Eyepiece Camera Limits Visual Field from Eyepieces

[DonSchaeffer]

I was curious so I did some comparisons using a stage micrometer. The eyepiece camera is 1.7 times smaller than the 25 x eyepiece and 4.7 times smaller than the 10x eyepiece. This has the illusionary effect of higher magnification but that depends on screen size.

[MichaelG.]

Bewildered by your numbers, until I realised ...

1.7 ÷ 25 = 0.068
4.7 ÷ 10 = 0.47
seems unlikely

4.7 ÷ 25 = 0.188
1.7 ÷ 10 = 0.17
seems logical

MichaelG.

[DonSchaeffer]

I am a crappy scientist. I lost my ability to calculate.

[DonSchaeffer]

I checked everything.
At the high power,
the 10x eyepiece covers a field of about .35 mm.
The 25x eyepiece covers a field of about .17 mm
The camera covers a field of .085 mm
So the camera is only 25% of the 10X eyepiece field
and the camera is only about 50% of the 25x eyepiece field.

[MichaelG.]

I checked everything.
At the high power,
the 10x eyepiece covers a field of about .35 mm.
The 25x eyepiece covers a field of about .17 mm
The camera covers a field of .085 mm
So the camera is only 25% of the 10X eyepiece field
and the camera is only about 50% of the 25x eyepiece field.

O.K. ... I understand what you are doing, and it all seems reasonable
The 25x eyepiece appears to have a narrower visual field than the 10x eyepiece
and the camera has a smaller field of view than either of them.

This is not surprising, but I don’t know what equipment you are using, so I can’t really comment any further.

... what were you expecting to see ?
... Happy to help if I can.

MichaelG.

[DonSchaeffer]

It just changed my view of things. I thought of the camera as a reproducing instrument roughly mimicking an eyepiece. I shouldn't have been surprised but now I think of the camera as a higher power eyepiece. It's like a 40x eyepiece.

[Scarodactyl]

Your camera has a small sensor, significantly smaller than the image circle produced by the objectives (or the objective+tube lens in an infinity system). If you look at your 10x eyepieces they will likely have a field number on them, 10x/18, 10x/20 etc. That field number is basically how large of an image circle the eyepiece is picking up to enlarge and send up to your eyeballs (the lens in your eye then reduces the image back down and focuses it nicely onto your retina). Even at the low end that's a diagonal of 18mm, and often the objective is actually producing an even bigger field of view which the eyepieces crop the center from. Based on rough calculations your camera probably has a 1/2.5" sensor, which is 5.76mm wide. So you can see why reducing optics would come in handy here--they can grab a section of that bigger image and concentrate it down so your camera will get to full FoV (and as a consequence a much brighter image as well). This might also explain some of the other issues you've had on your camera--low light levels could make it struggle.
0.5x c mount eyepiece adapters are pretty commonly available in varying degrees of quality. Your camera could take more reduction than that but I am not sure what availability is like for greater reductions.

[DonSchaeffer]

Thanks very much Scarodactyl. I like to use the camera for viewing. I've all but given up on using the eyepieces. I try to portray what I see and see as much as I can. I make up technique as I go along. To me its more of an art than a science. Take a look at some of my recent views of cells and of microbes. I'm using things that I learned here, but fitting them to my own circumstances. I want to build an retinal device for continuously adjusting aperture of the substage light so I bought one. I want a workable filter holder. And I'm working on a way of getting top stage light more precisely to my subject using light conducting plastic cable. This forum is really fun and enlightening.