If you were to unknowingly or erroneously (I've seen someone do it when reassembling a camera) put the ground glass in backward, ground toward your eye, and not toward the lens), you could still see and focus.
However, what happens with the thickness of the glass between the lens and the ground glass image is that the focal point is set further back...there is an equation for a flat glass element (some lenses include them, patent for Metrogon or maybe Topogon covers this, also discussed in photogrammetry books I unloaded onto someone else), with resultant focus shift IIRC = t/n, t being thickness of glass and n being index of refraction.
If n = were 1.5, f.p. is shifted back (longer) by 2/3 the glass thickness.
The nuisance is determining how far the film plane is offset from the camera back when a film holder is placed in the camera. The glass normally has to be spaced to match a film holder. The yahoo cameramakers group has a document for 2x3 thru I think 8x10 ANSI specs including tolerances for filmholder dimensions. As I understand it there are no consistent standards for film formats larger than 8x10 (or is is 11x14?), so different banquet size ULF cameras differ from brand to brand.
I imagine the people making/selling ULF filmholders have agreed upon some sort of standard (it may be conformity to a given popular camera's glass spacer).
I have been thinking about a glass film holder analogous to enlarger glass negative carriers, for a specific camera design...I can't imagine it costing as much as custom wooden ones, but they would be heavy and awkward.
1) Build camera with ground glass made with anti-reflective glass and spacer determined by step 2 below. Mount with ground side AWAY from lens (opposite of above discussion)
2) Glass film holder consists of a piece of anti-reflective glass at front hinged with regular glass at back. Film is loaded between AR and regular glass panels. AR glass supposedly serves as anti-newton glass (according to some glass-negative carrier page I read. By AR I mean sputtered metallic coated glass (like eyeglass AR coating), not blurry non-glare framing glass. The 2-pane glass-film sandwich would slide into a grove in a light tight simple wooden or aluminum 'holder'. The thickness of the front of the holder assembly and any darkslide would determine the thickness of any spacer required for the in-camera ground glass.
This would be heavy, awkward, maybe a bit impractical, but I think it would work, probably cost less and allow use of unconventional rollfilm like thin-base aerial film that is too floppy to stand up in conventional filmholders.
Seems like most people who use modern ULF cameras can afford the conventional film and filmholders, but I offer this idea for people as strange as me who like to do things the hard way.
