Bronica was the first Japanese camera to copy Hasselblad. It was later followed by Mamiya, and Kowa. Bronica's ambition was to allow deeply seated lenses to be incorporated into their camera bodies (for improved lens performance), but they also wished to offer instant return mirror, and it proved to be too complex to accomplish.
Bronica boldly offered unusual mirror mechanisms, i.e., splitting the mirror in two, half going up, the other half going down! In Bronica S (right) the mirror flipped flat at the bottom of camera during exposure. This obsession with mirror design, and having an instant return mirror, couldn’t handle the aggressive nature of professional photography. In real life, the photographer just needs to take pictures over and over without worrying about the mechanical sequence of the camera. A leaf shutter would be the right choice as Hasselblad rightly went for. That critical design decision, later took Hasselblad to the moon.
Bronics S
Zenzuburo Yoshino (Left), the man behind the camera. One of the unique features of Bronica was its mirror mechanism. Bronica insisted on offering an instant return mirror (Hasselblad didn't have this for years), and a mirror design to allow deeply seated lenses.
Bronica didn't use a bellows focusing system. Instead, it had a tubular focusing barrel that was controlled by a focusing ring around the winding crank. They inherited Hasselblad's flat back contour for their cameras, and film magazines (right). Hasselblad's advance gear was designed no to stick out.
In Bronica EC, the mirror was split in half; 85 percent of it flipped up, and 15 percent slided down. Although this would actually counter react to reduce mirror shake, but Bronicas in general produced too much mirror shake during shutter release. My friend, Bob Shell, said I met Mr. Yoshino at Photokina show in Germany, and asked him about his camera's vibration that you could actually notice it in its photos if you weren't holding it right. He said they were working on improving it! The man's fascination with the reflex mirror, and his relentless effort to implement it was phenomenal. Note there is also a small piece that flips up with the mirror to cover the front portion of the focusing screen. In Bronica C, there was a 3rd shutter curtain to cover it!
Mirror operation in Bronica EC, from my book: "Restoring the SLR".
Not an easy Repair !