Then this is my ridiculous machine based on a 3D printer board that blows through whole carts of slides at a time. Same lens/camera/backlight as before though.
For this one, it's a Pi again, but I used tethering instead as there's a webcam in there for capturing the front of the slides at the same time for automated labelling. libgphoto worked but was a bit flaky (once it started working, everything was fine as long as I didn't touch any menus in the camera)

I forgot to mention the lens: Sony 50mm macro. It's a really good macro lens, but it's not a great prime because the electronic focus is so slow