phenolic composite selection

Years ago, we used the linen filled type pretty regularly for miscellaneous bits.

FWIW, the CTE of laminates like the common G10 (epoxy-glass) is quite decent along the X and Y axis, but much, much worse along the Z axis, due to the lay of the glass fibers.

Hey, you could stack 3 layers of 1/8" PCB material. Would be pretty cheap to have made, including printing.

did you have any problems with it sagging and warping?

good call. glass filled pcb is flat and stable enough. I should shim the ground glass into place instead of trying to cut into the fiberglass itself.

Depends on the thickness of the PC board. There are really thin types that are made for building up into multi-layer PC boards that are about as flexible as light cardboard. And most of the do-it-yourself view camera plans I've seen rely on shims to get the ground glass into the same plane as the film. My Graflex has card shims under the main viewing ground glass edges, don't know if they're original, wouldn't surprise me if they were. They're stuck down with shellac or gasket cement. Not sure how fancy you have to be with a focussing panel, Graflex used straight-grained mahogony in their cameras and there are thousands that have outlived their original owners and are still quite usable. Unless you use a vacuum film holder, your film isn't going to be perfectly flat anyway, it'll always have a bit of curl to it at the edges, normal stopping down takes care of that problem. And there's going to be tolerances between film holders and thickness variations between makes and types of film as well. So getting things down to a hundred-thousandth is kind of futile. Don't over-think the problem.

Stan

I'm making a ground glass holder that's exactly the size of a standard 4x5 cut sheet film holder. It only needs to work facing one way and will be notched along the edges to also emulate an international back. I want it to fit any of my existing cameras. I've never heard of such a "univeral" ground glass, so that's why I want to build this. I can add one of those fresnel sheets later if needed and only have to buy one.

It turns out there's no real standard for film holder edge to film surface distances no matter what anybody on the internet says. Even the alleged ANSI specs seem seem as random as the measurements I've taken from Fidelity cut sheet holders, various ground glasses and original Graflex roll film adapters. It obviously makes sense to just copy the distance from a loaded sheet film holder if thats what'm going to use capture the images anyways.

I have a 50+ year old Crown Graphic which I use. It's less gadgety than the German equivalents, and far more usable. The rangefinder light fascinates everybody. I think Polaroid was the last company to make cameras with that feature (on their medical macro camera).

If it can approximate the quality of the Crown Graphic parts, I'll be quite pleased.

I don't recall any, but it wasn't that kind of application.

The Graflex back was about as "universal" as it got during the early days of the last century, focusing panels could be swapped between cameras and film holders were pretty close for tolerances. The only problem with the Graflex back was that it was SLOW to use, something newpaper cameramen that adopted the Graflexes and Graphics didn't appreciate. Had sliders to lock components to the camera. So the spring backs and the much later Graflok backs were invented. Those were both good enough for news snapping and a lot faster to change holders. The Graflok has morphed into the standard back for most current large format cameras. A Crown Graphic could be ordered with either a spring back or a Graflok at one time.

I've used thin Baltic birch plywood glued up and machined for Graflex/ Graphic/large format lensboards and optical mounts. Has worked fine.

Stan