C mount lenses were originally designed for 16mm movie cameras. They have very short flange (lens to focal plane) distances, and so were until recently unusable for still photography. With the advent of mirrorless digital cameras, they have come back into demand, as they are mountable and usable on aps-c and micro 4/3 sensor cameras of this type. As they were designed for a much smaller area of coverage–the 16mm film frame–they usually vignette on the larger sensors of mirrorless digicams, but they also often create interesting effects in the areas that fall outside their intended area of coverage. I have a bunch of these little cine lenses, and will lump many of them here, identifying the lenses in the captions.