I’m not sure I understand the question. If you’re using a projector you can build a “projector telecine” that involves removing the shutter, putting in a good LED light and then pointing a camera at the gate. Past designs used video cameras which weren’t very good, but you can get very good quality machine vision cameras now which aren’t that expensive. If you’re using a projector you just put a small magnet on a gear that rotates once every frame and use a hall-effect sensor to trigger the camera (see this diagram). You can capture at realtime (24fps) or even faster using that method, but that will also depend on the choice of camera the resolution and the data speed. Negatives have a thinner base compared to prints, but a decent projector should still be fine handling negatives in decent condition as your transport.
Beyond that most modern scanners ARE just a camera pointed at the film at the heart of it. There’s a bit more involved, this shows you how the Filmfrabrik scanners work:
And this is just the stuff that’s in the direct line of the camera:
That part is exactly the same design that’s in the Lasergraphics Scanstation and the Blackmagic Cintel. Camera, Lens, Gate, Integrating sphere/cube to diffuse light, RGB LED light, heatsink.
Welcome to the community!