Like most medium format cameras, the Bronica ETR System includes interchangeable film backs (or “magazines”), with a range of different film back types supporting different types of film. Four generations of film backs were produced, released with the ETR, ETRS, ETRS Mk-II and ETRSi models, each bringing a number of small improvements to their functionality.
Components
ETR System film backs (except for Polaroid film backs) are comprised of three sub-components:
- Film Back Frame, which attaches to the back of the ETR camera body (for the 70mm film backs, the frame is two separate components)
- Film Holder (or “insert”), which holds the film and is inserted into the film back frame
- Dark Slide – which protects a loaded film from light exposure when the back is removed from the camera, allowing backs to be interchanged part way through exposure of the loaded films

All types and generations of film backs are compatible with all generations of ETR body. The exceptions to this are the ETR-C and ETRC bodies, where the film back frame is fixed to the body (although it is possible to switch between 120 and 220 inserts within the fixed back component of the camera). However, ETRSi generation film backs are the easiest to operate and most recently manufactured, making them the better choice where possible.
In some cases, it is possible to combine different generations of the three sub-components to form a complete back – for example, an ETRSi generation 120 Film Holder can be put into an ETRS Mk-II generation 120 Film Back Frame, with an ETR generation Dark Slide. Because of this, care must be taken when purchasing a back to understand which generation each sub-component of the back belongs to, as many have been mixed and matched over the years.
Film Back Types

120/220 Film Backs
These films allowed 6×4.5 cm exposures on either 120 (15 frames) or 220 (30 frames) roll film, and were the default backs designed to be used with the ETR System.
135 Film Backs
By using these backs, the ETR could be converted to a 35mm camera system, allowing both normal sized and panoramic exposures on 135 film.


70mm Film Back
The ETR System was know for its popularity amongst wedding photographers, and this back allowed the use of 70mm film to reduce the number of film loading breaks needed.
Polaroid Film Backs
Polaroid Land Pack Film backs allowed the photographer to immediately test the exposure of a shot before committing the image to film.
