by 1974, the autoexposure slr brands had aligned into two camps (shutter-priority: canon, konica, miranda, petri, ricoh and topcon; aperture-priority: asahi pentax, chinon, cosina, fujica, minolta, nikkormat and yashica) supposedly based on the superiority of their chosen mode. (in reality, based on the limitations of the electronics of the time and the ease of adapting each brand's older mechanical designs to automation.) these ae slrs were only semi-automatic. with shutter-priority control, the camera would set the lens aperture after the photographer chose a shutter speed to freeze or blur motion. with aperture-priority control, the camera would set the shutter speed after the photographer chose a lens aperture f-stop to control depth of field (focus).