Film-Tech Forum ARCHIVE: Odd blemish during show

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Posted by Carmine Occhino (Member # 1699) on 06-06-2003, 12:20 AM:

During projection, there is an odd glare on the screen. It does not look like a hot spot or from an improperly focused bulb. I could best describe it as two fine streaks very close together in the middle of the screen. Nobody has ever complained about it except my brother [Mad]

. I see it in both screens at my theatre. Cleaned all optics and I still see it. I guess it has to be a slight problem with the lens ?

Posted by Mike Pennell (Member # 1692) on 06-06-2003, 12:35 AM:

Do you have light escaping from the lamphouse? Shut the hand dowser and lower the house lights and see if they are still there. [beer]

Posted by Darryl Spicer (Member # 711) on 06-06-2003, 12:45 AM:

you see it on both screens? Sounds like there may be something behind both screens causing a reflection of light.

Posted by Mike Blakesley (Member # 26) on 06-06-2003, 02:06 AM:

Could it be a reflection from some framework holding up the center speaker? Is it visible from all locations in the auditorium?

Posted by Jim Spohn (Member # 1547) on 06-06-2003, 10:05 AM:

I've seen light leaks from EXIT lights....Jim

Posted by Greg Mueller (Member # 17) on 06-06-2003, 10:11 AM:

Straight streaks, or curved ones?

Posted by John Anastasio (Member # 607) on 06-07-2003, 06:33 AM:

I had a straight streak that turned out to be a stray beam from the lamphouse reflecting through an open door and off the shiny surface of a framed movie poster [eyes]

Posted by Carmine Occhino (Member # 1699) on 06-08-2003, 02:26 AM:

Mike P., after doing what you said as far as I can tell there is no light escaping from the lamphouse. I looked around behind the screen and in the theatre and I don't see a cause there. Greg, its two straight steaks. It only is really visible during light scenes, and even then it is not a major problem but I don't like not knowing the cause of problems. The way it looks though my gut says its coming from the lamphouse. These cinemeccanica's have the air tube cooling the anode, could this cause a disturbance in the light ?

Ps-John A.,that's some run away beam.

Posted by Phillip Seib (Member # 1406) on 06-08-2003, 03:16 AM:

Carmine,
Hows the screen. Is it streaked from soda or other liquids.

Posted by Daryl C. W. O'Shea (Member # 1303) on 06-08-2003, 03:23 AM:

Speaking of the screen, by close together do you mean the streaks are about 6-8 feet apart and (nearly) top to bottom? Is it the seams in the screen showing up?

Posted by Carmine Occhino (Member # 1699) on 06-08-2003, 04:48 AM:

I don't see any stains on the screen from liquids. The streaks are almost right next to each other, no more than a few inches apart and they cover a bit more than three quarters of the screen top to bottom. O'Shea there are no seams , if by seams you mean ends joined together, to show up.

Posted by Mike Pennell (Member # 1692) on 06-08-2003, 05:11 AM:

Do the streaks appear with no film threaded and only white light? How about with the lens pulled? Or does it only happen with the flat or just the scope? How about the portglass? Is there any weird reflections coming off the frame? I'm stumped [Confused]

Posted by Thomas Procyk (Member # 1170) on 06-08-2003, 08:56 AM:

For a long time on one of our screens at a theater I used to work at had a strange L-shape of light on it. After looking at all the projection-related causes, we found it was one of the side walkway lights shining up on the metal hand rail of the stadium section, and bouncing up onto the screen! [Eek!]

If it's only in the really light scenes, it sounds like something is being reflected back FROM the screen rather than stray light hitting your image. If you can't see the streaks when you move around the auditorium, then it HAS to be something behind there, even if it doesn't look obvious. It could even be a row of those little nail things with the discs around them that hold up the insulation-type stuff to the back wall?

=TMP=

Posted by Carmine Occhino (Member # 1699) on 06-09-2003, 12:40 AM:

Thanks for all the replies guys...I discovered the problem. I ran light on the screen and marked the spot where the streak is. Then I got as close to the screen as possible and ran my finger across the spot. Turns out there is a seam there, which I could'nt see, and the streaks are appearing on both sides of the seam. Again, it is not very noticeable and I wouldn't bother with it but I'm curious if there is a fix for that such as tightening the screen. Thanks Daryl C.