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In my experience, you should keep your lamp burning at no less than 80% of its rated maximum current. You can go over or under by a couple of amps but that's it.

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I would strongly encourage the purchase of such a setup. I'm sure other manufacturers offer the ablity to change bulbs. It will be more expensive to buy a 4000 watt lamp/ power supply, but it will allow some options. If you think the light is too low after you try 3000w, you can go to 4000w. If you ever run 3D, (unlikely, but a 3D film festival is always fun) the additional light will be handy to have. Maybe, 70mm will make a come-back, etc..

There is a price difference between bulbs. I haven't checked recently, but I thought a 3000w bulb costs (something like) $300 (rated for 1200hrs) and a 4000w costs $500 (rated for 800hrs.) Whatever it is, I think there is a big price difference. But, if the screen is dark, you need whatever is required. (What size screen and throw? Is it a matte-white screen, or a gain?)

Wheather you can get away with "overdriving" a 3000w, or reducing a 4000w (to see which is cost-effective in the long run) is hard to say, because I don't know of anyone doing that (hence, no data.) I would feel uncomfortable powering a 3000w bulb over 3000w- ie: I would not go over 100% of it's rated power. On the other hand, (Randy is right) I would not reduce a 4000 bulb to less than 80% (3200w.)

To find apx. wattage required for screen size:
height of screen (squared) times 12 - or:

If your screen is 32ft x 17ft. (I use flat, as it is 'worst-case') that would be:

17 (squared) * 12 = 3468watts
(a 3000w bulb can't be turned up high enough to provided the required light.)

Seeing you are replacing just the old Magnarcs, assuming you are keeping the original pedestals, you would need a standard lamphouse like the Strong Super-80 (3000-7000w capacity, with the corresponding power supply).

As for bulbs: the larger the bulb, the shorter the warranty life, especially if running horizontally. DO NOT run the bulbs at too low a current (below 80-85% of max rating), as all it will do is give you poor performance and shortened lamp life.

As for brands of bulbs: Osram and Christie (Ushio) bulbs are excellent performers in any wattage. *AVOID* the following brands:

ORC/EG&G/PerkinElmer (some of the OEM 'brands' of bulbs (Like the 'CFS' bulbs) were made by ORC)

'Cine-Lite' (and any other Chinese-made bulbs)

Yumex (Though made by former Ushio people, the quality control is pretty spotty)

as always, YMMV...

Aaron

Obviously, a larger lamp will use more electricity. And as noted by others, larger lamps cost more, and have a shorter warrantee. Always choose a lamp that will allow you to meet the SMPTE standard screen luminance of 16 footlamberts throughout its life (light output decreases as a lamp ages).

It's usually easier to deal with an abundance of light, rather than have a lamp that is too small to meet SMPTE standards. You can trade the extra light for improved illumination uniformity, or perhaps even consider a 3-blade shutter to reduce flicker perception. Note that the SMPTE standard allows theatres to be as bright as 22 footlamberts, which IMHO makes most (not all) movies look better. In other words, if you can afford the slightly greater operational cost, err on the side of having a larger lamp than needed.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

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Christie lamps also have an incredible range...eg their CXL-20R has a range of 50-85ADC and is rated for 2400Hours. I have run their lamps anywhere within this range and they last typically 2X-4X their rated hours.

Steve

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