Originally Posted by
Doremus Scudder
Alan,
If you take some time next time when loading your holder, you can see that you can move the film around a bit along the short axix with your fingertip; the fit can't be too tight or you wouldn't be able to load the holder. After closing the flap, the same is true along the long axis. Take a loaded holder and shake it around next to your ear. You'll be able to hear the film moving around.
So, it's always a good idea to tap the bottom of your holder (whichever side that is, long or short) against the palm of your hand just before inserting it in the camera to "seat" the film so it doesn't shift during exposure.
If you don't, and use longer exposure times, the film can slip down during exposure resulting is an overlapping double image. (Don't ask me how I know...)
And, if you point the camera down significantly (think photographing a floor), the film can bow out present a curved surface to the lens.
Astrophotographers, who use really, really long exposures often ensure against film movement by using adhesives or a vacuum holder. As the film format gets larger, these problems become worse, but don't think 4x5 film is immune.
However, if you tap your holders and take reasonable care, then you shouldn't have problems.
Best,
Doremus
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