Ok well i could start with frensels but im not going to cos its going to cause a stir lol but i have found out quite a few things and im so suprised manny of u havnt realised of a ohp frensels properties to a page mag's properties, in simpler words a page mag will give u a more intense brighter light, a ohp frensel more dull an diffused light, why? cos a ohp frensel has more rings that not only diffuse light but also bend rays to stray angles and the thickness absorbs alot of light! a page mag is brighter cos its thin thus not absorbing much light, it has fewer rings so there is less light getting wased gettting bent at right angles out of the side and the light is more intense hence the lesser rings. Now as i said im not going to into this but a page mag is not good for a ohp, why u may ask? just have a look at the angle the light has to bend in a ohp from the source it is too much for the lesser rings that need to capture and rebend the light at a straiter angle, u can try the page mag if u want but your corners will be dimer than a ohp frensel.
Ok for those who are going to post ahhh the page mags are crap cos of the lesser rings and the rings on the screen, hm not so, u need to have it atleast 1" away from the screen i find 2" is best that way making the page mag out of focus to the projection lens and u will have just the lcd infocus.
for an experiment take a varible beam torch and vary the beam from wide to narrow, what happends is when the light is wider its less bright , intense and less concentrated and that is what its like in a ohp from a point source, now if u use a larger burning arc the beam is at a lesser angle and therfore it is more concentrated and intense, that is why small lcds get a brighter image than a larger lcd, if u could scale up the light source size in a smaller lcd setup u would get the same resaults with a bigger screen ie: a 15inch lcd, bear in mind u will need a larger condenser and a larger reflector but its not that much bigger, another thing is the size of the projection lens the smaller the dimmer, the bigger the more light passes through!
Ive been fooling around on this subject a while now in the way why a 49000lm bulb in a ohp is so dim on the wall, the secret lies in your reflectors, light angles, and frensel
Trev
Ok for those who are going to post ahhh the page mags are crap cos of the lesser rings and the rings on the screen, hm not so, u need to have it atleast 1" away from the screen i find 2" is best that way making the page mag out of focus to the projection lens and u will have just the lcd infocus.
for an experiment take a varible beam torch and vary the beam from wide to narrow, what happends is when the light is wider its less bright , intense and less concentrated and that is what its like in a ohp from a point source, now if u use a larger burning arc the beam is at a lesser angle and therfore it is more concentrated and intense, that is why small lcds get a brighter image than a larger lcd, if u could scale up the light source size in a smaller lcd setup u would get the same resaults with a bigger screen ie: a 15inch lcd, bear in mind u will need a larger condenser and a larger reflector but its not that much bigger, another thing is the size of the projection lens the smaller the dimmer, the bigger the more light passes through!
Ive been fooling around on this subject a while now in the way why a 49000lm bulb in a ohp is so dim on the wall, the secret lies in your reflectors, light angles, and frensel
Trev
if anyone has an idea to modify a ohp for a brighter light output with the same source light fell free to ad, all ideas are welcome, lets make those ohp's realy pump out those lumens we ought to be getting
Trev
Trev
I hope I'm not going off-topic too much here...
I've bought a 2nd hand Toshiba tlp-670 (xga,1300 ansi, 20 euro hehe) and compared the result with my ohp setup. The damn thing is so bright that it hurts my eyes. And it only uses a 150W bulb!
Ok, it has a prism to split the incomming light into RGB so every lcd only gets the color it needs but that only accounts for a factor of 3 in brightness. And I think the toshiba is more than 3 times as bright as my ohp setup.
(off-topic: the contrast of the toshiba is 300:1 ansi & 400:1 full on/off but my ohp setup visibly beats it).
Anyway, the toshiba uses a cube shaped prism to collect the light from the 3 lcd's and it bundles the light from those 3 sources and directs it towards the lens. Isn't it possible to use such a prism for multi-source lights (halogen/MH or whatever)???
I've bought a 2nd hand Toshiba tlp-670 (xga,1300 ansi, 20 euro hehe) and compared the result with my ohp setup. The damn thing is so bright that it hurts my eyes. And it only uses a 150W bulb!
Ok, it has a prism to split the incomming light into RGB so every lcd only gets the color it needs but that only accounts for a factor of 3 in brightness. And I think the toshiba is more than 3 times as bright as my ohp setup.
(off-topic: the contrast of the toshiba is 300:1 ansi & 400:1 full on/off but my ohp setup visibly beats it).
Anyway, the toshiba uses a cube shaped prism to collect the light from the 3 lcd's and it bundles the light from those 3 sources and directs it towards the lens. Isn't it possible to use such a prism for multi-source lights (halogen/MH or whatever)???
heya rapsac not off topic at all, this thread is about light and i welcome all ideas on the subject, ok firstly u wana sell that projector of yours? lol
secondly the prisim would work for a multi light gathering source but u would need a big prisim say for 3x 250mh and the prisims cost abit to buy, its a good idea
now why is your projector brighter, the toshiba im talking about, ok a couple of reasons there, 1 u have the 3 lcds that have the light x3 so say 30% of the source, and secondly in these pro projectors they have double condensers, meaning in a standard ohp they use 1, why? to make the beam wider, now if u use 2 condensers face to face the beam stays narrow so it doesnt get any wider making the beam concentrated and very bright, that is a main reason why the small lcd projectors of now days are so bright.
trev
secondly the prisim would work for a multi light gathering source but u would need a big prisim say for 3x 250mh and the prisims cost abit to buy, its a good idea
now why is your projector brighter, the toshiba im talking about, ok a couple of reasons there, 1 u have the 3 lcds that have the light x3 so say 30% of the source, and secondly in these pro projectors they have double condensers, meaning in a standard ohp they use 1, why? to make the beam wider, now if u use 2 condensers face to face the beam stays narrow so it doesnt get any wider making the beam concentrated and very bright, that is a main reason why the small lcd projectors of now days are so bright.
trev
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