film advance and spacing

[zumbido]

General question here. In building a medium-format camera on one's own, the most obvious answer to frame spacing is "use a red window".

If a person would rather have a reliable wind-on lever/knob for spacing, where to start? Scavenging the mechanism from a defunct camera is one option. Are there any achievable-without-a-major-industrial-process ways of building one yourself? I can think of a few different ways to implement the decrease in amount of wind-on needed from the start of the roll to the end but none that are that great. I'm apparently not the only one, since so many early cameras have problems with this.

 

[DWThomas]

I believe many cameras use a roller alongside the film gate to meter the film travel, that eliminates the changing spool diameter problem. It does, of course, add some more mechanics.

 

[ic-racer]

I'd use a dark green window for B&W film.
Otherwise, why not just build the camera around an old Graflex (or any brand) 6x7 or 6x9 rollfilm back. It will have the wind mechanism, counter and pressure plate built in.

 

[sv@diycamerakit.com]

If I was building a MF camera and wanted to have a film advance mechanism, I'd use a roller on the film attached to a quadrature encoder driving a small electronic circuit controlling a clutch in the wind mechanism. But I am an electric engineer and I prefer to do things electronically (despite owning a CNC mill... ;-))

I have to warn you though, unless you are building a highly specialized camera (such as extreme pano or rotating), it will likely cost you A LOT more money to build one then to buy a good used one, so I hope you are not doing it to save money...

 

[paul ron]

Build in a Grafloc and use an RB67 back, problem is solved.