Microscope adapter for Canon Eos 5D

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Gurkan
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Post by Gurkan »

If I understand your earlier message it sounds like you had the adjustable tube (upper tube) as low (short) as possible, but it was necessary to remove the T-mount and position the camera even closer to get it in focus. Is this correct? If so, then it sounds like the eyepiece is positioned slightly too high. (However... if this is the case, and the eyepiece is positioned as low as the adapter allows, then you have a problem).
Yes, upper tube is as low as it can get (eyepiece that sits in the lower tube as close to the camera as possible), it can only move uppwards, moving the camera away from the eyepiece.
But when I raise the eyepiece( i.e. moving it closer to the camera) aprox 5mm, I can actually get a sharp image on the camera sensor, that's why I thought a thinner T2 adapter would produce the same result (camera sensor closer to the eyepiece) as raising the eyepiece. If that is a wrong assumption, then I really don't understand how this afocal projection works I'm afraid.

Am I totally off track now? :?

Gurkan
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Post by Gurkan »

(If viewing with 10X eyepieces most people typically like about a 2.5X magnification into a full-frame body and about a 1.6X magnification into an APS body).
I have a 5D MK3 and the photo eyepiece is a 10X and that pretty much has the same magnification and crop as looking through the regular viewing eyepieces.
Wouldn't a 2.5X yield a much smaller scale and visual representation?

/Gurkan

Charles Krebs
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Post by Charles Krebs »

If that is a wrong assumption, then I really don't understand how this afocal projection works I'm afraid.
.

Generally best to think in terms of two different methods... one is projection and the other afocal:

Projection into a lens-less camera body:

1) This can be "direct projection" from the objective onto the sensor. (Not very common with most compound microscopes. With many it is not even possible).

2) Projection via a dedicated, designed projection photo-eyepiece. These are different from "viewing" eyepieces. They were made specifically to mount in a trinocular tube to project the objectives intermediate ("real") image onto film or a sensor. They typically were made with lower magnifications such as 1.67X, 2X, 2.5X, 3.3X, 4X. The power (magnification) selected for use depended largely on the camera format (film or sensor size).

3) Projection using a "normal" viewing eyepiece. A viewing eyepiece produces "virtual image" that requires the lens of the eye (or a camera lens if using a camera) to form a real image on the retina (or sensor). But.... by raising the "viewing" eyepieces some amount from the position it normally occupies you effectively "change" it into a projective eyepiece. The more it is raised from it's "base" position the smaller the projected "real" image (and the closer to the eyepiece that projected image occurs). This is what we are trying to accomplish with your adapter.

The afocal method is different from the "projection "method. With the afocal method, the camera tube is set up with an eyepiece that produces an image viewable by eye, (This type of image is referred to as a "virtual image"... it requires another lens to be seen or recorded). Ideally it will be in focus (to the eye) at the same microscope focus setting where the viewing eyepieces are in focus. The camera now has a lens attached (usually focused at "infinity"). The camera lens takes the place of lens in your eye. The camera with lens are positioned to "look" through the eyepiece. It then produces a "real" image onto the sensor.

It would really be helpful know if there is any way to have the eyepiece you are using placed in the adapter you have so that it is in focus (by eye) simultaneously with the viewing eyepieces. I am trying to determine if the adapter you have elevates the eyepiece too much even at the "lowest" location of the eyepiece.
I have a 5D MK3 and the photo eyepiece is a 10X and that pretty much has the same magnification and crop as looking through the regular viewing eyepieces.
Wouldn't a 2.5X yield a much smaller scale and visual representation?
No. As soon as you "elevate" the eyepiece above it's "base" location (the location where it is in focus -by eye- simultaneously with the viewing eyepieces), the 10X magnification no longer applies. The actual magnification into the camera now depends on how much it has been elevated. With a full frame camera (24x36mm sensor) a 2.5X projection of the intermediate image will provide nearly the exact field you see when using typical 10X viewing eyepieces.

The "intermediate" real image formed by the microscope objective is typically a circle about 20mm in diameter. Your 10X eyepieces see an 18mm diameter circular section of that intermediate image. (That's what the FN 18 marked on the eyepiece refers to). The diagonal of your camera sensor is 43mm. If you magnify that 18mm intermediate image 2.5X into the camera you have enlarged it to a 45mm diameter circle at the camera sensor. An excellent "fit" for a sensor with a 43mm diagonal. If you were to actually magnify that 18mm intermediate image 10X at the camera sensor it would be a circle of 180mm diameter. The sensor is only 43mm diagonally so it would "see" and record less than 1/4 of the image you are seeing through the viewing eyepieces... your pictures would look like a severe crop of the view you are looking at. In the camera you would be "wasting" more than 75% of the image produced by the objective.

If you have not seen this PDF you might find it helpful:
http://www.krebsmicro.com/pdf/trinoc_a3.pdf

Pau
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Post by Pau »

The Charles response can't be more clear (thanks to avoid me the futile effort to try it :D )

About afocal, there are many good references at the forum and outside it, let me link my own:
http://www.photomacrography.net/forum/v ... 9265#99265
Pau

Gurkan
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Joined: Tue Dec 02, 2014 3:13 pm

Post by Gurkan »

Charles. Thank's for the detailed explanation of how this works, I really appreciate the time you put in to it!!!

I'm reading it over and over again to try to really grasp the different concepts.
Find it pretty hard but eventually I will understand it. :D

I will try tonight to investigate the distance of my eyepiece I have.
I've been living under the assumption that is was a dedicated "photo eyepiece" I had purchased, that made things a bit confusing.

The pdf will surely clear things up for me :) Thank's for that!


@pau:
Your input has been well appreciated, don't think otherwise :)

/Gurkan

Gurkan
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Post by Gurkan »

Ok, so I will post these examinations in consecutive posts since my three kids demands my attention most of the time. :D

#1: trying to have the photo eyepice parfocal with the viewing eyepieces:
When the focus is set viewing through the scope, the focal plane (looking through the photo eyepiece in the tube) sits "above" the specimen, i.e. I need to move the focus stage closer.
Lifting the photo eyepiece from the base position makes it more unfocused.
This concludes the photo eyepiece actuallly needs to be placed further down to achieve the parfocal, right?

Unfortunately there is no way to place it further down the tube.

Are these observations correct assumptions?

/Gurkan

NationalMicroscope
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Post by NationalMicroscope »

LM Microscope Adapter: Canon EOS 5D Mark II with a full-frame sensor is Good for you. :o

Gurkan
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Joined: Tue Dec 02, 2014 3:13 pm

Post by Gurkan »

NationalMicroscope wrote:LM Microscope Adapter: Canon EOS 5D Mark II with a full-frame sensor is Good for you. :o
Thank's for the tip!
Is that the "best" solution for my setup?

/Gurkan

Edit:
Actually, that one won't work since my trinocular port is only 21mm in diameter.

Gurkan
Posts: 25
Joined: Tue Dec 02, 2014 3:13 pm

Post by Gurkan »

#2: lifting the photo eyepiece aprox 5 mm.

So.
The only way to get my camera setup to work is to raise the eyepiece.
Unfortunately I can't seem to get it parfocal with the viewing eyepieces.

This is the field of view straight from the camera:

Image

This is just a testshot with a piece of hair using darkfield. Some sharpening and defringing in LightRoom, no manual crop, for some reason it has been autocropped by LR :

Image

Same frame, 100% crop:

Image

/Gurkan

Charles Krebs
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Post by Charles Krebs »

Gurkan,

From everything you have said so far it sounds like the adapter (as least how you are using it) does not allow sufficient adjustment capability to set it up so that it is parfocal with the viewing eyepieces. It sounds like you need the ability to position the eyepiece "lower" and/or the ability to get the camera lower. If this is an adapter offered by the microscope manufacturer then you should question them.

You can likely still take pictures by focusing the camera using live view. However this means the "viewing eyepiece" focus will be different from the camera. This is not only inconvenient, but is really not good technique. Unless the difference in focus (between camera and viewing eyepieces) is small, you will be introducing spherical aberration that has the potential to degrade image quality. In reality, as long as there is not a large focus discrepancy, image degradation will not be that great (or perhaps even noticeable) with a modest NA objective (like a 4X, 10X or even 20X). But this effect will increase as the NA of the objective used increases.

(Objectives are designed to very specific parameters. One is the lens to subject distance. If the microscope is properly set up, then when the view through the eyepieces is in focus these parameters are met. If you need to alter the focus in order to get a camera in focus then you are deviating from the "ideal" to some degree. Any negative effects from doing this increase as the NA of the objective goes up).

Gurkan
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Joined: Tue Dec 02, 2014 3:13 pm

Post by Gurkan »

Thank's Charles!

It's exactly as you describe it!
The eyepiece needs to be lower or the camera needs to be closer.
Something is not working correctly.
Using live view is of course a way to handle it but Canon Utilitys Live view don't offer the same visual accuracy an have a big latency built in it using USB connection unfortunately...
Just as you write, not a very good workflow in the long run when it comes to focus stacking.
I really want/need the best possible optical solution I can get my hands on for my scope.

Any advise if the seller can't handle this problem? What would be the best possible solution in my case?

/Guran

Gurkan
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Post by Gurkan »

BTW, the field of view shown above, is that a "normal" fov or should it be more cropped? Seems like wasting a lot of pixel resolution.

/Gurkan

Charles Krebs
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Post by Charles Krebs »

BTW, the field of view shown above, is that a "normal" fov or should it be more cropped? Seems like wasting a lot of pixel resolution.
No, not really "normal". If you had more adjustment capability you would likely prefer a framing in the camera something like this:

Image

If you had the adjustment capability you would be able to go through a complete range from a full circular image (with black surround) to a very tight crop of the image seen through the eyepieces. Whatever you wanted. (And any magnification you chose could be completely parfocal with the eyepieces.

This is what I was referring to earlier when I said:
To use an eyepiece as a projective lens it is a bit of a "delicate dance" between eyepiece elevation and camera height. When the eyepiece height changes even a little, the camera height needs to be adjusted. The higher the eyepiece is elevated from the "base" viewing position, the lower the magnification into the camera body, and the closer the camera body must be to the eyepiece. Conversely, the less the eyepiece is elevated the higher the magnification and the farther away the camera must be positioned. It is very possible to position the eyepiece so that needed camera adjustment exceeds the what is possible in the adapter.
See what the manufacturer has to say. Since that adapter has a T-mount it would seem like it was intended to be used with SLR cameras. The Canon body adds 44mm to the overall "extension" but it is not excessive in this regard (Nikon and M42 are actually a little deeper). "C" mount cameras have a much smaller body depth, but adapters for them typically come with the "C" mount built in, not a T-mount. Again this would have me thinking that it was intended for SLR cameras.

One thing that concerns me a little is that you said the photoport has a 21mm diameter. (Below is picture you posted):
Image

This 21mm diameter is not any "standard" I am aware of, so you might need to rely on the manufacturer (or DIY) for a solution. But first see what Labomed has to say.

BTW... if possible, post a picture of the adapter and eyepiece in place in the camera port (but with the outer large tubes removed). It might be helpful to see how the eyepiece sits inside the adapter.

Gurkan
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Joined: Tue Dec 02, 2014 3:13 pm

Post by Gurkan »

If you had the adjustment capability you would be able to go through a complete range from a full circular image (with black surround) to a very tight crop of the image seen through the eyepieces. Whatever you wanted. (And any magnification you chose could be completely parfocal with the eyepieces.
This is exactly how I expected it to be when I ordered the setup, unfortunately this is not the case.
To bad the seller recommended this particular microscope, even though I clearly explained my needs and I payed quite a bit for it.

In retrospect I would have done my research MUCH better...

I will post a picture of the eyepiece sitting in the lower tube.

Thank's Charles!

/Gurkan

Gurkan
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Joined: Tue Dec 02, 2014 3:13 pm

Post by Gurkan »

So.
This is the eyepiece sitting in the lower tube in it's original position.

Regarding the crop factor; I can of course raise the upper tube to get a tighter crop but that makes it more unfocused.

Image
Image

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