DSLR, or mirrorless? (And a question about mirrorless adapters)

[kwesi]

I work as an educator and I'm going to be running some high-school workshops, where we'll look at compost and soil under a compound microscope (brightfield and darkfield, up to 40X objective) and possibly use a stereo microscope to examine mosses, lichens etc. To test things out I've been bringing my personal compound scope and Nikon D3400 to work, and now it's time for my workplace to purchase its own equipment. I'm likely going to be puchasing an Amscope T490B trinocular compound microscope (and possibly one of their trinocular stereo microscopes), as well as a digital camera.

I need to be able to connect a camera to the microscope and to a projector for live viewing in the classroom while capturing photos and videos. Bluetooth would be a useful feature, both for sharing images wirelessly and for remote control of the camera with a smartphone. I don't care whether the images produced show the entire field of view with a black circle around the image, or whether the sensor crops them to a rectangle. I don't think I want a USB microscope camera as being able to use it for non-microscope things will be useful.

I'm wondering if my workplace should buy a DSLR or a mirrorless camera? What are the pros and cons of a DSLR like a Nikon D3500, vs a mirrorless camera in a similar price range like the Canon M50? I'm familiar with the DSLR + microscope setup but haven't used a mirrorless camera before.

I also have a question about setting up with a mirrorless camera if I were to go that route. For my home setup I use one of Amscope's DSLR adapters, that uses an F or EF-mount T ring and a 2x coupler that fits the scope's photo port. For a mirrorless camera, could I buy the same adapter and then just buy an EF-M-mount T ring to attach the camera body to the 2x coupler? Or do I need to buy an EF to EF-M adapter because of the different flange distances? The photo port that comes with the Amscope is adjustable vertically; will this let me achieve parfocality between the eyepiece and the camera regardless of the adapter/flange distance? If the Amscope DSLR adapter can't be adapted to fit a mirrorless camera, could I get a link to somewhere I could find a mirrorless adapter that isn't too expensive? (The only ones I've found cost more than the microscope). Thanks in advance!

[imkap]

I think a mirrorless is better, especially for live view. If you want to use it in the classroom for projection, look that you get one that can work while being plugged and charging, although you can get a dummy battery for any model, but the other variant is simpler.
As for the adapter, the mirrorless must be a few cm further away from the lens (microscope), because they don't have a mirror. But not sure how you'll setup everything, so it might work ok either way.
My friend owns a Canon M50, it is great, I have a Sony it is also great.

[kwesi]

As for the adapter, the mirrorless must be a few cm further away from the lens (microscope), because they don't have a mirror.

Oh okay, so it's specifically the objective lens that the sensor has to be further away from, not the lens in the 2x coupler? That's one of the things I wasn't sure about

[PeteM]

The 2x photo relay lens that AmScope sells to project an image somewhere between APS-C and full frame sensor sizes isn't an especially high quality bit of optics. It's usable, but not much sense IMO in putting it in front of an expensive DSLR or mirrorless camera yet to be bought.

One suggestion would be to get an an affordable microscope with a C-mount trinocular head and attach something like a Nikon J-1 mirrorless camera body to it. The camera should do fine for your purposes, will perform better than most USB eyepiece cameras, and shouldn't be more than $150 or so. With a reduction lens in the C-mount, something like a Sony Nex 5N mirrorless body could be even better and still affordable.

Wider field infinite objectives can also directly project to APS-C sensors and usually not look too shoddy around the edges.

As for the stereo microscope, most of these take pictures by diverting all the light from one side of the optics to a camera. If you want to simultaneously manipulate something in a stereo view while projecting a video image, you'll want the type of adapter that steals about 50% of the light for your camera.

What you might find works best for the lichen etc. is to equip your compound microscope with something like a 2x objective and a condenser than can cover its field. You video camera isn't going to catch a stereo image anyway - and the optical quality of a decent 2x objective (20x or so at the camera) is likely to be better than a 2x objective set off to the side on a stereo microscope. Your camera in macro mode could likely stream an image if anything you wanted to show at less than 20x?

[PeteM]

A question in return. I keep running into people who want a microscope to study soil from large scale (say, worms) through fungi and protists down to the level of bacterial counts. Any chance you could tell us a paragraph or two - or point to a resource - that explains how what one sees in the soil turns into practical suggestions for improving it?

[imkap]

As for the adapter, the mirrorless must be a few cm further away from the lens (microscope), because they don't have a mirror.

Oh okay, so it's specifically the objective lens that the sensor has to be further away from, not the lens in the 2x coupler? That's one of the things I wasn't sure about

I didn't say that...

Dslr adapters are shallow

Mirrorless adapters are deeper:


For the same distance to the sensor, because mirrorless does not have a mirror...

[jfiresto]

.

[blekenbleu]

The photo port that comes with the Amscope is adjustable vertically;
will this let me achieve parfocality between the eyepiece and the camera regardless of the adapter/flange distance?

Some photo ports are short enough for e.g. a video sensor to be directly focused from finite objectives or (infinity objective) tube lens.
For those ports, a mirrorless camera with a thin adapter may also focus for direct projection, without relay optics,
where an adapter that adds DSLR spacing may not, thus requiring relay optics.

[kwesi]

The 2x photo relay lens that AmScope sells to project an image somewhere between APS-C and full frame sensor sizes isn't an especially high quality bit of optics.

Thank you for the detailed reply.
I'm not especially worried about the reduction optics being the highest quality, I've used Amscope's version for this application before and was able to produce images at a suitable quality for teaching students.

Part of the reason I'm looking to buy a newer camera vs a cheaper one like the Nikon J1 is for the off-microscope functionality. There are features like Bluetooth, GPS, an articulating screen etc. that will make a lot of things easier in other settings. A lot of my work involves cameras, only part of it involves microscopes. Also this initiative is funded by a grant focused on innovative uses of technology, so even though at home I'd go with the most economical options, opting for more high-tech gear (within reason) will actually help secure more funding for the program.

For the stereo microscope, I don't need to use the eyepieces while projecting, it will be fine to just go off the screen even with the bit of latency that introduces. I like the idea of using the compound scope with a 2x objective, but the condensers on the student-level scopes I've looked at don't cover that large of a field, and they don't appear to be interchangeable. I'd also need to set up a reflecting light source and there's not much space under the head of a compound scope for that. A stereo scope makes sense for me because having the flexibility of letting the students look at the stereo image themselves sometimes could be useful. I'm hoping to find equipment that has fairly wide ranges of use, as my coworkers will also get to use it for their projects and having more flexibility will be beneficial.

[PeteM]

Wild (now Leica) made stereo microscopes (M3C, M3Z) with an option to shift the bottom objective to the center of an eyepiece for improved imaging. Including an intermediate piece to attach a camera, you might find one of these around the $500 range used. They're beautifully made, have decent imagine quality, and are more robust and easier to maintain than the typical import stereo microscope. One of these might be a good candidate for digital projection to a classroom, if your grant permits buying used gear.

[kwesi]

A question in return. I keep running into people who want a microscope to study soil from large scale (say, worms) through fungi and protists down to the level of bacterial counts. Any chance you could tell us a paragraph or two - or point to a resource - that explains how what one sees in the soil turns into practical suggestions for improving it?

Sure, essentially what I'm doing with high school students is all qualitative. We aren't doing any cell counts, just examining different soils as a jumping-off point to discuss soil communities, and looking for evidence of diversity in taxonomic groups which would suggest an intact food web and effective nutrient cycling. So for example we might look at regularly heavily tilled soil, and undisturbed soil, and notice that the disturbed soil seems to contain fewer fungal hyphae. We could then discuss how tilling keeps soils in an early successive state, where organisms like bacteria may dominate as "higher" taxonomic groups like multicellular fungi get disrupted. We could also look at the relative size of the soil aggregates in the two soils, and discuss how aggregates form and their importance in soil stability.

Or we might discuss whether we expect to find more microalgae near the surface of the soil or deeper down, then check that hypothesis and discuss algae's role in nutrient cycles. We usually also observe ciliates and microanimals like rotifers actively feeding on single-celled organisms, which is always fun to see and really brings the food web to life. You can also sometimes make out nematodes' mouth parts, so for example if you see a bunch of fungal-feeders that indicates the presence of living fungi even if you don't see the fungi themselves.

What this all boils down to is communicating to kids the basic ideas most of us already know - that to keep nutrients cycling its good to have biodiversity in the soil, and the way we try to support that is basic stuff like mulch with organic matter, till minimally, don't pollute, add compost, avoid over-compacting, etc. Because soil microbe communities are unfathomably complex and constantly changing, there isn't much use in someone like me looking at soil and trying to diagnose specific issues. Maybe it's possible with a lot of other context clues, for example consistently finding an overwhelming number of ciliates and no other protozoans could indicate anoxic conditions, and if you notice that the soil is regularly waterlogged and plants that like anoxic soils are thriving there that might also hint at that. Whether that's a good or bad thing comes down to context as well. And again most of the time your best shot at supporting soils is the basic things mentioned above. Hopefully things become less obscure the more young people we can encourage to get into soil science.

[kwesi]

if your grant permits buying used gear.

Thanks for the suggestion! It's tough with used gear, since I have to be specific about what I'm buying and there's enough time between application and approval that what's on the used market could be totally different. Good to keep in mind for my own home lab though.

[imkap]

There are dealers of refurbished used stuff.

[sreynolds]

I can clarify the answer to the question about adapter thickness by reference to https://briansmith.com/flange-focal-distance-guide/ which is just one good source of information that I came across. Different cameras/lenses have different flange focal distances. This is the distance from the lens mounting flange to the location of the image produced by the lens, and therefore the position of the camera sensor. SLR's typically have longer flange focal distances - in the case of the Canon EF mount, it is 44 mm. Mirrorless cameras typically have shorter distances - the Canon mirrorless system EF-M is 18 mm. It is common to use Canon EF lenses on Canon mirrorless bodies with an adapter which pushes the lens out from the mirrorless camera (44 - 18) 26 mm. This mirrorless adapter is thick. A C-mount lens (common microscope adapter) has a flange focal distance of 17.526 mm - and so, using a C-mount on a mirrorless Canon body requires the adapter to be very thin, actually putting the flange of the lens just inside the camera body. Adapters have limitations based on the lens being used - while it is common to use old SLR lenses on mirrorless bodies because you can space them away from the mirrorless body, it is not possible to do the opposite - use a mirrorless lens on an SLR because of the short flange focal distance of the mirrorless lens.