Camera FOV area equals eyepiece FOV- Why?

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cwilli62
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Camera FOV area equals eyepiece FOV- Why?

#1 Post by cwilli62 » Thu Dec 29, 2022 1:06 am

I've done quite a bit of research at this point but simply cannot find the answer to my question. I know it's out there in someone's head that is more experienced than me.

I got some help from some community members when trying to find a camera. In the end, with the setup that I chose, with a 40x objective, the area of the rectangular field of view on my computer monitor is roughly equal to the circular area FOV through eyepieces that are 10x/18. I can't figure out why this is the case. There is no vignetting. How are the areas roughly equal? Does the specific trinocular port have something to do with it? If I was trying to help someone else do the same thing on a different microscope, is there an equation or procedure that I could follow to get there?

See this thread from my initial inquiry for an idea of what I'm talking about:
https://www.microbehunter.com/microscop ... 56#p124056

Microscope: LW i4 infinity microscope with plan objectives
Camera: Olympus E-M1 mark ii
Adapters: MFT to c-mount adapter AND C-mount camera adapter for Nikon ISO 38mm port

Dennis
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Re: Camera FOV area equals eyepiece FOV- Why?

#2 Post by Dennis » Thu Dec 29, 2022 1:27 am

cwilli62-

Is it as simple as-

https://www.microbehunter.com/microscop ... ng#p130404

or not ??

cwilli62
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Re: Camera FOV area equals eyepiece FOV- Why?

#3 Post by cwilli62 » Thu Dec 29, 2022 3:02 am

Thanks for the reply. However, I'm not wondering about the size of the FOV in terms of measurement. I'm wondering how the area of FOV on a rectangular screen can be roughly equal to that of a circular view when looking through the eyepieces.

I was under the impression from my research that a camera sensor would either show the whole circular FOV but with vignetting or that it would not have vignetting but would cut off some portion of the area of the circle.

Obviously, with a rectangle and a circle compared with one another, I'm not seeing the exact same portion of the slide on the camera that I do through the eyepieces. But it's a mystery to me how the total areas are so close in number.

Dennis
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Re: Camera FOV area equals eyepiece FOV- Why?

#4 Post by Dennis » Thu Dec 29, 2022 3:33 am

The camera is in a hole at a different distance than the other eyepiece hole
OR... the camera is focused out a step a little before rectangling (cropping)

See I might have to adjust my eye pieces but not really cause one eye would be stronger than the other is why you would but there is a camera in a eye piece hole or tri head hole and what I see in my one eyepiece if focused needs refocus with me just looking at my PC monitor.

Don't know if I am helping or what but ....

Dennis
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Re: Camera FOV area equals eyepiece FOV- Why?

#5 Post by Dennis » Thu Dec 29, 2022 3:42 am

See maybe-
You are thinking everything should all be calibrated to all work perfect, everything just align and be so correct.

"Only in the movies."

Just kidding around !

BramHuntingNematodes
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Re: Camera FOV area equals eyepiece FOV- Why?

#6 Post by BramHuntingNematodes » Thu Dec 29, 2022 5:08 am

Not sure I understand the question yet. What would you expect the fovs to be? It might require a little bit of knowledge of the ray path, how the eyepiece picks up the image, and the camera sensor size.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

Scarodactyl
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Re: Camera FOV area equals eyepiece FOV- Why?

#7 Post by Scarodactyl » Thu Dec 29, 2022 3:23 pm

Area is an odd way to measure this, but it's about what you'd expect. A 10x/18mm eyepiece has an area of pi x 9^2 (254 mm^2) while the mft sensor has an area of 17.3 x 13 (224mm^2)
You might be confused because your camera's field of view goes outside the area covered by the eyepieces. The reason is simply that the microscope's objectives can deliver an image big enough for aps-c (with some loss in quality outside the central zone) and the cheap 10x/18 eyepieces are bottlenecking it. That said I hsppen to have one of this model and mine came with 10x/20 eyepieces, but can easily cover 10x/22s which has the same diagonal as your camera sensor.

cwilli62
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Re: Camera FOV area equals eyepiece FOV- Why?

#8 Post by cwilli62 » Fri Dec 30, 2022 1:43 am

BramHuntingNematodes wrote:
Thu Dec 29, 2022 5:08 am
Not sure I understand the question yet. What would you expect the fovs to be? It might require a little bit of knowledge of the ray path, how the eyepiece picks up the image, and the camera sensor size.
My thought/understanding is that the FOV through camera would be smaller than that of eyepieces with no vignetting. OR same size as FOV through eyepieces but with some vignetting.
Scarodactyl wrote:
Thu Dec 29, 2022 3:23 pm
Area is an odd way to measure this, but it's about what you'd expect. A 10x/18mm eyepiece has an area of pi x 9^2 (254 mm^2) while the mft sensor has an area of 17.3 x 13 (224mm^2)
You might be confused because your camera's field of view goes outside the area covered by the eyepieces. The reason is simply that the microscope's objectives can deliver an image big enough for aps-c (with some loss in quality outside the central zone) and the cheap 10x/18 eyepieces are bottlenecking it. That said I hsppen to have one of this model and mine came with 10x/20 eyepieces, but can easily cover 10x/22s which has the same diagonal as your camera sensor.
I think this gets to the main point of confusion for me. I didn't realize that the eyepiece cuts off part of the viewing area that objective lens is capable of. That makes a lot of sense!

So...this may be a simple question...but how do I figure out the maximum possible viewable area with only an objective lens of any given magnification (with no eyepiece being used, obviously)?

Dennis
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Re: Camera FOV area equals eyepiece FOV- Why?

#9 Post by Dennis » Fri Dec 30, 2022 2:40 am

See I sound like I am starting trouble but my thought is-
What is the point of finding out the maximum view?

Usually 99 percent of the time you do not need that outer borderline space.
And if you would then you switch to a lower objective to pan out a notch or more.

Scarodactyl
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Re: Camera FOV area equals eyepiece FOV- Why?

#10 Post by Scarodactyl » Fri Dec 30, 2022 2:54 am

cwilli62 wrote:
Fri Dec 30, 2022 1:43 am
So...this may be a simple question...but how do I figure out the maximum possible viewable area with only an objective lens of any given magnification (with no eyepiece being used, obviously)?
Not a simple question really. You can test it to some extent with wider field eyepieces, but this model has 23mm eyepiece tubes so about 22mm is the widest you can test to. To test mine I removed the head and replaced it with an Olympus u-tlu eith an aps-c camera directly mounted, which produced an image out to the edge of the sensor (with some loss of quality but not nearly as much as you might expect). You can see my testing here https://www.microbehunter.com/microscop ... 24&t=15386
It will likely produce some kind of image much further out than that, depending on the tube lens used. Some microscope heads will crop the image significantly. Image quality will also continue to drop as you go further out, but that said Macro_Cosmos posted results from putting his Olympus CX23's 40x objective onto full frame with just a bit of cropping and they were impressive, though I don't know the exact setup https://www.photomacrography.net/forum/ ... p?p=284474
This info is only really relevant if you want to direct project onto a larger sensor or upgrade to wider-field eyepieces, but these are nice options to have. I certainly plan to eventually do that with my own lmscope eventually. When you're on the razor's edge of diffraction it can be nice to tip the equation in your favor for photography if gear permits, and wider fov eyepieces are a nice luxury if you're into them.

cwilli62
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Re: Camera FOV area equals eyepiece FOV- Why?

#11 Post by cwilli62 » Fri Dec 30, 2022 4:48 am

Dennis wrote:
Fri Dec 30, 2022 2:40 am
See I sound like I am starting trouble but my thought is-
What is the point of finding out the maximum view?

Usually 99 percent of the time you do not need that outer borderline space.
And if you would then you switch to a lower objective to pan out a notch or more.
Until recently, for the past 5 years, I have been observing and counting microbiology through the eyepieces. Every once in a while I would have to use a camera and my old setup would only show approximately 1/4 of the FOV that I saw through the eyepieces. Then I decided that I wanted to try to do microbiology assessments on a computer screen so I started to do research on getting a new camera setup. I thought, as explained above, that it was not practical to get a similar FOV on a computer monitor through a camera that I do through the eyepieces. I was pleasantly surprised that it is possible. This matters because I wanted to be able to view the same number of FOV on the monitor and get a similar total area of the cover slip viewed....so that when I compute the number of organisms viewed, the standard deviation would be similar between the two methods. Otherwise, as with my old setup, I would have to view 4 times the field of views on the camera as I did with the eyepieces to view the same total area and not throw off my SD to an unacceptable number.

I would like to figure out the maximum because it would be nice to help some of my colleagues who have asked, for their particular microscope, how to do something similar. Or to know in case I wanted at some point in the future to get a larger FOV on the computer screen to be able to see more of the material under the cover slip at one time. And because I want to learn the intricacies of my system. Figure out the full capabilities and parameters...maybe just to know...and because perhaps it will be useful someday.

cwilli62
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Re: Camera FOV area equals eyepiece FOV- Why?

#12 Post by cwilli62 » Fri Dec 30, 2022 4:57 am

Scarodactyl wrote:
Fri Dec 30, 2022 2:54 am
cwilli62 wrote:
Fri Dec 30, 2022 1:43 am
So...this may be a simple question...but how do I figure out the maximum possible viewable area with only an objective lens of any given magnification (with no eyepiece being used, obviously)?
Not a simple question really. You can test it to some extent with wider field eyepieces, but this model has 23mm eyepiece tubes so about 22mm is the widest you can test to. To test mine I removed the head and replaced it with an Olympus u-tlu eith an aps-c camera directly mounted, which produced an image out to the edge of the sensor (with some loss of quality but not nearly as much as you might expect). You can see my testing here https://www.microbehunter.com/microscop ... 24&t=15386
It will likely produce some kind of image much further out than that, depending on the tube lens used. Some microscope heads will crop the image significantly. Image quality will also continue to drop as you go further out, but that said Macro_Cosmos posted results from putting his Olympus CX23's 40x objective onto full frame with just a bit of cropping and they were impressive, though I don't know the exact setup https://www.photomacrography.net/forum/ ... p?p=284474
This info is only really relevant if you want to direct project onto a larger sensor or upgrade to wider-field eyepieces, but these are nice options to have. I certainly plan to eventually do that with my own lmscope eventually. When you're on the razor's edge of diffraction it can be nice to tip the equation in your favor for photography if gear permits, and wider fov eyepieces are a nice luxury if you're into them.
Hmm...I think that this answers the question that I asked but not the one that I THOUGHT that I was asking. Haha. That is pretty cool that the testing can be done by taking the head off...and then even just projecting the image from there.

Assuming that I want to keep the head on the microscope so that I can peak in the eyepieces sometimes, is there a simple way to know/measure/calculate the maximum size of the image that can viewed through the trinocular port? At that point, because of the likely reduction in image size from the head of the microscope, is there a practical way to figure this out?

Scarodactyl
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Re: Camera FOV area equals eyepiece FOV- Why?

#13 Post by Scarodactyl » Fri Dec 30, 2022 5:24 am

Oh, one way is to just hand hold your camera over the trinocular port and move it around to scan through the available image. That will give you an idea of where the edges are.
Btw I just checkes again and contrary to what I had initially thought the LW i4 is not built on the same frame as the polarizing model I have. So who knows how similarly it may behave--probably pretty close but nk guarantees.

cwilli62
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Re: Camera FOV area equals eyepiece FOV- Why?

#14 Post by cwilli62 » Fri Dec 30, 2022 2:14 pm

Cool. Yeah, that's worth a shot to try.

Now you got my head buzzing thinking about taking the scope head off and projecting a huge image. :D Something to play around with in the future.

Scarodactyl
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Re: Camera FOV area equals eyepiece FOV- Why?

#15 Post by Scarodactyl » Fri Dec 30, 2022 4:37 pm

Just to be clear if you take the head off you can't use it bare, you do need a lens to focus the image onto your camera. The one in the microscope head has a focal length of 180mm, using a longer fl will magnify the image further and a shorter fl will shrink it down. Some systems need very specific characteristics in that lens to get good results but on this one you should be fine with any decent lens of about the right focal length.

cwilli62
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Re: Camera FOV area equals eyepiece FOV- Why?

#16 Post by cwilli62 » Mon Jan 02, 2023 10:45 pm

Gotcha. I'll keep that in mind.

GerryR
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Re: Camera FOV area equals eyepiece FOV- Why?

#17 Post by GerryR » Tue Jan 03, 2023 12:17 am


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