Various c-mount lenses can be used with adapters on the Panasonic G1. Some of them work well, others not. Generally, lenses made for so-called 1" CCTV sensors cover all or most of the G1 sensor, with some vignetting. cs lenses don't work, won't focus. Of other small format lenses, 16mm movie camera lenses work pretty well, old Pentax 110 SLR lenses work and lenses made for the Olympus Pen F cameras work.