c-mount

Here we have a couple CCTV lenses using the C-Mount 'standard': Computar 12.5mm F1.3 and Canon 12.5-75mm F1.8. Even though both are made for 1" or 2/3" (respectively) format video camera, they can be used on Micro 4/3 camera, such as an Olympus E-PL1, via an adapter. Aside from being bright and fairly wide, both lenses vignette quite a bit.