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Author Topic: Formula Miran Starman Film Handler Posts: 2 From: Medvode, Slovenia Registered: Mar 2002 posted 09-02-2002 04:50 AM                     Did someone could help me with information how to calculate correct wattage for xenon projection lamp according different conditions like: cold - hot mirrors, hot filter, two - three blade shutter, different optics, glass of projection port window, size of screen, gain of screen etc...  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 09-02-2002 06:46 AM                        I don't know if there is a formula which exists to balance those variables, but the bottom line is that you need (according to the SMPTE specs) a big enough lamp to light the screen evenly to 16 foot-lamberts. If, running at maximum current (amps) in the manufacturer's recommended operating range, the screen brightness is less that that, you need a bigger lamp (and possibly a bigger rectifier). If it's significantly over, decrease the current. If you need to decrease the current below the minimum current in the operating range, install a smaller lamp.  |  IP: Logged John Anastasio Master Film Handler Posts: 325 From: Trenton, NJ, USA Registered: Sep 2000 posted 09-02-2002 08:26 AM                        Assuming a shutter efficiency of 50% (two-bladed), I think 5 watts per square foot of screen size should give you a good approximation.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-02-2002 09:43 AM                     There are far too many variables mirror type heat filtering lens efficiency screen gain and aspect ratio I usually take the manufacturers specs and almost double that requirment as there are based on brand new everyitem not 3 years down the road  |  IP: Logged Gerard S. Cohen Jedi Master Film Handler Posts: 975 From: Forest Hills, NY, USA Registered: Sep 2001 posted 09-02-2002 12:22 PM                     Welcome Aboard, Miran! The closest I got to Slovenia was running Meopta projectors. (I liked the micrometer/microscope feature that enabled the precision adjustment of the exciter beam through the sound track.) Good luck, Gerard  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 09-02-2002 08:07 PM                     Question... With the 5watts per square foot guide, will that actually get you to 16fl or take you over into a safety area? Or will it JUST get you there?  |  IP: Logged

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