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Optical system for video
Posted: Wed Aug 31, 2022 6:37 am
by shauttra
Hi there microbe hunters!!
I am filming a microscopic world for a while, and now i want some upgrade. At the moment i have microscope objectives with standard 160mm tube. Now i am using camera in prime focus. As i understand, this is not the best way to do things. So i decided to switch to projection photo eyepiece. But here i dont understand few things. Which type of objectives works with projection eyepiece - 160mm or infinity-corrected, or both?
Thanks!!
Janis.
Re: Optical system for video
Posted: Wed Aug 31, 2022 1:14 pm
by BramHuntingNematodes
Well, there have been many projection eyepieces made. Which one is yours?
Re: Optical system for video
Posted: Wed Aug 31, 2022 3:31 pm
by blekenbleu
shauttra wrote: ↑Wed Aug 31, 2022 6:37 am
Now i am using camera in prime focus. As i understand, this is not the best way to do things.
That is a generality. Some modern microscopes offer prime focus video camera options.
If still image quality is acceptable, then video quality should also be acceptable.
For some microscopes (e.g. Nikon CF), prime focus (AKA direct projection) at least equals that with a photo relay lens.
Some infinity objectives are fully corrected by their microscopes' tube lens,
then that tube lens can be used for prime focus / direct projection.
Infinity objectives that do not depend on tube lens for additional correction
can be focused near infinity by a camera telephoto lens.
A zoom telephoto lens can simplify optimizing video field.
For those microscopes that depend on matching oculars for correction,
afocal can yield better results than possible with a photo relay lens
which does not exactly correct your objectives and have correct magnification for your camera sensor;
sourcing such a relay lens may be problematic, expensive or impossible.
Some microscope camera configurations are compromised
by a camera sensor not parfocal with eyepieces.
Correcting that, e.g. by a helicoid between camera and microscope,
will be wanted for either prime focus or with a photo relay.
Re: Optical system for video
Posted: Wed Aug 31, 2022 4:30 pm
by shauttra
BramHuntingNematodes wrote: ↑Wed Aug 31, 2022 1:14 pm
Well, there have been many projection eyepieces made. Which one is yours?
I have Nikon CF projection eyepiece. Today received
Made some experiments and not sure about results. Objectives are far from the best, but for visual observations they are really good. But i should search for something better anyway...
Re: Optical system for video
Posted: Wed Aug 31, 2022 4:38 pm
by shauttra
blekenbleu wrote: ↑Wed Aug 31, 2022 3:31 pm
shauttra wrote: ↑Wed Aug 31, 2022 6:37 am
Now i am using camera in prime focus. As i understand, this is not the best way to do things.
That is a generality. Some modern microscopes offer prime focus video camera options.
If still image quality is acceptable, then video quality should also be acceptable.
For some microscopes (e.g. Nikon CF), prime focus (AKA direct projection) at least equals that with a photo relay lens.
Some infinity objectives are fully corrected by their microscopes' tube lens,
then that tube lens can be used for prime focus / direct projection.
Infinity objectives that do not depend on tube lens for additional correction
can be focused near infinity by a camera telephoto lens.
A zoom telephoto lens can simplify optimizing video field.
For those microscopes that depend on matching oculars for correction,
afocal can yield better results than possible with a photo relay lens
which does not exactly correct your objectives and have correct magnification for your camera sensor;
sourcing such a relay lens may be problematic, expensive or impossible.
Some microscope camera configurations are compromised
by a camera sensor not parfocal with eyepieces.
Correcting that, e.g. by a helicoid between camera and microscope,
will be wanted for either prime focus or with a photo relay.
Oh, thanks!
So, if i will try to use infinity lens with projection eyepiece (without correction tube lens) i will not get an image? Huh, sounds complicated
As i mentioned above, i just receive Nikon projection eyepiece. First impressions with china Plan lenses are not good... Simple prime focus image looks much better.
Re: Optical system for video
Posted: Wed Aug 31, 2022 5:33 pm
by blekenbleu
shauttra wrote: ↑Wed Aug 31, 2022 4:38 pm
So, if i will try to use infinity lens with projection eyepiece (without correction tube lens) i will not get an image?
As i mentioned above, i just receive Nikon projection eyepiece. First impressions with china Plan lenses are not good... Simple prime focus image looks much better.
Projection eyepiece and infinity lens are mutually exclusive.
If an infinity objective is focused
directly on a camera sensor,
it is being used out of specification. If the camera is attached to a trinocular head photo port,
then there should be a tube lens converting objective parallel rays back to finite.
Nikon CF 2.5 PL optics expect about 100mm separation between its top and the camera sensor
to be parfocal with eyepieces, supposing that photo lens is correctly focused at the primary image plane.
In my experience, CF PL optics reduce contrast.
FWIW "microscope objectives with standard 160mm tube" are NOT infinity,
but may or may not be internally corrected.
Snapshots of your setups could be helpful.
Re: Optical system for video
Posted: Wed Aug 31, 2022 6:25 pm
by shauttra
Here is my man cave setup.
Still playing around. At the moment best quality is with camera zoom lens attached to camera. Projection eyepiece looks like an amplifier of all objective distortions. Probably not a best combination with no brand objective.
But anyway - visual observation image quality is great, crispy and sharp, without any chromatic aberrations.
Re: Optical system for video
Posted: Wed Aug 31, 2022 10:36 pm
by blekenbleu
shauttra wrote: ↑Wed Aug 31, 2022 6:25 pm
Here is my man cave setup.
At the moment best quality is with camera zoom lens attached to camera.
OK, now there are two posts with the same images.
Re: Optical system for video
Posted: Thu Sep 01, 2022 5:30 am
by shauttra
Re: Optical system for video
Posted: Thu Sep 01, 2022 8:31 pm
by blekenbleu
FWIW, that vertical tube seems longer than 160mm..
I estimate about 200mm from microscope arm to camera lens flange,
supposing extension tube o.d. is approx 46mm.
Ideally, one would focus an object using the regular microscope head and eyepiece,
then replace that head with extension tubes and camera
without adjusting stage focus.
This typically requires a helicoid among the extension tubes
to get camera sensor parfocal with regular eyepieces
and objective focused as designed.
Your zoom lens setup seemingly is not being shown..?
Another image just shows a lens (Nikon CF projection?) clamped in an adapter to a camera,
which is appears to be the same setup shown sticking out of a binocular microscope eye tube
in the third image. Is the object focused in the other eye tube ocular?
My guess is that distance from lens to camera sensor is less than ideal for the CF projection.
Re: Optical system for video
Posted: Fri Sep 02, 2022 7:03 am
by shauttra
First image is camera on binocular head (not safe). But here i can get 160mm distance for projection eyepiece. Only distance from eyepiece to camera is less than 100mm.
In third picture binocular head is removed, but here with extension rings i get exactly 160mm from objective rim to eyepiece shoulder, and from eyepiece to camera 100mm. I can move eyepiece in tube and fix it with screw. Camera is BlackMagic cinema with crop factor 2x. So the image circle is larger because projection eyepiece is for full frame camera.
Image quality with proper distances are better now. I guess i have reached maximum image quality for these objectives. Should try something better.