I believe that's a cue dot, although most of the one's I've seen are oval in shape. I'm far from a film expert, but I did find this: http://www.weavervale.co.uk/onscreen/project1.htmdokidoki wrote:...Awful colours, rainbows, and a big black spot that's there for five frames!...
The region 1 DVD of Mononoke is a mess in some sections, too. I have the R2 of it, but haven't had a chance to watch it yet. And I think Kusoyaro's "Self Titled" had some trouble with Mononoke, something about the aspect ratio being off....You may have noticed in the cinema and on TV that every so often a black spot - known as a cue dot appears in the top left hand corner of the film. These tabs were used to accurately run dual projectors.
Projectors would be set up so that the film was always laced up with 9 diamond - i.e. the diamond shape that appears after the number nine on the leader, directly in front of the lens. As soon as the first cue dot appears - for four fames, the projectionist starts up the second projector, and on the second cue dot right at the very end of the reel, the projectionist opens the shutter to let the light through the second projector and switches the sound over by pressing a button on the front of the projector...
Anyway, I've only used R2 footage twice and in both cases - Totoro and Windaria - the quality has been excellent.
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