This is topic Dark corners in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Brian Paymer (Member # 57) on 07-02-1999, 09:27 PM:
I've got an auditorium where no matter how much I de focus the bulb I can't get rid of the dark corners in scope mode. It doesn't show up in flat mode. Any tips here would be appreciated.
Posted by Brad Miller (Member # 2) on 07-02-1999, 11:22 PM:
I am assuming this is a short throw/large screen setup? I'll bet if you unscrew the backup lens from the anamorphic and remove any dummy rings (so the two lenses will be closer together) that will solve your problem. Many flat/backup lenses come with a huge (about an inch long) ring to mount as a flat lens and many engineers do not remove this when mounting to an anamorphic.
Assuming this is your problem, the image is actually hitting the inside barrel of the lens causing your dark corners.
Posted by Aaron Sisemore (Member # 145) on 07-03-1999, 01:24 AM:
Another cause is the distance between the projector head and the lamphouse, if you have a way of sliding the lamphouse or the lamp unit inside the console) you should be able to fix the vignetting (the technical term for the dark corner problem) rather easily. Aaron
Posted by Brian Paymer (Member # 57) on 07-03-1999, 11:53 PM:
It worked! Thank you guys. I would never have guessed it to be something as simple as an extra lens ring.