Were any of you former Bronica engineers? I have a question about the SQ cameras.

reddesert said:

I'm not a former Bronica engineer, but I have a pretty good guess.

The Bronica ETR/SQ/GS cameras are not directly comparable to the 35mm cameras you're used to because these Bronicas have a in-lens leaf shutter, while the 35mm cameras have a focal plane curtain shutter.

In an electronically controlled leaf shutter like the Bronica's Seiko, there are no mechanical delay timers. The shutter has a spring that fires as fast as it can go, and the electronics have a delay timing circuit that holds the shutter open. With no electronics powered, the shutter is undelayed and fires at its fastest speed, 1/500. It will still X-sync at that speed, since it's a lens shutter.

In a focal plane shutter, the timing is of the second curtain firing. It can be delayed a little to start before the first curtain finishes, so you get a traveling slit and the speeds faster than X-sync. Or it can be delayed a lot and you get X-sync speeds and slower. In a mechanical shutter, this is done with usually two timing mechanisms (fast and slow). In an electronic shutter, it is likely one timing circuit, but for a mechanical backup, the second curtain can be mechanically tripped by the first curtain completing its travel, which gives you the X-sync speed.

So I think the main design goal is mechanical simplicity of the backup, although enabling X-sync is a useful capability. Many electronically timed cameras don't have a mechanical backup speed at all (eg Mamiya M645, many 35mm). The backup is to carry a spare battery.

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MattKing said:

FWIW, the Mamiya 645 Super has a mechanical backup speed of 1/60 for its focal plane shutter.
That camera's replacement, the Mamiya 645 Pro replaced that functionality with a self timer function.

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