I'm looking at building my own 12x20 camera in the not too distant future, and thinking about what I can do for a shutter. Would it be possible/workable to use the focal plane shutter out of a Speed Graphic (either 4x5 or smaller) as a behind-the-lens shutter?
Hello Scott!
Some reactions for you. I am sure the fps from a Speed Graphic would work. And it would give you a range of accurate/dependable shutter speeds, assuming it was tuned up properly. I would imagine a lot of tinkering and imaginitive engineering would be involved. If you enjoy building and designing it would be a great project.
That said, if the goal is aimed more at producing large negatives in that wonderful format, what about a Packard shutter? Simpler to install and very useable despite the lack of shutter speed options.
Keep us all posted on your progress. Lots of really great folks in this forum who have a whole lot to offer.
Good Luck!
I'm certainly going to use a Packard shutter - I'm just thinking in terms of something that would give me a wider range of predictable shutter speeds. Given the lens I'll have to use with the camera, there may not be any real need to compensate for the difference between the use as a focal plane and the use as a behind-the-lens shutter (most of the 600mm+ lenses out there have 3"+ diameter rear elements).
Domenico Foschi (www.dfoschisite.com) did this as a way of using big, fast lenses wide open in daylight. He used a 3.25x4.25 Speed, as they are available cheap because of the orphan format. Search for threads here and at photo.net in which he describes the system and how it works.
There are issues to do with potential vignetting and shutter "efficiency", but in practical use, if I remember right, it just works.
If you want to test the idea without hacking and chopping, you can probably just remove the ground glass and G-clamp the whole Speed Graphic to your front standard.
It has been done. I don't remember if I read it in posts here, photo.net, or APUG. I think there was some discovery about angle of view influencing the effective shutter speed. (which makes sense.)
The big speed graphic FP shutter has inertia that might shake the camera. Yep, the Packard is the way to go.
Scott, based on the behavior of my two Speed Graphics, I believe that the shake would be too much at the faster speeds, especially out on the end of the camera. Also, while the FP shutter of most SGs is pretty accurate, sometimes uneven exposure can happen if it drags a little. The other part is that unless you find some very fast film, chances are good that you'll be using slow speeds much of the time. Unless you just want to experiment, the Packard sounds best. Also, there were some obscure rolling type shutters to mount in front of the lens that work in a similar way to the SG's FP shutter. I think Glennview.com had such as device one a little bit ago, although I don't know how it works or much about the vendor.
It's not nice to gut a working Speed for any reason. That said:
Another consideration. If you mount the shutter behind the lens, or any distance away from the film itself, the spedd changes in proportion to the distance away from the film. It's a moving slit. At the film plane, the slit moves 4 inches. If you mount the shutter behind the lens, it will still be moving 4 inches, but you're illuminating a 12 inch film plane. Think of a lever. You would have to recalibrate the speeds with a shutter tester, and those speeds would only be valid at that particular distance from the film plane...
Then there's the shake. The graphics are either hand held or tipod mounted right at the point of the FP shutter. If you move the shutter out tot he lens, well, think of a lever...
Go with a Packard...
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