View Full Version : A Couple of questions about shutter dimensions

20-Nov-2006, 12:49
Hello, this is a beginner's question but I am having a hard time understanding some of the details on this webpage (http://www.largeformatphotography.info/shutters.html) about shutters.

For example this table should be simple to understand:

dimensions in mm Copal 0 Copal 1 Copal 3
1/board mounting thread M32.5x0.5 M39x0.75 M61.0x0.75
2/flange ring diameter 34.6 41.6 64.0
3/board hole diameter 34.8 41.8 64.2
4/front lens cell thread M29.5x0.5 M40.0x0.75 M56.0x0.75
5/rear lens cell thread M29.5x0.5 M36.0x0.75 M56.0x0.75
6/front to rear cells flange 20.0 +-0.025 20.0+-0.025 28.6+-0.025

I can understand most of this but what is the flange ring diameter? I can't seem to figure it out.

Also, I what is the difference between an ordinary shutter and a press shutter. Why are they better for multiple exposures? Is it just the additional shutter cocking step that is eliminated?

Finally, I have been leaving my bag in the boot of my car and it seems that a couple of my shutters are dragging at the slower speeds, about a 1/4 sec and more. Is this normal with cold temeratures? If I want a shutter adjusted for these speeds, how much should I expect to pay - any recomendations for such repairs would also be appreciated.

Thanks for any help,

20-Nov-2006, 13:42
flange ring diameter is the diameter of the hole of the ring/nut that screws on and holds the shutter on the board.

With press shutter you don't need to manually cock the shutter before pressing the release. The cable release does both the cocking and release. Because you don't manually cock the shutter, you don't move any parts of the camera, therefore, it keeps the image registration during multiple exposure.

Yeah, some of my copals and supermatics got slower in the cold. Flutot seems the place for shutter repair, probably about $50.

Doug Kerr
20-Nov-2006, 14:09
I can understand most of this but what is the flange ring diameter? I can't seem to figure it out.

I would expect that "flange ring diameter" refers to the outer diamater of the little collar that extends from the actual "flange" of the flange. This is what has to go through the hole in the lens board.

Best regards,