Stereo microscope photo port projection lens not parfocal with eyepieces

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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einman
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Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#31 Post by einman » Tue Dec 07, 2021 1:12 am

Nikon SMZ-U has a resolution of 270 lp/mm with the 1x E plan 420 LP with the 1.5X objective and 540 lp with the 2x objective. These numbers are at max 7.5x

NA respectively 0.1, 0.14 and 0.18. The newer stereoscopes have more than double that resolution with the Leica SM205C for example having a resolution of 0.35 and 1050 lp/mm at max magnification. Not too shabby.

Interestingly enough the B&L stereozoom7 had an na of 0.1 and 300lp/mm ..not too far off from the SMZ-U despite the age difference. Just an FYI

ClassMSpecie
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Joined: Sat Nov 06, 2021 3:25 am

Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#32 Post by ClassMSpecie » Thu Dec 23, 2021 3:33 am

Sorry for the very late reply. I have resolved the camera to eyepiece parfocal issue--one of the photo tube adapter got stuck and was not all the way in. I have another issue with DSLR exposure times. With a 50W desk lamp shining directly on a specimen, it typically takes 1-2 second exposures (800 ISO) to get noise-free images. Videos are very noisy at best at this setting. Is this normal? Would upgrading to a 2.5x relay lens from a 5x relay lens help reduce exposure times significantly? Any input would be very helpful.

Thank you in advance.

ClassMSpecie

Scarodactyl
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Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#33 Post by Scarodactyl » Thu Dec 23, 2021 4:00 am

5x is too strong for sure. Your lighting is probably too weak for higher mags. I would also suggest locking iso at its lowest setting and adding light to compensate for beat noise performance.

ClassMSpecie
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Joined: Sat Nov 06, 2021 3:25 am

Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#34 Post by ClassMSpecie » Thu Dec 23, 2021 4:44 pm

Thank you, I failed to mention that I was taking images at its max 75x magnification. Through the 10x eyepieces, projected images are plenty bright, so I automatically thought that the camera port would also send similarly bright light to the camera sensor. But in all fairness, I don't know how much light is lost or scattered due to additional mirrors, prisms, and lenses (including the 5x) through the photo optical path. I wished that I wouldn't have to use a 150W bulb fiber light as halogen bulbs are illegal/difficult to buy in California nowadays (energy demon). I looked into getting a LED fiber light, but boy they are costly. Can you recommend me a bright enough light that I can get affordably?

Thank you for your help in advance.

ClassMSpecie

Scarodactyl
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Joined: Sat Mar 03, 2018 9:09 pm

Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#35 Post by Scarodactyl » Thu Dec 23, 2021 5:22 pm

Your eyes have much better dynamic range than your camera, and subsequently stretching the light out a lot thinner doesn't help.
Simple gooseneck led lights have been a popular option for many photographers, though the once-favorite ikea model isn't sold anymore.

ClassMSpecie
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Joined: Sat Nov 06, 2021 3:25 am

Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#36 Post by ClassMSpecie » Thu Dec 23, 2021 6:15 pm

Thank you JPL on your analysis. I've found an old thread that discusses about relay lenses.

viewtopic.php?t=7628&start=60

From what I've gathered is that the 2.5x relay lens is really intended for full frame cameras. To cover an APS-C sensor with the 2.5x relay lens, I think you may need shorter extension tubes.

According to patta, he has 78mm spacers for APS-C and 128mm spacers for full frame cameras. To me, this indicates that the relay lens projects diverging light, so you can adjust your FOV based on spacing.

However, I do believe that direct projection is the way to go for APS-C based cameras, since less is always better in the optical path to me ($$$ and aberrations).

ClassMSpecie
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Joined: Sat Nov 06, 2021 3:25 am

Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#37 Post by ClassMSpecie » Thu Dec 23, 2021 6:18 pm

hm...I'll try to look for those IKEA ones. Thank you.

wabutter
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Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#38 Post by wabutter » Tue Dec 28, 2021 7:54 pm

Regardless of the microscope model, one factor that should be considered in low mag photomicrography is the parallax that can occur to the conjugate image plane

Does the viewing eyepiece have a reticle that can be focused with to the eye? If not, it can be critical to the focus process of the scope and camera. There is a physiological function that come into play, in that the depth of focus (i.e. to the eye) and the depth of field ( to the camera image plane) are not the same. The focus to the eye can be accommodated by the eye lens flexing and is particularly a problem when using optics that have a great deal of depth of field. The eye lens flexes, the camera image plane does not. So the object appears in focus to the eye, but not to the camera.

There is a little trick to use during the specimen focus process. Using an eyepiece reticle, focus the reticle while the specimen is slightly out of focus. Once the reticle is in focus, then while focusing the specimen move your head side to side looking through the eyepiece with the reticle. You will notice that while the object is out of focus, it will appear to move in the opposite direction of the head motion relative to the position of the reticle. As the specimen comes into focus, and is matched to the position of the reticle, the object will appear to move in the same direction as the head movement. This will eliminate parallax issues in the focus.
The parallax issue can also be a factor on low mag compound microscopes as well.

ClassMSpecie
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Re: Stereo microscope photo port projection lens not parfocal with eyepieces

#39 Post by ClassMSpecie » Sat Mar 26, 2022 6:21 pm

Good to know. Thank you.

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