Directors View Finder
These Directors Viewfinder uses optics from old 35mm film cameras housed in 3D printed enclosure. Each unit will be different from each other since many of the optics are from different SLR cameras with different designs. As such each viewfinder is listed individually and noted with any defects on the used optics.
Inserts can be fitted in through the front that basically frames up for the actual sensor size used. So with this directors viewfinder, you can see exactly what you'll see in frame as you would on the camera.