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Hello from Turkey,

I have recently build a new movie theatre has four small auditorium. I would like to know, what is the ideal xenon lambs wattage for my small screens (1600 watt, 2000watt etc). Distances between booth and screen are 1240 cm, 950 cm, 910 cm, 890 cm.
Please, don't say consult your dealer. Because my aim is re-chek my dealer's calculation with your experience.

Regards
Fevzi Genç
Cinema Hayal

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The trow from the projector doesnt have as much to do with lamp wattage as several other factors. Do you have a gain screen? How big is the screen? Do you have good lenses? An efficient lamphouse? I am not a tech but I am sure that these will be the first things they will ask before you get a good answer.

How bright your screens are have very little to do with how far they are from the projection booth. The largest factor is the surface area of the screen and the gain of the screen surface.

A "rule of thumb" for lighting a matte white gain=1 screen is that you need about 5 watts per square foot of anamorphic screen area to achieve 16 footlamberts with a normal 2-blade shutter (50% light efficiency). So a 20 x 48 foot scope image having 960 square feet would need about 5000 watts, and a 25 x 60 foot image having 1500 square feet would need at least 7500 watts to properly light a matte white screen. (Thank you, John Pytlak of Kodak)

I have 10 foot by 24 foot screens in 4 out of five of my houses and use a 2,000 watt xenon lamp. My cinema supplier says I could get away with a 1,600 watt lamp. But the images are good and the lamp life is excellent so I'm not going to switch.

My big screen is 16 feet by 35 feet and is lit with a 3,000 watt lamp. The brightness is acceptable but not great. So I will be looking in to some corrective measures for that screen.

If you are using brand new Kinotone lamphouses then you can go down a lamp size and achieve similar brightness on the screen. If you are using anybody eleses lamphouse, I'd say go with the larger lamp and if you have too much light, defocus the lamp a little.

Lamp, Lens, and Projector manufacturers sometimes offer slide rule calculators that help choose lens focal length and power levels. Power level needed depends mostly on the screen area and the screen gain, as well as the assumed light efficiency of the projection optical system. The 5 watts per square foot of scope image area with a gain=1 matte screen comes pretty close. Properly curved gain screens reduce the power requirement, at the expense of narrower optimum viewing angle.

Both Osram and Strong have good calculators.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: 585-477-5325 Cell: 585-781-4036 Fax: 585-722-7243
E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Website: http://www.kodak.com/go/motion