The main differences between BC1, BCA and B100, B200 are the viewer indicators (for example, the shutter speed is shown by a needle in B100, and diodes in BCA), and a new flash shoe with a supplementary contact for coupling with Olympus-compatible flashes (no TTL, but in automatic position, the camera passes to "flash-synchro" speed, with a new diode lit, when the flash is loaded). Externally, there is a new film speed setting knob, made of plastic, easier to use.