Time between winds and film path radius are probably the biggest factor for producing a bulge of the film in the film gate. I suspect different bases and the presence of a paper backing contribute more to the between-film variability than the thickness of the emulsion. One of the main reasons I'll pick up the 4x5 camera instead of a MF rollfilm camera is that the 4x5 film usually holds very flat (hasn't bulged on me yet). Whereas with rollfilm this bulging is my nemesis

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Check out page 3:
http://www.zeiss.de/C12567A8003B8B6F/EmbedTitelIntern/CLN10e/$File/cln10e.pdf
i'm curious what camera or system you have have film bulging problems with, I cant say i have had with any (hasselblad for decades, vintage folders, bronica, rb67 etc etc) unless there was something wrong somewhere along the line with the camera or loading film etc. i use large format as well and like for its own added attributes it provides, i also shoot some vintage [camera] formats like 9x12, as an example they need metal film sheaths to take film instead of the dry glass plate they were designed for, before you even begin with these the film is .3mm to .5mm away from where it is supposed to be because of the added film sheath thickness, but this small margin makes no noticeable impact on the end picture (its small error diminished with DOF even wide open and close focus etc).
i guess where i am going with this is, while that article is interesting i think it has to taken with in its context, reasons behind it and also noted that it is
just an article, no proof was given (results hadnt been done), only speculation really and no follow on have i seen from that article nearly ten years ago (less of a need to now perhaps because sensors are obviously flat and not an unknown quantity once inside the camera as film is, or the results really didn't matter or show any noticeable effect!) . in addition there are other reasons given for unsharp pictures such as camera shake (no doubt one of, if not the major contributor to unsharp pictures (on a day to day real life basis) and so on.
they are talking about a testing machine to measure film curvature down to the millionth's of a mm, no doubt zeiss would find this information useful in the lens design and production business because they would want to understand how much unsharpness is attributed to their lens and how much can be shifted to the film as a cause of unsharpness, something that they would of had difficulty measuring before. it should also be noted that they are testing the film using
very fast modern multi element medium format lenses (wide through to tele f4/350 etc) and the article makes the point that at these extreme wide open limits, is where these sorts of unsharp errors may show up.
this sort of high performance is not really a factor with 120 roll film folding cameras, the lenses are no faster than f2.8 at 75mm -80mm and about f3.5/105mm for a 6x9 folder, DOF should easily cover up any minute problems with film curvature.
still, it was an interesting article, the time theory is interesting but if they are going to be scientific about it then other factors such as temperature etc would all factor into it as well i would think, it
may also not be as relavent to a vintage folder compared to a compact modern roll film back considering the folding camera in some cases will be a longer base dimension/not as sharp bends in film. just a thought
i am not saying it is the ideal format, it is what is it is...its not bad though considering its stood the real test of time ..years of production
