Imaging with stereo microscope

[Elapid]

Some time ago I purchased a Unitron Z650HR stereo microscope with a small digital camera attached to the trinocular tube. I bought it specifically for viewing and photographing biological specimens such as fungi, insects, plant parts etc. I’m satisfied with the scope for viewing and doing some dissection but for photography I find the magnification the camera produces is unacceptable. Even though the camera has a 0.75x lens attached it effectively doubles the magnification of the scope and reduces the field of view by a proportional amount. In other words the camera captures a rectangle in the center of the FOV that has area less than half the area I see thru the eyepieces. Neither the dealer nor the manufacturer were any help, the more magnification the better they say. I decided to attempt to adapt my full-frame DSLR to the scope after removing all of the phototube that could be removed. I was able to locate an intermediate image plane about 10mm above the trinocular port and I machined an adapter that allows me to attach the DSLR with a 1.6x teleconverter. It’s not quite parfocal but produces acceptable images except for one crucial problem. There is flare which casts a fog over the central part of my images, in other words an internal reflection which is cast up into the camera. This ruins the image because contrast is severely degraded over much of the image and a white cloud is visible over each image. This does not happen with the tiny camera that came with it. After some trial and error I localized the flare to the trinocular port itself, there is no flare visible with the eyepieces. Looking down into the camera port I can see light reflected up from brass pieces down in the port. So I thought I’d use some flat black paint or black paper to eliminate the reflection but I discovered that I was actually seeing the reflection in a prism, I couldn’t reach the area where the reflection was occurring. There is no apparent way to disassemble the scope enough to reach the brass pieces causing the reflection. Changing the external illumination type and direction doesn’t correct the problem.
So I’m considering either attaching my DSLR to an eyepiece port or just looking for a different stereo zoom scope. If I were to purchase say a Nikon SMZ-2 or SMZ-10 with trinocular head would I still have the problem of only capturing half the FOV with the camera? Would such a scope be prone to internal reflections if I removed the phototube and machined an adapter to capture an intermediate image just above the scope? Or should I stick with the Unitron and try to do eyepiece imaging?

[PeteM]

Lots of options.

Shooting afocal over an eyepiece. Clumsy, but you may already have everything needed.

Using a cell phone camera, ideally with a previous generation phone camera, a holder (cheap), and a spare eyepiece permanently attached so taking photos is fast. You can get a right-sized image and likely better resolution. Given the cell phone camera (something like an iPhone 6 can be excellent), you just need a $20 or so holder, a $15 remote release, and maybe another $45 eyepiece.

Get something like the SMZ-10 and use either the OEM 2.5x photo relay lens for full frame cameras or other options discussed in past threads. Bigger $$$

Switch to a good mirrorless camera body with a smaller sensor and a C-mount adapter with an appropriate magnfication factor. Nikon J1 is what the industry calls 1" sensor (it's smaller). Lots of affordable but good MFT and APS-C options. The goal would be to keep the image circle well away from the flare you're currently getting. Maybe $200 for a lightly used earlier generation camera body and $100 in adapters. The camera can be dedicated to the scope (trinocular?).

[Scarodactyl]

Now you know why the trinoc port has to crop so mich--the adapter must be acting as a baffle tk rempve that stray light. This is poor engineering, not necessarily surprising on a Chinese scope (which are often simplified copies of other designs) but disappointing on one in this price bracket. This isn't an issue I've run into with Nikon trinocular stereos.
You can usually capture a reasonable portion of the FoV with a Nikon stereo. The smz-10 actually has a reduction lens in the trinoc port light path which widens the FoV.

[Elapid]

Thanks very much both of you. I know some people get excellent results with a cell phone on an eyepiece and that should work for me because the flare does not show up when viewing thru the eyepieces, only when using the trinocular tube. I can even see where it’s occurring in the brass parts of the tube but it can’t be reached because it’s only a reflection of the lower tube in a prism. I think the idea is worth a try.
Yes, it has occurred to me that the manufacturer limits the FOV captured by the camera they supply because of the flare. However the flare does seem to be central and their camera system gives images with less contrast than I expected and it’s possible that flare is the culprit but it doesn’t look like flare because everything else is cropped out.
I wasn’t sure how much of the FOV is captured by a SMZ-10 or simular scope but you seem to be saying that it would be much more that I get with my Unitron so I’ll look around for a deal on one.
Thanks.