I knew a man whose colleagues, strangers to me, had managed to attach a 1980s-vintage 3-D lens onto a modern digital cine camera. (I was and am of the impression they were using old ArriVision optics.) These folks did not take into account the fact that their digital sensor size was different from the dimensions of a 35mm film frame, so they were missing vital picture information at the top of one eye and the bottom of the other. In order to make the stereo work, they had to crop like mad, down to a 3:1 aspect ratio. I’m not kidding.
The footage I saw looked like it was meant as a sizzle reel, filmed in all of one day, but it had considerable production value. It looked like the work of real professionals, aside from the fubar 3-D. But these folks would have done well to just take camera and lens down to the beach, or the zoo, or the park and shoot a day’s worth of test footage before hiring an actress and five actors, renting two police cars and a helicopter, and closing off an L.A. street for an elaborate neo-noir crime fantasy sequence, which is what I was looking at. In 3:1 aspect ratio. With chromatic aberrations. And too much parallax.
Depending on the resolution the digital rig is able to capture and the size of the chip. If it's an 8K chip with the same usable area as a Super35 frame, digital over/under would look better than Techniscope, provided there is sufficient light passing through the lenses.