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Author Topic: Lamphouse alignment Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-30-2008 01:31 PM                     After speaking with Strong and searching all related topics, I am out of ideas. We have a Super Highlight II console with a 7K bulb. I have aligned it with the string and with the laser. It all checks out. Working distance is correct (33 1/8"). Left to right brightness is fine. The problem is with up and down. I can't seem to get the light to move down. It is hottest on top. It evenly gets dimmer down the screen. Any ideas?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-30-2008 03:16 PM                     What is the gain of the screen and what sort of downward angle is the machine on you may be seeing the hotspot of the gain of the screen  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-30-2008 03:19 PM                     It is a Silver screen but not sure of the exact gain. It is a 19 degree downward angle. The screen is 70 feet wide. Measurements with the light meter were taken from the booth.  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 10-30-2008 04:01 PM                     When you go in the auditorium does the hot spot stay up top or does it 'follow' you wherever you go. If it follows you, you're not going to get rid of it...it's the silver screen.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-30-2008 04:22 PM                     It doesn't seem to move with me.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-30-2008 04:45 PM                     A silver screen will exhibit a hot spot usually at the top of the screen when viewed from the booth  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 10-30-2008 05:28 PM                       Oh, yes, that's definitely the silver screen doing that... 19 deg. is pretty steep!  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 10-30-2008 05:40 PM                        If it is the screen -- which does seem likely -- it can be partially remedied by tilting the entire screen frame. You can figure out how much of a tilt by standing in center of the theatre and having someone (a crew is more like it with a 70 footer) and pull the bottom of the screen so it is at a downard angle. You should see the hot spot move toward the center of the screen as the pull the bottom further and further back, basically aiming the light toward the center of the auditorium. It is not going to fix the hotspot problem other than centering it more for a good portion of the center sweet seats. If you can get a fairly even placement of hotspot in the center of the theatre, that about the best you can do. There will still be off-axis seat which will still see a hotspot -- it's just the nature of silver. Don't worry where the hotspot is as seen from the booth....no patrons sit up there.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-30-2008 06:10 PM                     Shouldn't I still be able to have some control over moving the light up and down? Measuring from the booth we get 7.3 on top, 5.8 in the middle, and 4.6 on the bottom.  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 10-30-2008 06:15 PM                     Are those measurements are foot lamberts? When you adjust the lamp (or mirror) vertically, does anything happen?  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 10-30-2008 06:17 PM                     Double post [ 11-02-2008, 02:59 AM: Message edited by: John Wilson ]  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-30-2008 06:25 PM                     Yes they are in FL. BTW, we are running 70MM with a heat filter. When I adjust the lamp down, the overall level seems to drop a bit. It moves down slightly but not enough to help anything.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 10-30-2008 06:45 PM                       No. Please. You'll be running around in circles forever trying to balance that out - and it can't be done. Put a black card in front of the porthole and adj the bulb for an even field, then leave it that way. What you get on the screen you are stuck with because it's silvered. Any attempt to compensate will only throw the overall light level down. The screen surface is very directional - therefore, it's not about the rectangle of light you are putting on it, but rather the angle from which the light is falling upon it. What Frank suggested in tilting the screen back would make it look okay from the booth (and if you have an older theatre it may already be tilted back), but then much of the light would also be reflected in that direction. The closer to vertical this silver screen is, the more light will be bounced to the orchestra. Matte white screens, of course, should be tilted for better focus.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-30-2008 06:55 PM                     That would explain a lot Tim. I have been on the phone with Strong all week. I aligned it 3 times with both alignment kits. I also went crazy centering the rear adjustment perfectly, and adjusting the front height of the bulb perfectly to where it not only lined up with the laser but was within Strong's height specs. I went to the extreme of measuring the sides of the bulb to see if all 4 sides were equidistant from the reflector opening. Everything was so centered and aligned and then I hit the screen and was like....oh crap!!! Oh well. I guess that will be the best it's going to be.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 10-30-2008 08:42 PM                        The real answer is to engineer a proper matte white (or close) screen. This will solve your problem. Adjustment of the projection equipment will not solve your problem; it will just confuse the matter. Tim is right. If the silver screen is what you are stuck with, you will never solve this problem; angling the screen will only move the "best" seat around. Louis  |  IP: Logged

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