The camera capabilities of the Raspberry Pi took a pretty big leap forward when they released their new High Quality Camera module last year. The then-new module allowed you to finally get full manual control over your exposure, but it also lets you attach CS and C mount lenses (or just about anything else with the right adapter).
It was only a matter of time before somebody built it into a “real” camera form factor, and it actually didn’t take long, as this film-to-digital conversion shows. But now a new project has popped up. RUHAcam. It’s a 3D printable retro-looking camera based around the Raspberry Pi Zero W and it operates just like a regular interchangeable lens digital camera. Kinda.