Topic: How Bronica backs work!

[Terry]

I had a messed up back for my Etrs so I decided to dismantle it and figure out how the back talks to the camera.  I had read that it was electrical, but it's not (and it's pretty clever too).  Here are some pics with text.

On further pondering I figure that the back repeats step three for each frame, so the camera knows when to allow the shutter to fire. 

[Francois]

Well, that is pretty ingenious and simple...

[Terry]

Emboldened by yesterday's results, I opened up a back from my SQ and realized that, although it looks a bit different and the gears and levers and tabs and such are in slightly different places, the function design is the same.  If there's any interest I'll post photos of the SQ too.

[Terry]

Well, I did it anyway; had to find out what's inside the SQ back!

Here it is for the SQ back.  The function is just the same although the parts are shaped differently:  When you load the film, it gets pulled tightly over the top (larger) roller.  When you put the insert into the back and close the cover, it pushes a metal tab that engages the gear attached to that top roller with a train of gears that were spinning loosely but are now connected to the frame counter mechanism (because you closed the cover).  Closing it also pinches the film between the large rollers (on the insert) and two very thin rollers in the outer body of the back (just behind the dark slide).  This ensures that the film will rotate the large top roller precisely as it advances.  As you crank the winding handle, two things happen: you tell the camera that there is film in it (the pin at the bottom of the back engages with a pin on the body of the camera) and you tell it when you have arrived at the first frame and are ready to make the first exposure.  Very simple and clever and yet requiring accurate gearing.

[jojonas~]

interesting! I'll make sure to send a link to this topic to a club member that just got a SQ this summer in case he'll need it

[Terry]

I've had my Bronicas for a couple of years and always wondered how the camera seemed to know if there was film in the back or not.  I searched the web and didn't find the answer (or I found answers that just seemed silly to me), so I did my own research. 

[Skorj]

Great stuff!

[johnha]

Thanks, might help me out if I have any problems with mine. Might be simple & elegant to some but looks quite complicated to me.

[Terry]

Compared to, say, an Exakta!

[mcduff]

This is all pretty cool, and props to you Terry for being curious! 

You say you are an ETRS owner. I am thinking of entering the 645 world and keep being drawn to this camera. Despite the fact that the back messed up, you like this system? If I go 645 it is probably either this or the mamiya system (I like pentax systems but the pentax 645 with the built in powerwinder may be too space aged for me). Not to hijack this thread into a more general talk about this system...

[Terry]

Hello McDuff!  I should clarify about that back--I got it in a lot of Bronica stuff and it looked like it had been worked very hard by someone.  So it was not working when I got it; the working backs I've acquired have all continued to work.  The whole system is pretty robust, even the one plastic body I've got (which I've read that you should avoid).  I like the weight and size of the ETRS and I like the Seiko lenses a lot.  The camera is pretty ergonomic: the controls are where I want them to be, the crank winds quickly and easily and the waist-level finder is a pleasure to use.  The SQ is a bit bigger and heavier, but I find I use mine fairly often too.  But the ETRS really gets a workout--the light weight and the 15 frames are nice benefits, and I like the 4.5x6 format.  I've never shot the Mamiyas though--my only other similar camera was a Kiev 88!  I like the ETRS a whole lot better than the Kiev!

[johnha]

Hi mcduff. I've got both a Mamiya 645 (Pro SV kit) and Bronica SQ-B (I guess similar to the ETRS). My assessment is that the Mamiya is more integrated and less 'clunky' (e.g. it has an instant return mirror unlike the SQ-B), especially the 'Pro' models. My Mamiya has a 1/1000th top shutter speed with a focal plane shutter - Bronica 1/500th leaf shutter. Mamiya lenses seem cheaper & faster (no shutters) whereas I've had to return a couple of used Bronica lenses because the shutter speeds were wildly inconsistent. For 645 you almost certainly need a prism for vertical shots.

I used (occasionally sill use - much to the surprise of the d*****l brigade) the Mamiya for photographing aircraft quite happily, doubt I'd be able to do this with the Bronica.

Having said the above, I prefer the Pentax 6x7 to either at the moment.

[mcduff]

Thanks johnha. Thanks for the information. I have access to a Pentax 67 that I can buy and likely will at some point. I do like the 645 format for its aspect ratio, 'compact' size and economical film use. If the Pentax 645 was just a scaled down Pentax 67 that would probably be my dream mf camera. I think I am going to head down the mamiya 645 route but can see my having a 67 and 645 eventually.