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Author
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Topic: 7k bulb worth it?
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Steve Guttag
We forgot the crackers Gromit!!!
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Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 03-24-2013 02:10 PM
The 6.5KW was "optimized" for the DP2K-32B...I don't believe the 7K was.
A problem arises as one increases lamp size...the arc ceases to behave as a point source so a principle known as Etendue creeps up. The short of is...the smaller the aperture, the smaller the point of light needs to be in order to efficiently get through the aperture.
This is why, with film, 70mm could make use of the larger lamps much better than 35mm. It wasn't just the heat, as many would suspect, you can actually get MORE light from the larger arc on the larger aperture.
The same holds true for digital (the physics has not changed). The smaller apertures can not make as much use of larger lamps because the arcs are getting larger too. The is one of the several reasons why an S2K projector will not be as bright as a .98" projector running the same lamp (and will top out at about 2-2.2KW)...likewise, the 1.2" projectors can make better use of the larger lamps than the .98" ones and so forth.
It is also one of the reasons that lasers are the promise of the larger screens (e.g. Drive-Ins) in the future...one can get a lot of light in a small point. One can also get a narrow bandwidth color without having to split white up with a prism, direct the light to three DLP chips and then recombine the same light you split up (and remember, the wavelengths of the lights are very different so the index of refraction is different for each color...so it is very tricky to do all of this).
I know with film systems, I could get a BRIGHTER picture with a 6KW lamp than with a 7KW lamp using the same manufacturer's lamp on 35mm film.
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