Hi,
I've modded a 3M 9800 projector to take an OSRAM HQI-T150 MH bulb - dimensions are similar to the original 400W halogen lamp and the MH was able to fit nicely into the existing lamp assembly with a little work - not much difference in brightness between halogen and MH but superior quality of light, longer lifespan + stage remains absolutely cold (which is good for the panel/dismantled screen).
QUESTION: I purchased a NVIEW panel which has a 12" screen aperture. The OHP can accomodate 15" screen size. This means that all the light reaching the OHP stage is not being used. Is it recommended to build something that will direct the light from the lamp to a smaller area (slightly larger than 12") on the stage? It may be seated within the OHP and resemble something like the attached picture. If possible, what will be the preferrable material to construct the thingy and how can I achieve the desired shape?
I've modded a 3M 9800 projector to take an OSRAM HQI-T150 MH bulb - dimensions are similar to the original 400W halogen lamp and the MH was able to fit nicely into the existing lamp assembly with a little work - not much difference in brightness between halogen and MH but superior quality of light, longer lifespan + stage remains absolutely cold (which is good for the panel/dismantled screen).
QUESTION: I purchased a NVIEW panel which has a 12" screen aperture. The OHP can accomodate 15" screen size. This means that all the light reaching the OHP stage is not being used. Is it recommended to build something that will direct the light from the lamp to a smaller area (slightly larger than 12") on the stage? It may be seated within the OHP and resemble something like the attached picture. If possible, what will be the preferrable material to construct the thingy and how can I achieve the desired shape?
Attachments
wow, how can a 400w 36v halogen put out 6000 lumens after going through all the optics? Amazing....
Anyway - im also curious about the light waste. Is there any way to concentrate the light on a smaller area?
Cheers,
Alex
Anyway - im also curious about the light waste. Is there any way to concentrate the light on a smaller area?
Cheers,
Alex
add a precondensor lens right after the bulb to narrow the light path, if you do this you may need to slightly change the location of the fresnel/bulb so they are closer.
I managed to fit the 150W MH in the same position as the 400W halogen. The standard 3M 9800 (and my setup too) has a condenser lens followed by thermal glass, sitting immediately above the bulb. This condenser lens concentrates light on the entire stage area. Are you saying the existing condenser lens needs to be replaced or a further lens(es) needs to be added? I want the light only to reach the stage area where the projection panel is seated, and not beyond. Anyway, if another condenser lens is needed, how do I go looking/specify exactly what I should put in? Also, is it easier just to blackout the unused stage area with, say, insulation tape?
I was unaware you already had a condensor lense in the setup. But I assume you could take it out and find it's focal length, you can get pretty close by looking at it from the top and gettting somthing small as large as you can through the lense, but still clear. Then you could attempt to find a condensor with a similar diameter and shorter focal lenght.
But it might be really hard to find the right condensor, I have a couple condensors with really short focal lenghts that are way to powerful for my 15" lcd, but if they are placed right next to the bulb they might work well for your projection pannel.
But it might be really hard to find the right condensor, I have a couple condensors with really short focal lenghts that are way to powerful for my 15" lcd, but if they are placed right next to the bulb they might work well for your projection pannel.
Thanks for the reply. I'm a bit far away from you (South Africa)! I noticed my OHP has a color tuning knob that controls the position of the optical assembly (bulb+condenser+thermal glass) and has an effect on the brightness/ lighting quality of the stage. Essenrially, I would imagine that this tuning knob fine tunes the focal distance of the condenser so that the light terminates correctly on the fresnel. With the new MH bulb, this knob seems to be at the limit of its adjustment compared to when the halogen was in i.e. with the halogen, I could adjust the stage to go from a partially (90%) & unevenly lit, yellowish to completely & evenly lit, bright white. With the MH, the knob adjustment stops short of bright white, evenly lit stage. Do you think its wise to consider moving the entire optical assembly physically closer to the fresnel stage lens to:
1. light a smaller stage area but evenly?
2. have better control of the condenser focal length?
Sorry for the barrage of questions. Looking forward to your reply!
1. light a smaller stage area but evenly?
2. have better control of the condenser focal length?
Sorry for the barrage of questions. Looking forward to your reply!
I'ld immagine if you made it so the condensor/light assembaly was closer to the fresnel the light would no longer be comming from the fresnels focal lenght, so though their may be more light hitting the fresnel, it will be comming from the wrong angle to pass through it.
What you could also do is look for a rear fresnel with a shorter focal lenght (I don't know if they get any shorter then 220 mm) then you could move the whole assembally closer with better results. But unless the frensnel you bought has the same groove pitch as your front fresnel you would need a new one of those as well.
A more powerful condensor lense would still make a more narrow and concentrated circle of light, which would brighten the lcd as well.
What you could also do is look for a rear fresnel with a shorter focal lenght (I don't know if they get any shorter then 220 mm) then you could move the whole assembally closer with better results. But unless the frensnel you bought has the same groove pitch as your front fresnel you would need a new one of those as well.
A more powerful condensor lense would still make a more narrow and concentrated circle of light, which would brighten the lcd as well.
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