/0?mpre ... 2384138340
And a male/male adapter https://rover.ebay.com/rover/0/0/0?mpre ... 0457460785
To attach it by the filter threads it directly to the 40mm trinoc.
I am still waiting on the male/male adapter to finally hook mine up, but it looks like it should work well. Maybe not as ideal as suspending it above the trinoc port without a hard connection but with a canon vibrations aren't too bad.

clipi
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Re: what camera lens to use for Parphocal setup?

#6 Post by clipi » Thu Aug 29, 2019 9:26 pm

Thanks so much for information guys very helpful.
Is it posible to us a variable lens from 15 to 45mm?

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Re: what camera lens to use for Parphocal setup?

#7 Post by Hobbyst46 » Thu Aug 29, 2019 10:15 pm

clipi wrote:Thanks so much for information guys very helpful.
Is it posible to us a variable lens from 15 to 45mm?
Yes. Initially, set the zoom to the correct focal length for your optics. Focus at infinity. Secure the focusing ring and zoom ring from changes by wrapping cellotape around. Thats it. Possibly the result will be somewhat less nice than using a fast prime lens, the zoom is usually slower, but is the difference significant ? I do not know.
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Re: what camera lens to use for Parphocal setup?

#8 Post by MicroBob » Fri Aug 30, 2019 10:28 am

clipi wrote:Is it posible to us a variable lens from 15 to 45mm?
If you already have it I would give it a try. The entrance pupil will probably lie quite deep in the barrel so it might not match with the exit pupil of the eyepiece too well. When matched perfectly the image just becomes darker when you stop the camera lens down. When the match is not so good you will get dark corners. This is the reason to prefer pancake lenses. There is no need for an especially fast camera lens here. It is good to test the camera setup with high power microscope objectives too. They have the effect that them make imperfections in the camera lens visible. Many zoom lenses use asphericla lenses that are made from plastics. They can give strange rings in the image but only really show when used with high power objectives. You might google for "coolpix rings", as this was the first camera where this phenomenon was detected.

Practice beats theory though if it works - it works.

Bob

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Re: what camera lens to use for Parphocal setup?

#9 Post by zzffnn » Fri Aug 30, 2019 1:15 pm

40mm lens on 1.6x crop factor Canon APSC sensor is about right, which is almost the same as 30mm lens for 2x crop micro four thirds sensor.

Some external zoom lens may not stay at 40mm, under the weight of an afocal camera, unless you tape the lens barrel. Give it a try and see it that works.

20-25mm lens on 2x crop micro four thirds sensor is close to human eye, as I remember. But human eye sees a circle from eyepiece, while camera sensor records a rectangular view field. So they work differently.

clipi
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Re: what camera lens to use for Parphocal setup?

#10 Post by clipi » Mon Sep 02, 2019 9:29 pm

I have seen a Leitz phototube which uses a 0.32x relay lens. So will a setup with camera without lens+0,32x relay lens+10x eyepiece be equivalent to
a Camera with 40mm+10x eyepiece?
What about using an eyepiece with a widere field of view like a GF 10x/20?

Thanks.

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Re: what camera lens to use for Parphocal setup?

#11 Post by Scarodactyl » Mon Sep 02, 2019 11:40 pm

clipi wrote:
Mon Sep 02, 2019 9:29 pm
I have seen a Leitz phototube which uses a 0.32x relay lens. So will a setup with camera without lens+0,32x relay lens+10x eyepiece be equivalent to
a Camera with 40mm+10x eyepiece?
Unfortunately not, the 0.32x relay lens gives a lot more cropping than a 40mm lens (did someone say it was a ~60mm lens at some point? I'm not sure, haven't measured it).
As posted above, this is the image given by a 40mm canon pancake lens focused to infinity on aps-c overlaid onto a cell phone image of the full FoV (I accidentally switched to one of the UV filters on the cell phone pic, hence the yellowness):
Image
And here is the Leitz 0.32x lens adapted onto the same canon camera and focused to infinity:
Image
IMO, image quality seems to be just fine, but it's longer focal length and the cropping is pretty rough on aps-c.

clipi
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Re: what camera lens to use for Parphocal setup?

#12 Post by clipi » Tue Sep 03, 2019 3:43 am

Thanks Sarodactyl, I guess that a 0.5x or 0.75x relay lens will be closer to a 40mm lens am I correct?



Also if you have this phototubes set, could you please tell me the length of the long tube with the two screws?
I want to make a 3d printable version of the set.

Thanks
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Scarodactyl
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Re: what camera lens to use for Parphocal setup?

#13 Post by Scarodactyl » Tue Sep 03, 2019 4:00 am

I actually don't have that tube (mine came with a more elaborate shuttered setup). I am not sure that the length of it is that critical, as the image doesn't seem to change with distance when the lens is set to infinity (until you start to get vignetting when it is too far away). I might be wrong on that, as I haven't experimented with it extensively (edit: today I held the camera with lens lens loose above the eyepiece, set live view to 5x zoom on a spot towards the edge and slowly moved the camera up and down. Nothing about the image seemed to change at all. I think it's safe to mount it at whatever distance is comfortable as long as it isn't high enough to vignette).
A 40mm is probably closer to 1.6x.

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Re: what camera lens to use for Parphocal setup?

#14 Post by Scarodactyl » Wed Sep 04, 2019 1:35 am

Just as a quick update, here is what I just got set up:
Image
This is a normal Leitz tl 160mm camera adapter with a 10x/18 periplan eyepiece in it. Clamped onto the outside (40mm) is this rafcamera adapter ( https://www.ebay.com/itm/40mm-to-M52x1- ... 2384134164 ) and a m52 male to m52 male adapter (https://www.ebay.com/itm/Male-52mm-52mm ... 0457460785) so it will screw right onto the filter threads of the Canon 40mm pancake.
However, the Leitz camera adapter is also easy to recreate using a 38mm to m42 adapter, standard m42 spacers and a B&L stereozoom microscope ocular scavenged from a broken unit to hold the eyepiece (the ocular press fits nicely into the spacers--it takes some tweaking it get it properly aligned but you only would need to do that once):
Image
Image
Image
Since the 38mm adapter is just held in place with a set screw it's easy to do fine focusing by raising and lowering it before tightening the set screw. Then you just need more m42 spacers and an m42 adapter to the filter thread of whatever camera lens you want to use.
That said, 3D printing the adapter would at the very least look nicer, and of course it's a lot nicer to be able to just drop it into position and tighten the set screw rather than having to raise or lower it for focusing.

clipi
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Re: what camera lens to use for Parphocal setup?

#15 Post by clipi » Thu Sep 05, 2019 11:00 am

Thanks so much for sharing!
I 3d modeled some phototube which you can see here. I will try to do something similar to your setup
One of the tubes fit the 38mm trinocular and I made one to replace the trino or for those which dont have one

One question, I have a 50mm pancake lens... how will the resulting image be in relation to 40 mm pancake??

Thanks again!!
Screen Shot 09-05-19 at 08.34 AM.PNG
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MicroBob
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Re: what camera lens to use for Parphocal setup?

#16 Post by MicroBob » Thu Sep 05, 2019 11:15 am

clipi wrote:
Thu Sep 05, 2019 11:00 am
One question, I have a 50mm pancake lens... how will the resulting image be in relation to 40 mm pancake??
You will zoom in further into the image circle and a bigger part of the image will be cut off. This also depends on the size of the image circle. If it is small, the 50mm camera lens might be just right.

clipi
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Re: what camera lens to use for Parphocal setup?

#17 Post by clipi » Wed Sep 25, 2019 2:34 pm

Hello again..

I just got an Olympus zuiko 50 mm pancake.
I was wondering what are typical values used for microphotography of Depth of field and aperture?
do I have to set the lens to infinity when used with and eyepiece attached to the filter thread?
Thanks

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Re: what camera lens to use for Parphocal setup?

#18 Post by Scarodactyl » Wed Sep 25, 2019 6:51 pm

I'd leave the lens wide open. It does need to be set to infinity. You have some options for adapting it. Using the filter threads to adapt on a 40mm clamp might be easiest, yours I think has a 49mm thread but it should be possible to adapt woth a stepup filter and the parts I linked in my earlier post.

clipi
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Re: what camera lens to use for Parphocal setup?

#19 Post by clipi » Thu Sep 26, 2019 10:57 pm

I will try a 49 to 28 mm adapter for the eyepice to the filter thread and see what happens.
Thanks so much for your help!

Scarodactyl
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Re: what camera lens to use for Parphocal setup?

#20 Post by Scarodactyl » Sat Sep 28, 2019 3:44 am

Scarodactyl wrote:
Wed Sep 04, 2019 1:35 am
Just as a quick update, here is what I just got set up:
Image
Just a quick update, I finally had a chance to test position by stopping down the pancake lens. The Raf adapter has a small lip that positions the lens just a little bit above of the ideal point--it was easy enough to file off, though I am not sure it's necessary or that it will affect performance noticeably.

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