Reichert Microstar IV afocal setup?

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BrianBurnes
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Joined: Sun May 31, 2020 6:47 am

Reichert Microstar IV afocal setup?

Post by BrianBurnes »

Hi all,

I'm a bit new to microphotography, so please excuse the possibly wrong terminology. I picked up a cheap infinity Microstar IV with a trinocular head a while ago and have been trying to get my camera (Canon EOS 7D) set up to capture images out of the trinocular port.

The original port has an oddly dimensioned dovetail, and even after some extensive digging I cannot find a camera tube that goes with it. I cobbled together a camera tube out of some 3D printed parts, M42 macro extenders and a helicoid to attach my camera instead, and that seems to work. The camera tube so far has no optics - the beam out of the trinocular port goes directly into the sensor. After some reading on this forum I believe that is "direct projection".

The problem is that it even when the camera is parfocal with the eyepieces (fineadjusted with the helicoid), the results seem blurry and have a lot of aberrations - see below (cropped from the middle of the image). This is despite the image being completely sharp through the eyepieces. After some more reading on this forum I think that the eyepieces also do optical correction on top of magnification, and without an eyepiece in the photo tube, aberrations enter the image. A photo eyepiece does not seem to exist for this microscope, and so I think the best solution here may be what I think is an afocal setup, i.e. add a camera lens and suspend an eyepiece in front of it, between the tube lens and the camera lens.

I'm not familiar with this kind of setup, so I have a few questions about it:
- After reading some other posts, a 40mm pancake lens seems to be recommended for an APS-C sensor. I have a Canon 50mm f/1.8 prime lens, would that also work or should I expect issues with that?
- What distance should the eyepiece be from the front of the lens? I'm sure the exact distance depends on lens/eyepiece, but what order of magnitude should I expect? <5mm? Several cm? I can 3D print movable eyepiece holders but it would be good to know the potential travel of the eyepiece.



Image

Ichthyophthirius
Posts: 1152
Joined: Thu Mar 07, 2013 5:24 am

Re: Reichert Microstar IV afocal setup?

Post by Ichthyophthirius »

BrianBurnes wrote: I'm not familiar with this kind of setup, so I have a few questions about it:
- After reading some other posts, a 40mm pancake lens seems to be recommended for an APS-C sensor. I have a Canon 50mm f/1.8 prime lens, would that also work or should I expect issues with that?
- What distance should the eyepiece be from the front of the lens? I'm sure the exact distance depends on lens/eyepiece, but what order of magnitude should I expect? <5mm? Several cm? I can 3D print movable eyepiece holders but it would be good to know the potential travel of the eyepiece.
Hi Brian,

I'm a bit concerned. Without the eyepiece, the image should still be sharp, just with colour fringes. If it is blury, there could also be other factors at play. Do you use EFSC (from LiveView)? You don't want your camera to go through a shutter movement before taking the image.

A stage micrometer would be ideal to access the performance of our afocal adaptation!

With regard to your questions:
- Optically the Canon 50/1.8 is known to work well; the coverage is not as wide as with a 40 mm so not many people use it; the plastic construction doesn't allow an adaptation that is as solid as with an old mechanical lens but it is usable. Also, the Canon 50/1.8 doesn't have a hard stop at infinity. You need to focus the lens at infinity, then switch off autofocus, maybe secure the setting with tape. The aperture should be fully open.

- In practice, you should try to get a high eyepoint eyepiece as close to the font lens of the camera objective as possible.

A few mm distance are usually best but even with 1 cm it often works. The ideal distance can/has to be found empiracally. Pancake lenses make it easy to have a very small distance. The recessed front lens of the Canon 50/1.8 makes it more difficult.

If you can 3D print, try to make something like this:
https://www.mikroskopie-forum.de/pictur ... 546205.jpg
https://www.mikroskopie-forum.de/pictur ... 999431.jpg
https://www.mikroskopie-forum.de/pictur ... 561464.jpg

The eyepiece goes into the center of the adapter - it gets close to the front lens but doesn't touch it. Make sure you don't scratch the Canon while setting this up.

The camera lens used for afocal should be very clean, as any internal dust in the center of the lens will show in your photographs.

---

A different question is how you would mount the eyepiece to the trinocular port. I can't find any information on "Reichert's" normal camera adapters.


Regards, Ichty

BrianBurnes
Posts: 7
Joined: Sun May 31, 2020 6:47 am

Post by BrianBurnes »

Hi Ichty,

Thank you for the detailed reply! This is very helpful.

I'm not entirely sure yet where all the optical issues stem from. I cannot seem to get the same sharpness through the camera as through the eyepieces, so there may indeed be other problems with my system. I did notice that the blur is not uniform but has a preferential direction which gives me concern. The prism in the head seems clear, but I may have to disassemble the head to inspect the underside of the prism.

I believe I've been using EFSC (silent shooting mode I), but regardless my setup is not the most mechanically stable, so that may also be part of the problem.

I don't have a stage micrometer on hand, but that is a useful one to put on the list!
Optically the Canon 50/1.8 is known to work well; the coverage is not as wide as with a 40 mm so not many people use it; the plastic construction doesn't allow an adaptation that is as solid as with an old mechanical lens but it is usable. Also, the Canon 50/1.8 doesn't have a hard stop at infinity. You need to focus the lens at infinity, then switch off autofocus, maybe secure the setting with tape. The aperture should be fully open.
That is good to know! Mechanical stability may become a problem, as the distance from the trinocular head at which the eyepiece begins to focus is already quite high, likely to cause wobbling. I may need to build external support for the camera.

For future reference, if I wanted to eventually get a better suited mechanical lens for this purpose, is there any one in particular you would recommend?
In practice, you should try to get a high eyepoint eyepiece as close to the font lens of the camera objective as possible.
Excellent. It should be feasible to print an adapter to bring the eyepiece as close as possible. I will be on the lookout for high eyepoint eyepieces, though I'm not sure they were made for this model.
A different question is how you would mount the eyepiece to the trinocular port. I can't find any information on "Reichert's" normal camera adapters.
From what I've been able to gather, the intended use of the trinocular port is with the "Photostar" film camera system:
https://www.capovani.com/iinfo.cfm?itemno=2601

This system seems quite rare and is likely not useful in the digital era, and a homemade solution is required. I'm in the process of printing an eyepiece adapter to hold in my makeshift phototube, hopefully that will bring me closer to acceptable image quality.

Thank you again for your help!

Pau
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Post by Pau »

Posting pictures of your system, in particular of the camera port could be helpful to get advice

Some links to images or this kind of trinocular microscope I've found googling:

https://www.ebay.com/itm/360746746458 , an auction showing an actual camera adapter...not sure if original or not

https://www.dotmed.com/listing/microsco ... iv/2295550

https://caeonline.com/buy/microscopes/l ... iv/9000453

Someone who was a bit rude with his adaptation
https://www.photomacrography.net/forum/ ... 348#191348

And some ideas for afocal:
https://www.photomacrography.net/forum/ ... hp?t=15607
Pau

Ichthyophthirius
Posts: 1152
Joined: Thu Mar 07, 2013 5:24 am

Post by Ichthyophthirius »

BrianBurnes wrote: That is good to know! Mechanical stability may become a problem, as the distance from the trinocular head at which the eyepiece begins to focus is already quite high, likely to cause wobbling. I may need to build external support for the camera.

For future reference, if I wanted to eventually get a better suited mechanical lens for this purpose, is there any one in particular you would recommend?
I recommend from personal experience the
Pentax-M SMC 40/2.8 (mechanical)
but if you absolutely can't find a dust-free example you can use the
Canon EF 40/2.8 STM

Get around any issues with mechanical stability (for good) by mounting your camera to a copy stand like this http://www.krebsmicro.com/microsetup2/0045.jpg but with your camera lens attached. Thereby you mechanically un-couple your camera from the microscope.

BrianBurnes
Posts: 7
Joined: Sun May 31, 2020 6:47 am

Post by BrianBurnes »

Some updates on this: I redesigned the 3D printed trinocular adapter and that seemed to help a bit with the direct projection setup. I also designed a few bits for an afocal setup, but sadly the eyepiece holder was destroyed in the mail, and I ended up having to improvise by wedging an eyepiece into the adapter tube with some cardstock:

Image

I did a direct comparison between both a direct projection and an afocal setup. The mechanical setup goes something like 3D printed adapter -> M42 thread -> macro extension tubes -> helicoid -> M42-to-EF adapter for direct projection. For afocal, there sits an additional 10x eyepiece and a Canon 50mm f/1.8 lens between the camera and the helicoid.

Pictures of the two setups below: Direct projection (left), Afocal (right)
ImageImage

I did not have a microscope calibration slide, but I did have a glass reticule with a fine line grating intended for an eyepiece, which I put under the microscope for a comparison.

Below I'm showing results from both direct projection and the afocal setup, at 40x/100x/400x magnification both at horizontal and vertical orientation of the reticule. There is no cover glass, just the glass reticule sitting on top of a microscope slide (so not optimal). Images were shot by focusing through the eyepieces, then adjusting the helicoid until the camera was parfocal with the eyepieces. For the afocal setup, I adjusted the helicoid without the camera attached until the image looked sharp through the eyepiece in the adapter tube. I then attached the camera, focused at infinity.
Results below:

Direct projection: 40x, 100x, 400x (click images for full-res)
ImageImageImage
ImageImageImage

Afocal: 40x, 100x, 400x (click images for full-res)
ImageImageImage
ImageImageImage


While I don't know what the quality ceiling is for this scope/camera combination, I can't say I'm fully satisfied with either of these. The direct projection setup is acceptable, but especially at lower magnification, the image looks a bit hazy. There is also a lot of chromatic aberration towards the edges, which is not great. I suspect the visual field of the camera is larger than intended and the objective is pushed a bit too far at the edges of the image, so cropping the outer 25% or so may be necessary.

The afocal setup is really not very good. The images are hazy and the chromatic aberrations are extreme. Aberrations are not symmetrical so it's likely the eyepiece is tilted slightly in this ad hoc setup. I'm not sure if things would improve greatly with a proper eyepiece holder.

For now it seems the direct projection setup just about usable. Images shot under more realistic conditions look something like this (click for full res):
Image

Even though the image looks very sharp in the eyepieces, the image from the camera just feels blurry even when shooting at the shortest exposure time. The 7D that I'm using has a low-pass filter which may be contributing, but overall it feels like the quality I'm getting out is less than it could be.

I'm curious if anyone has any ideas on how I could further improve this. Maybe there's a glaring mistake I'm making?

Another wrinkle in this is that EOS Utility refuses to remotely shoot video without a lens attached, which makes the direct projection setup a lot less convenient to use. Does a workaround for this problem exist?

rjlittlefield
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Post by rjlittlefield »

BrianBurnes wrote:EOS Utility refuses to remotely shoot video without a lens attached ... Does a workaround for this problem exist?
I expect that using a Canon-to-M42 adapter that is equipped for "AF-confirm" will take care of that problem. Those adapters include a chip that mimics having a lens attached. They are commonly available for around $10 on eBay, slightly higher on Amazon.

--Rik

Scarodactyl
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Post by Scarodactyl »

Just a little tilt will screw things up way mpre than it feels like they should.
I am surprised the afocal srtup is so tall. When I have gone that route the pancake lens is almost on top of the eyepiece.

BrianBurnes
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Joined: Sun May 31, 2020 6:47 am

Post by BrianBurnes »

I expect that using a Canon-to-M42 adapter that is equipped for "AF-confirm" will take care of that problem.
Thanks for that tip! I will get one of those and see if that fixes the problem.
Just a little tilt will screw things up way mpre than it feels like they should.
I did try tilting the camera/adapter tube, but other than moving the image slightly it did not seem to make much of a difference. That's unfortunate as it would have been an easy fix, but at least the setup is not too fickle.
I am surprised the afocal srtup is so tall. When I have gone that route the pancake lens is almost on top of the eyepiece.
The eyepiece is nearly touching the lens, but it has to be quite far from the head for the image to be in focus. The length was surprising to me, but any shorter and the image is not in focus when looking through the eyepiece in the tube.

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

HyRe: Reichert Microstar IV afocal setup?

Post by Scarodactyl »

Something is definitely wrong if the eyepiece has to sit that high. Not sure what of course, but there must be more than just a tube lens inside. Not very helpful, I know, but it is very odd.

Ichthyophthirius
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Joined: Thu Mar 07, 2013 5:24 am

Re: HyRe: Reichert Microstar IV afocal setup?

Post by Ichthyophthirius »

Scarodactyl wrote:
Sun Jun 21, 2020 10:38 pm
Something is definitely wrong if the eyepiece has to sit that high. Not sure what of course, but there must be more than just a tube lens inside. Not very helpful, I know, but it is very odd.
Oddly, it was really designed that way! This seems to be the Reichert phototube: https://caeonline.com/buy/microscopes/l ... iv/9000453

Ichthyophthirius
Posts: 1152
Joined: Thu Mar 07, 2013 5:24 am

Re:

Post by Ichthyophthirius »

BrianBurnes wrote:
Sat Jun 20, 2020 10:59 am
I did not have a microscope calibration slide, but I did have a glass reticule with a fine line grating intended for an eyepiece, which I put under the microscope for a comparison.
Hi Brian,

The graticule glass is too thick for the 40x objective. You need to place the graticule upside down (markings on top of the glass), then cover with a 0.17 mm coverslip and thin layer of water in between.

Both adapations don't look too bad to me but the non-symmetrical colour fringing indicates that something is tilted, probably the eyepiece. There might always be some fringing as these are "just" planachromatic objectives, but at least it should be symmetrical.

Could you compare your afocal to some images you shoot afocally just through the binocular tube eyepiece with a tripod?

Regards, Ichty

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