ULF Holder Film Channel Tolerances--Expert Opinions Needed
Background: After years of shooting 4X5 and 8X10 I've been in the process of moving up to 12X20. Recently I bought a restored Korona camera on eBay and, then (from a different seller) three film holders listed as "original Korona," holders that had been converted from glass-plate holders to film, with new darkslides and light traps by AWB. (I thought it would be nice to have holders made by the original manufacturer to insure compatibility with the camera.) The description and pictures were minimal, but the holders were said to be in "good working order."
The problem: After inspecting them, I have several objections to the way these were described, but the main problem for me is the provision for holding the film. Sheet metal was nailed onto the septum and bent, at the edges, into a film loading channel (groove, slot--whatever you want to call it) that is almost 2mm wide--hardly sufficient to keep the film in place or flat. One of them has been updated with new septum material and a film channel of a more typical width, but, in all three, the film is not secured at either end--there's no slot to accept the film at the top, nor the usual hinged light trap that folds over the film at the bottom.
The seller is like a broken record and refuses to discuss it, maintaining that they are in "good working order" and "light tight." For him apparently it is a one-issue matter, but, to my mind, there are other criteria by which filmholders must be judged, namely, can they hold film and hold it flat, without scratching it on the way in? (Additionally, there are protruding nail heads, roughness, and unevenness of the sheet metal.)
I have a couple of questions for any of you who use, or even manufacture, ULF sheef film holders. Is there a given/accepted dimension for the gap in the channel the film loads into, and is it reasonable to claim that such a wide gap in the channel is acceptable? In these it's easy to insert up to nine sheets of film in the inconsistently wide channels. The gap is so wide that it couldn't arrest the natural curve of the film, let alone keep it from sagging or bowing when vertical for exposure. I have to think it would affect sharpness across the whole image, especially at the edges.
To me listing and selling filmholders that are (supposedly) light tight, but can't properly hold the film, is like buying a car, said to be in good working order--with new tires--and then, on taking possession, finding out the engine doesn't run.
After years of using 4X5 and 8X10 filmholders that accomodate the width of one film, am I supposed to accept the kind of slop these holders assure? Or can I call it what it is: a defect that makes the holders unusable--and that should have been disclosed? Sorry for the length of this post, but I'd appreciate your expertise and experience in the matter.