Hi!
Originally posted this message as an answer for ds21's message in another thread. The subject is somewhat of topic on that other thread and people seem to missed this one. I'd like to hear people's comments about my views on this matter. So here we go:
quote:
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Originally posted by ds21
Also, 1000 Lumens doesn't seem like much, although I'm not sure of how much Lumens our LCD panels are eating up.
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I might wonder a bit of topic with this "speach" of mine, but I feel that this is seems to be a good place for stuff on subject why does it seem so small to our EARS and some (possibly very close to the truth) guesses about how much lumens the panels actually eat:
Most LCD's that are used on "put a LCD on top of OHP" -setups eat easily up to 80-95% of lumens that the OHP is able to produce (as is quite easily seen on reports of DIY people on this site). This is probably the biggest reason for these MH-retrofits (replacing the usual 250-600w (10000-20000 lumens) halogen with 400w-600w (20000-40000 lumens) MH-lamps). With a 250w halogen a normal OHP produces output of about 2000 lumens. Throw in a LCD that is not even meant for projecting and you'll end up with about 100-200 lumens or even less as can be seen on many threads on this site as people complain about the about non-existend brightness on many projects.
This dramatic drain of lumens at the point of the LCD-panel is probably the biggest reason for the twisted impression that 1000 lumens output is dim or at least not enough. We've become used to numbers like even 40000 lumens that some MH bulbs throw out and so on when we browse trough internet and read trough these forums.
With those LCD's that are meant for projecting the results usually are better and when someone posts about their results then there is a thread that has tons of people wondering about "how the heck is that possible with 250w halogen?" Therefor I'd assume that these panels are a bit different compared to the panels of LCD-monitors and such, and able to project more light trough them to the screen, maybe with a 60-85% drain. There might be some films in front and behind the actual panels to help more light trough and such things. At least it seems to be so by reading some messages about people's results on this forum.
I might add one more thing to this subject about how much light does LCD panels pass trough them. My own old 500 lumen Sony projector is now retrofitted to take cheap halogens and I get a viewable image even with 150w halogen (I'd say maybe about 200-300 lumens, about half of the 500 lumens it gave with the 120W UHP lamp). The old 150w halogen gave out about 4000-5000 lumens (it was really old) and the optics take in my case at least 30-50% (reflector can't reflect everything and there is of course lots of light that goes absolutely somewhere else than it is supposed to go as you can see @http://robo.zapto.org/semidiy there is lots of areas around the lamp where there is nothing that guides/reflects light towards the direction where it should be going), so even a professional product with highly optimized optics and so on seems to be able to let only about 10% trough of the light that is provided after lightsource's optics!
1000 lumens output is very VERY good. It is well viewable in daylight without curtains in a normal living room (well, with that exception that if the sun shines directly in to the room then you will not be able to project very well, not with any kind of projector I'd say). Even 500 lumens output is really really ok, the brightness is ok even with curtains open on a somewhat cloudy day. These numbers are based on my own real experience with commercial LCD- and DLP-projectors that I have used at home and at presentations in my work.
So.... I think I've said quite a lot about this stuff (again)... I'll just repeat my main point again ....1000 lumens.... I'd say that it is pretty ok brightness!
Regards
HB
Originally posted this message as an answer for ds21's message in another thread. The subject is somewhat of topic on that other thread and people seem to missed this one. I'd like to hear people's comments about my views on this matter. So here we go:
quote:
--------------------------------------------------------------------------------
Originally posted by ds21
Also, 1000 Lumens doesn't seem like much, although I'm not sure of how much Lumens our LCD panels are eating up.
--------------------------------------------------------------------------------
I might wonder a bit of topic with this "speach" of mine, but I feel that this is seems to be a good place for stuff on subject why does it seem so small to our EARS and some (possibly very close to the truth) guesses about how much lumens the panels actually eat:
Most LCD's that are used on "put a LCD on top of OHP" -setups eat easily up to 80-95% of lumens that the OHP is able to produce (as is quite easily seen on reports of DIY people on this site). This is probably the biggest reason for these MH-retrofits (replacing the usual 250-600w (10000-20000 lumens) halogen with 400w-600w (20000-40000 lumens) MH-lamps). With a 250w halogen a normal OHP produces output of about 2000 lumens. Throw in a LCD that is not even meant for projecting and you'll end up with about 100-200 lumens or even less as can be seen on many threads on this site as people complain about the about non-existend brightness on many projects.
This dramatic drain of lumens at the point of the LCD-panel is probably the biggest reason for the twisted impression that 1000 lumens output is dim or at least not enough. We've become used to numbers like even 40000 lumens that some MH bulbs throw out and so on when we browse trough internet and read trough these forums.
With those LCD's that are meant for projecting the results usually are better and when someone posts about their results then there is a thread that has tons of people wondering about "how the heck is that possible with 250w halogen?" Therefor I'd assume that these panels are a bit different compared to the panels of LCD-monitors and such, and able to project more light trough them to the screen, maybe with a 60-85% drain. There might be some films in front and behind the actual panels to help more light trough and such things. At least it seems to be so by reading some messages about people's results on this forum.
I might add one more thing to this subject about how much light does LCD panels pass trough them. My own old 500 lumen Sony projector is now retrofitted to take cheap halogens and I get a viewable image even with 150w halogen (I'd say maybe about 200-300 lumens, about half of the 500 lumens it gave with the 120W UHP lamp). The old 150w halogen gave out about 4000-5000 lumens (it was really old) and the optics take in my case at least 30-50% (reflector can't reflect everything and there is of course lots of light that goes absolutely somewhere else than it is supposed to go as you can see @http://robo.zapto.org/semidiy there is lots of areas around the lamp where there is nothing that guides/reflects light towards the direction where it should be going), so even a professional product with highly optimized optics and so on seems to be able to let only about 10% trough of the light that is provided after lightsource's optics!
1000 lumens output is very VERY good. It is well viewable in daylight without curtains in a normal living room (well, with that exception that if the sun shines directly in to the room then you will not be able to project very well, not with any kind of projector I'd say). Even 500 lumens output is really really ok, the brightness is ok even with curtains open on a somewhat cloudy day. These numbers are based on my own real experience with commercial LCD- and DLP-projectors that I have used at home and at presentations in my work.
So.... I think I've said quite a lot about this stuff (again)... I'll just repeat my main point again ....1000 lumens.... I'd say that it is pretty ok brightness!
Regards
HB
Loss of lumens at the beginning
Here is a good example (attached file) what I am talking about the loss of lumens with the optics of the light source. I am not sure that how much the case is similar with OHP's and such, but this is how the stuff was done with the diaprojector where I ripped the stuff for my semidiy-LCD-projector. As you can see it is not hard to prove the loss of 35% of the 5000 lumens that the 150w halogen has to offer in this setup. I also got new information (thanks Joseph!) about the very same lamp that was on this LCD-projector of mine originally. It's output is "ridiculous", only 7000 lumens! Here is link to the original lamp's specs http://www.lamptech.co.uk/Spec Sheets/Philips UHP120.htm and image of the actual bulb. As you can see it has a very efficient reflector on it (all around the point where the light is produced) and so I'd assume that easily 85-95% of the 7000 lumens were collected for the projector to use. The original lamp which was on this Sony is physically the same (maybe the reflector's shape is a small bit different, some small optimization to fit absolutely perfectly with the optics of the projector) but the average life was 2000hrs, not 6000hrs like the one on the website. I'll assume that the lamp was driven with maybe a bit stronger voltage to get a bit more brightness (maybe 8000-9000 lumens) and maybe cooled a little less then it is supposed for the 6000hrs life.
So... I'd advice about anyone that reads this to check the reflector and such stuff right next to the lamp. I am personally going to try to get a new reflector to my system to collect more light, altough it might be unnecessary as the loss is "only" 35% so getting a 250w halogen with 10000 lumens should be enough to get the 500 lumens out of the projector in the end. The cooling with a more efficient reflector would be definetly harder and so the lamp life would possibly be shorter.
Regards
HB
Here is a good example (attached file) what I am talking about the loss of lumens with the optics of the light source. I am not sure that how much the case is similar with OHP's and such, but this is how the stuff was done with the diaprojector where I ripped the stuff for my semidiy-LCD-projector. As you can see it is not hard to prove the loss of 35% of the 5000 lumens that the 150w halogen has to offer in this setup. I also got new information (thanks Joseph!) about the very same lamp that was on this LCD-projector of mine originally. It's output is "ridiculous", only 7000 lumens! Here is link to the original lamp's specs http://www.lamptech.co.uk/Spec Sheets/Philips UHP120.htm and image of the actual bulb. As you can see it has a very efficient reflector on it (all around the point where the light is produced) and so I'd assume that easily 85-95% of the 7000 lumens were collected for the projector to use. The original lamp which was on this Sony is physically the same (maybe the reflector's shape is a small bit different, some small optimization to fit absolutely perfectly with the optics of the projector) but the average life was 2000hrs, not 6000hrs like the one on the website. I'll assume that the lamp was driven with maybe a bit stronger voltage to get a bit more brightness (maybe 8000-9000 lumens) and maybe cooled a little less then it is supposed for the 6000hrs life.
So... I'd advice about anyone that reads this to check the reflector and such stuff right next to the lamp. I am personally going to try to get a new reflector to my system to collect more light, altough it might be unnecessary as the loss is "only" 35% so getting a 250w halogen with 10000 lumens should be enough to get the 500 lumens out of the projector in the end. The cooling with a more efficient reflector would be definetly harder and so the lamp life would possibly be shorter.
Regards
HB
Attachments
Overhead calcs.
Another thing to consider. The luminous output spec'd for an overhead is the total output across the entire stage area. The projection panels only take up a small percentage of this area.
Example: Overhead Elmo A305 SD 7300 lumens.
Overhead stage area = 126 sq in
8.4 in panel area = 33.9 sq in
10.2 in panel area = 49.9 sq in
33.9/126 = .27 or 27% .27 x 7300 = 1970 lumens
49.9/126 = .39 or 39% .39 x 7300 = 2850 lumens
The above is the amount of light that the panel sees. only about 10% to 15% of the light will pass through the panel. So an 8.4 in panel on a 7300 lumen projector will only output 200-300 lumens to the screen. The 10.2 in panel will only output 280-425 lumens.
A 7300 lumen overhead projector is a pretty high test projector. If you are using a more common lower output projector the output will be proportionally lower.
Another thing to consider. The luminous output spec'd for an overhead is the total output across the entire stage area. The projection panels only take up a small percentage of this area.
Example: Overhead Elmo A305 SD 7300 lumens.
Overhead stage area = 126 sq in
8.4 in panel area = 33.9 sq in
10.2 in panel area = 49.9 sq in
33.9/126 = .27 or 27% .27 x 7300 = 1970 lumens
49.9/126 = .39 or 39% .39 x 7300 = 2850 lumens
The above is the amount of light that the panel sees. only about 10% to 15% of the light will pass through the panel. So an 8.4 in panel on a 7300 lumen projector will only output 200-300 lumens to the screen. The 10.2 in panel will only output 280-425 lumens.
A 7300 lumen overhead projector is a pretty high test projector. If you are using a more common lower output projector the output will be proportionally lower.
Re: Overhead calcs.
Maybe the OHP retrofitters should start thing about how could they project the light beam from the lightsource just to the are the panel covers!
Regards
HB
Very good point!bixs said:
Maybe the OHP retrofitters should start thing about how could they project the light beam from the lightsource just to the are the panel covers!
Regards
HB
Why is the 36% of loss at the optics necessary in my case
Hi!
Some of you may think that "damn that guy is stupid, we all know this stuff already, it has been discussed on many threads before" but anyways...
I today on a bus to home with a new halogen for my projector (just a 150w FCS for a nighttime viewing, I'll get those 250w EVCs when I find a cheap transformer that can take them)... I looked at the lamp and then it came to me... "HEUREKA! IT WOULD NOT BE GOOD ANY OTHER WAY!"
Oh what would'nt be good? Well. The thing that brought me to this realization was the a bit randomly shaped small lump of glass on top of the halogen... and that is on top of about all halogens similar to this one..... so the light could not be even and as bright as it would be coming out of the sides of the lamp... and then I also made note that "Aaaaa...." there can't be a very efficient reflector at the bottom either as the lamp base is there, and the shape of the lamp is not very good at the bottom.
So, we could make a reflector to get more light from the sides of the thing and some from the top. The result would be about 30% brighter image at sides, something like 15-20% at bottom and dim looking upper part of the projected image... that really would look damn stupid. So in this kind of setup as mine it really cant be much better as it already is. 36% loss at the start is the cost for evenly bright image, I'll just have to live with that or make a comletely new setup so that the lamp base is at bottom of a reflector resulting in something like the FXL lamp has built in it already in the factory.
Regards
HB
Hi!
Some of you may think that "damn that guy is stupid, we all know this stuff already, it has been discussed on many threads before" but anyways...
I today on a bus to home with a new halogen for my projector (just a 150w FCS for a nighttime viewing, I'll get those 250w EVCs when I find a cheap transformer that can take them)... I looked at the lamp and then it came to me... "HEUREKA! IT WOULD NOT BE GOOD ANY OTHER WAY!"
Oh what would'nt be good? Well. The thing that brought me to this realization was the a bit randomly shaped small lump of glass on top of the halogen... and that is on top of about all halogens similar to this one..... so the light could not be even and as bright as it would be coming out of the sides of the lamp... and then I also made note that "Aaaaa...." there can't be a very efficient reflector at the bottom either as the lamp base is there, and the shape of the lamp is not very good at the bottom.
So, we could make a reflector to get more light from the sides of the thing and some from the top. The result would be about 30% brighter image at sides, something like 15-20% at bottom and dim looking upper part of the projected image... that really would look damn stupid. So in this kind of setup as mine it really cant be much better as it already is. 36% loss at the start is the cost for evenly bright image, I'll just have to live with that or make a comletely new setup so that the lamp base is at bottom of a reflector resulting in something like the FXL lamp has built in it already in the factory.
Regards
HB
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