RepRapMicron New Microscope Comparison

I've been looking at a better microscope and found a 4K USB/WiFi one on Amazon AU for NZ$63 https://www.amazon.com.au/Bysameyee-3840x2160P-Microscope-Inspection-Magnification/dp/B09NBY6G9S . It just had to be better than my "Z Axis" one (less than 1MP and ancient) so I got one to try out. There goes a week's beer fund. Here's how my better microscopes stack up excluding aforesaid crappy one. The 4x4 square is 50μm per division and I have manipulated the images to give a pixel-per-pixel comparison at maximum real zoom:

On the left, the trinocular port on my Konus Crystal 45/90 with an 8MP Svbony SV205 image sensor. Quite sensibly, this does not claim a magnification factor (see previous rants on why USB microscopes lie). That can easily make out the 10μm subdivisions, and can resolve down to a micron. It is, however, a great lumbering beast and cost a few thou. 

Middle is the $63 Amazon special. It's quite nice and actually has proper focusing: When you turn focus, it actually focuses the image on the sensor plane rather than shuffling the entire imaging assembly back and forth to hit a fixed focus.

It also has a detachable transparent endcap, so one can get it closer in. 

On the right, the original "decent" Digitech microscope I bought from Jaycar. A reasonable device when I bought it for $300, but now outclassed by the 4K technology. Came with a very nice stand for bench use though.

So why isn't maximum magnification all the time the best thing? Well, two reasons:

 1. With great magnification comes lousy depth of focus, and μRepRap is making 3D structures, not flat microscope sample slides.

Note that I have experimental implants in my eyes with infinite focal depth on the macro scale. This means that when using a binocular microscope I get a radically better depth of simultaneous focus than most people, but I can't take pictures of exactly what I see, and few others can see what I do. It also means my Svbony imager focus almost always needs tweaking before I take a photo.

2. Doubling the resolution quarters the amount of available light. Adding more light only works up to a certain point, then you have a small sun on your workbench and your samples melt. 

Next step is to try the 4K out on imaging the probe as it closes in on the glass slide, and see if I can use that image to get the probe within a few microns of it. The old <1MP microscope was obviously not capable of doing that. If it works out, I'll get another.