Introduced in 1983, the Zenza Bronica GS-1 in 6×7 cm format was the largest SLR produced by the company. The camera was designed to be as compact and light as possible, and weighs less than some of the smaller format Bronicas. A lens- or leaf-shutter camera, the GS-1 will synchronize flash at all available shutter speeds. It is a completely modular camera, with several optional focusing prisms and viewfinders (with and without exposure metering), lenses, and film backs. Lenses are designated 'PG', with available focal lengths of 50, 65, 80, 100, 110, 150, 200, 250, 500 mm, and two teleconverters (1.4× and 2×). Extension tubes of 18mm and 36mm are often needed as the lenses are not particularly close focusing. The 110mm is a macro and with 36mm extension tube goes to 1:1. Unlike some other Bronicas the GS-1 never had backs for 35mm film. The GS-1 had a rotary prism that was metered for averaging and spot. The rotary prism made the 6x7 framing for vertical or horizontal very easy. The 6x7 back is landscape and the 645 back is vertical unless the camera is rotated.
With the appropriate back, the camera will shoot a wide range of film sizes, including 6×4.5, 6×6, 6×7 cm, and Polaroid. The 6×6 and 6×7 cm formats could be obtained in either 120 or 220 roll length. The GS-1 was also available with a dedicated G-1 speedlight flash and manually operated speed grip. The G-1 speedlight with the speed grip made the GS-1 the only 6x7 with ttl flash capability (except for the Pentax 67II). The 80mm was the last of the GS-1 lenses introduced and is difficult to find. It equates to a 40mm for a 35mm SLR and is a nice wide standard lens. The 80mm and the 100mm were the two fastest lenses at f/3.25.
Filter sizes are 72mm for the lenses from 65mm to 150mm. The 200mm and 250mm use 82mm filters and the 50mm uses 95mm filters.the 500mm used a 122mm filter The camera was discontinued in 2002.