I think I'm the forum member Bob's referring to. I am planning to see if the bulb retrofit will work with an overhead projector/lcd panel combination.
I may be able to test it this weekend, but perhaps not until next week since I don't have all the parts yet.
The bulb costs $89, ballast $112, and connector/socket $14. The bulb does put out around 12,000 lumens, and I'm hoping that will yield an overhead that puts out at least 4000 lumens, which might translate to a picture with LCD panel (which sucks lumens away) of 300 or 400 lumens. That would make me very happy, since the bulb has a rated life of 8,000 hours and the ballast can be used with another bulb.
It's true that the spectral distribution of the bulb has some spikes. But it's a fairly new technology HQI metal halide bulb that has a mostly smooth color spectrum with a much higher CRI than general purpose metal halides. Has a CRI (color rating index) of around 90 out of a theoretically perfect 100 as opposed to the 60 rating that is common for general purpose metal halides.
Also, the rated color temperature of the bulb I'm getting is 10,000K. I know, sounds really high. There are some available that have temp ratings of 6,500k but the people who are using those to light reef aquariums (a surprisingly big market for this kind of bulb) report that the 6500K bulbs are slightly yellow in comparison to the 10,000K and that the 10000K bulbs don't appear bluish. In any case, the screen I'll be projecting these things on has a slightly yellow tint so I'm figuring that will lower the white point a bit. And lots of projectors being used for HT have actual color temp ratings of well above 10,000K (even if manufacturer disagrees); just go to P. Putnam's site and look at his color temp measurements.
My planned application is not for home theater. I'm constructing a multiple projector simulator box for a computer driving sim. I want a picture that's as bright as possible while still being cheap. The three retrofitted projectors, if they work, will hopefully throw off an image of around 400 lumens of non-yellowish (important) light, and they will have bulbs with a rated life of 8,000 hours that can be replaced for $90.
Getting a cost effective solution is more important to me than getting something that's well-suited for HT. But I'm still hoping that it will be pretty decent. The total cost for the overhead projector/lcd panel/retrofit metal halide combo will be around $400-$600 per projecting unit. That's with only a 640x480 resolution, which is fine for my purposes. It might be possible to find a bargain basement LCD projector for that price, but not one that has bulbs replaceable for a reasonable cost.
Having said all that, I still have no idea whether my retrofit project will pan out. But I'll find out within a week or so. If not, I'll be unloading some stuff on eBay (which is where everything other than the bulbs came from anyway). -- Herb
[This message has been edited by hsitz (edited 04-18-2001).]