If it's anything like the situation with The Long Goodbye, it may well be down to some less than perfectly-calibrated optical printing - the giveaway is if there's a dissolve or similar optical transition in the same shot.jindianajonz wrote:I always thought explanations like this were interesting; is there anywhere that you know of that goes into detail on the causes of different types of film damage? I always wondered about the unmoving lines that occasionally occur- how did the same damage end up in the same location on multiple frames?MichaelB wrote:I don't know for certain, but my educated guess is that it's a by-product of creating the dissolve between the two shots during the film's original post-production - a small bit of dirt ended up in the optical printer, and because they were working from the negative at the time it's registered as a white dot.
And of course you often see fixed damage on shots featuring titles or other onscreen text, for the same reason.
But vertical scratches, or tramlines, are caused by the print being physically scratched at some point, often due to something as annoyingly simple as a piece of grit in the projector gate. They're very very hard to remove, for the same reason that the Long Goodbye restorers decided to leave well alone, although the effect can be minimised by "wet-gating" the print (bathing it in fluid) during telecine. But that only works if the scratches physically affect the actual print being telecined/scanned - if they've been printed in from another source (for instance, if the print you're working with is a dupe of a different damaged print), wet-gating doesn't work.