Im just wondering what is the minimum bulb (lumins)power that i can use for a projector with a ps1 lcd inside. Would 1000 lumins be enough in a dark room? And how much light % does an lcd take away?
many thanks Rob
many thanks Rob
lcd take 95% of the light and in addition the ligh distribution is omnidirectional while your screen represent only a small part of the total 3-5%.
in contrast as your lcd is small if you find a projection lens of the size of your lcd you will suppres the field fresnel and loose less light than other.
i'll recommand 10000lumens as a minimum if you do not work on the reflector/condensor part.
if you use good condensor and reflector maybe a 70w mh settings would be ok for an extreme minimum. but we always want better lumens output after some time using the pj
in contrast as your lcd is small if you find a projection lens of the size of your lcd you will suppres the field fresnel and loose less light than other.
i'll recommand 10000lumens as a minimum if you do not work on the reflector/condensor part.
if you use good condensor and reflector maybe a 70w mh settings would be ok for an extreme minimum. but we always want better lumens output after some time using the pj
lumens vrs lux
Lumens is Lux ("brightness") over a 1 square meter area. (For example, if you had a 1 square meter image and every point on the image measured 100 Lux, then the projector would have an output of 100 Lumens.)
Say you can make a 50" diagonal image with 100 Lux at the center, with a particular projector. If you move the projector back to around twice the throw distance, you would get a 100" diagonal image. But the same amount of light (Lumens) would then be spread over a screen area 4 times larger, so it would have 25 Lux at the center.
Both of those images would have the same number of Lumens, but Lumens do not make a watchable image! You need about 100 Lux at each point on the screen, or it is too dim to be pleasant.
So the answer is: You asked the wrong question. For any number of Lumens coming out of a projector, you can make a small enough image to get 100 Lux. But if the size of that image is smaller than the LCD, then you would be better off just looking right at the LCD!
Lumens is Lux ("brightness") over a 1 square meter area. (For example, if you had a 1 square meter image and every point on the image measured 100 Lux, then the projector would have an output of 100 Lumens.)
Say you can make a 50" diagonal image with 100 Lux at the center, with a particular projector. If you move the projector back to around twice the throw distance, you would get a 100" diagonal image. But the same amount of light (Lumens) would then be spread over a screen area 4 times larger, so it would have 25 Lux at the center.
Both of those images would have the same number of Lumens, but Lumens do not make a watchable image! You need about 100 Lux at each point on the screen, or it is too dim to be pleasant.
So the answer is: You asked the wrong question. For any number of Lumens coming out of a projector, you can make a small enough image to get 100 Lux. But if the size of that image is smaller than the LCD, then you would be better off just looking right at the LCD!
I think the first two responses are faily poor.
10,000 lumens is not the minimum by any stretch of the imagination.
I have a 250watt ohp - the cheapest and least bright that you can buy. From memory this kind of OHP puts out 2,000 Lumens and yes, in a lit room it is useless, however, in a dark room it is really quite good and gives an imagine on a 2 metre by 1.5 metre screen (with a throw distance of about 3 metres and an lcd of 10 inches) that has impressed everyone who has seen it.
With my set up we aren't talking professional standards - but if you are looking for a big screen experience on a small budget then it is just fine.
I think too many people on this board have gone crazy on DIY - it was suppposed to be cheap and get good results - although I haven't been reading the board for several months, it seemed to me when I last looked that people where spending so much on components that they could have bought a brand new commercial projector.
Good luck with your project.
10,000 lumens is not the minimum by any stretch of the imagination.
I have a 250watt ohp - the cheapest and least bright that you can buy. From memory this kind of OHP puts out 2,000 Lumens and yes, in a lit room it is useless, however, in a dark room it is really quite good and gives an imagine on a 2 metre by 1.5 metre screen (with a throw distance of about 3 metres and an lcd of 10 inches) that has impressed everyone who has seen it.
With my set up we aren't talking professional standards - but if you are looking for a big screen experience on a small budget then it is just fine.
I think too many people on this board have gone crazy on DIY - it was suppposed to be cheap and get good results - although I haven't been reading the board for several months, it seemed to me when I last looked that people where spending so much on components that they could have bought a brand new commercial projector.
Good luck with your project.
my answer was based on the bulb we use the more often: metal halide which are also not ponctual and induce some choice.
having a smaller bulb will might give you more efficiency thus lees need for lumens.In contrast with a mh bulb we use only between 5-30% of the lumen initial output.
now if you like to take some ohp bulb with a 450h life time this is ok too. just check your budget.
having a smaller bulb will might give you more efficiency thus lees need for lumens.In contrast with a mh bulb we use only between 5-30% of the lumen initial output.
now if you like to take some ohp bulb with a 450h life time this is ok too. just check your budget.
comparible light sources
Yes, let's compare standard OHP lamps to MH lamps:
If your 250 Watt OHP lamp costs $5 and runs for 500 hours to give you 2000 lumens, then that is 1 cent per hour plus 1/4 Kwatt of electricity,say about 2 cents per hour. Total = 3 cents per hour. (These numbers for OHP lamps are VERY optimistic.)
In other recent threads here we have been discussing Ushio MH retrofit lamps for $38, and ballasts for $28, but let's just say you went with a 250 Watt MH lamp & ballast combination that cost you $100. Since the lamp runs for 15000 hours, that would work out to 0.67 cents per hour plus the same 2 cents per hour of electricity. Total = 2.67 cents per hour.
BUT: The Ushio 250 Watt retrofit MH lamp puts out 20000 lumens, so your image would be 10 times brighter for less per hour of operation. The MH lamp will also give you a much better color temperature, so the whites will be whiter and the colors truer. Maybe even more important, the MH lamp is much more efficient which means most of the 250 Watts becomes light. In a tungsten halogen OHP lamp, most of that 250 Watts becomes heat, so you have to do a lot more cooling.
There is certainly a niche for low-cost DIY projection, but it would work better with a 70 Watt or 150 Watt MH lamp (both brighter than a 250 Watt tungsten halogen lamp).
Yes, let's compare standard OHP lamps to MH lamps:
If your 250 Watt OHP lamp costs $5 and runs for 500 hours to give you 2000 lumens, then that is 1 cent per hour plus 1/4 Kwatt of electricity,say about 2 cents per hour. Total = 3 cents per hour. (These numbers for OHP lamps are VERY optimistic.)
In other recent threads here we have been discussing Ushio MH retrofit lamps for $38, and ballasts for $28, but let's just say you went with a 250 Watt MH lamp & ballast combination that cost you $100. Since the lamp runs for 15000 hours, that would work out to 0.67 cents per hour plus the same 2 cents per hour of electricity. Total = 2.67 cents per hour.
BUT: The Ushio 250 Watt retrofit MH lamp puts out 20000 lumens, so your image would be 10 times brighter for less per hour of operation. The MH lamp will also give you a much better color temperature, so the whites will be whiter and the colors truer. Maybe even more important, the MH lamp is much more efficient which means most of the 250 Watts becomes light. In a tungsten halogen OHP lamp, most of that 250 Watts becomes heat, so you have to do a lot more cooling.
There is certainly a niche for low-cost DIY projection, but it would work better with a 70 Watt or 150 Watt MH lamp (both brighter than a 250 Watt tungsten halogen lamp).
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