A medium format 6x4.5cm film SLR system that offered high quality performance, handling convenience and versatility required for professional photography. It consisted of 5 models of the ETR series:
- ETR - Bronica's first lens shutter SLR camera with interchangeable lens, film back, finder and focusing screen systems;
- ETR-C - a ETR with the only major difference that the back was not removable, but used film inserts;
- ETRS - an improved version of the ETR with the interchangeable viewfinder system (new AE-II & III finders);
- ETRC - a ETRS without the interchangeable back system;
- ETRSi - an improved version of the ETRS with mirror lockup, bulb mode, TTL flash metering with OTF flash exposure, and improved advance mechanism.
The ETR series cameras were developed as complete modular system cameras, with a very high degree of interchangeability in lenses, finders, focusing screens, film backs, plus a full range of other valuable accessories which permitted their use in many other day-to-day assignments, requiring a fast-handling camera with complete exposure automation. They offered the handling speed of the 35mm camera, but with the advantage of the 6x4.5cm frame size.
A wide range of lenses from the 30mm fisheye to the 500mm super telephoto, plus macro, shift and zoom lenses, were available in the system. The very compact lens designs incorporated a Seiko #0 between-lens shutter, with the electronic control mechanism in the main camera body, which also provided full flash synchronization at all shutter speeds up to 1/500 sec.
The ZENZANON lenses for the Bronica ETR system can be divided into three series:
- The MC series - the first generation, multi-coated (hence "MC" on the front ring), first with a silver ring at the front (40, 50, 75, 150/4, 250mm models for the ETR and ETR-C), later without a silver ring. Aperture adjustments in full-stop increments. Listed as "ZENZANON E" lenses in the manufacturer's literature;
- The E II series - totally new optical designs similar in exterior to later MC lenses (it seems that Bronica at some stage decided to abandon the abbreviation "MC" in favor of "E");
- The PE series - the next generation that took full advantage of MTF technology in their design, and had overall improvement in optical performance. Offered aperture adjustments in 1/2-stop increments.
A number of E and PE-series models were also designed and produced by Schneider-KREUZNACH in Germany.
Regardless of generation and manufacturer, all ZENZANON lenses for the Bronica ETR system cameras were noted for their high image depiction characteristics and superior color balance.
In 1995, lens manufacturer Tamron acquired the Bronica camera business. Four new PE lenses were soon introduced, however, with the advent of digital photography, medium format sales declined at a rapid pace, and for Bronica, that slip was faster since their core customer base - portrait and wedding photographers - adapted well to digital SLR equipment. On October 1, 2004, Tamron announced the worldwide discontinuation of Bronica SLR cameras and accessories as of October 31, 2004.