Wow, 50% light increase, that's a really PRO reflector 🙂
Anyway, in my calculations I assumed 100% increase, and the result was still below 300lm, for 15" LCD and standard optics.
> and the 14% collecting... any further information to prove this?...
It's the geometry (assuming 15" LCD and 220mm fresnel). Tell me your number, so I would have a feeling what your opinion is. You only ask questions, but never give any answers.
Regards
Anyway, in my calculations I assumed 100% increase, and the result was still below 300lm, for 15" LCD and standard optics.
> and the 14% collecting... any further information to prove this?...
It's the geometry (assuming 15" LCD and 220mm fresnel). Tell me your number, so I would have a feeling what your opinion is. You only ask questions, but never give any answers.
Regards
well, "most effective reflector I have seen" sounds better to me as well.
I will answer to something when I am asked.
the LCD is 17" anyway, not 15".
assumtion;
*lcd flat area wil be considered as shperical surface. I know some error is introduced here.
*it is generally acepted in real lamps that total lumens/10 to be the average candelas output. if it was point source it would be /12.7 but the base and phsical limitations on real world shows /10 is a closer to reality value.
*PRO reflector is reflecting 50% light. So the fresnell facing candela on the output is 1.5 times the average candela.
we have 40klumens, so 4000 candelas is the average value.
If we introduce the reflector there, we have 6000 candelas on the way. The 17" is 0.09meters square area. The 6000 candelas will have 6000 lux value at 1 meter from the lamp---- 24Klux at 50cm------96Klux at 25cm---- lets say 100Klux at 22cm (let me know if you need further precision here).
Now just multply the 100Klux value with 0.09meters square area=
9000 lumens hitting the LCD. this is 22,5% of the total light available. Well this value is going to be something lesser because of spherical/flat error. Your 20% initial value was not far in may opinion.
I will answer to something when I am asked.
the LCD is 17" anyway, not 15".
assumtion;
*lcd flat area wil be considered as shperical surface. I know some error is introduced here.
*it is generally acepted in real lamps that total lumens/10 to be the average candelas output. if it was point source it would be /12.7 but the base and phsical limitations on real world shows /10 is a closer to reality value.
*PRO reflector is reflecting 50% light. So the fresnell facing candela on the output is 1.5 times the average candela.
we have 40klumens, so 4000 candelas is the average value.
If we introduce the reflector there, we have 6000 candelas on the way. The 17" is 0.09meters square area. The 6000 candelas will have 6000 lux value at 1 meter from the lamp---- 24Klux at 50cm------96Klux at 25cm---- lets say 100Klux at 22cm (let me know if you need further precision here).
Now just multply the 100Klux value with 0.09meters square area=
9000 lumens hitting the LCD. this is 22,5% of the total light available. Well this value is going to be something lesser because of spherical/flat error. Your 20% initial value was not far in may opinion.
I don't really understand this tricky idea of going from lumens to lux and candelas, and then back to lumens, while all you need to calculate is the solid angle contained in the intersection of LCD plane with a sphere. This would give you total number of collected lumens, without introducing extra errors, like assumption of spherical LCD surface. This solid angle is not that simple to calculate either, but it can be done and I did it once.
So you agree for 20% collected light with 17" LCD, this implies you also agree for 17% for a 15" LCD, don't you? And this is very close to my calculations, as far as I remember I calculated something about 23% or 24% for 100% efficient reflector. So 12% without reflector, so about 18% with a 50% efficient reflector. It's good our results are pretty close so far.
Now tell me please how do you get 5000lm out of the lens. Let's assume you have 8000lm after field fresnel (it's way too optimistic, but I assumed 8000lm before, so let's keep it). And f-stop value is around 5. Are you absolutely sure you know what f-stop means?
Regards
So you agree for 20% collected light with 17" LCD, this implies you also agree for 17% for a 15" LCD, don't you? And this is very close to my calculations, as far as I remember I calculated something about 23% or 24% for 100% efficient reflector. So 12% without reflector, so about 18% with a 50% efficient reflector. It's good our results are pretty close so far.
Now tell me please how do you get 5000lm out of the lens. Let's assume you have 8000lm after field fresnel (it's way too optimistic, but I assumed 8000lm before, so let's keep it). And f-stop value is around 5. Are you absolutely sure you know what f-stop means?
Regards
yes I agree somewhere 18% for 17". 7200 sounds realistic to me at this point (not optimistic).
mmm, now about F-stop, yes, I really know what it is, but start wondering if you know it...
There is no F-stop on the standar triplet lenses, neither on the PRO lens, in fact, there is no need of that in principle, since it is working in phograpic capturing to even the input light (making central light dimer)... it is not the case on a OHP or a DIY.
about 7200 lumes to 5000 effectivity on triplet, this is 70% effciieny on triplet side. Don´t you see it realistic either?
mmm, now about F-stop, yes, I really know what it is, but start wondering if you know it...
There is no F-stop on the standar triplet lenses, neither on the PRO lens, in fact, there is no need of that in principle, since it is working in phograpic capturing to even the input light (making central light dimer)... it is not the case on a OHP or a DIY.
about 7200 lumes to 5000 effectivity on triplet, this is 70% effciieny on triplet side. Don´t you see it realistic either?
Rox said:
Oh man, you claim there is no f-number value for projection lens? And its efficiency is whatever you desire to confirm some unrealistic statements? I have not much time to waste, but I found it for you, as you apparently don't know much about lenses (I don't know much either, but you seem to know less, so I share with you 🙂
http://www.broadwaypress.com/PDFs/LTSpdfs/LTSchpt16.pdf
scroll to page 7, there is a note on f-stop value.
Sure, there is no adjustable diaphragm in the projection lens, but definitely there is an f-number value, and in case of your lens it happens to be about 5. And value of 5 means rather dim lens (check the values for "real" projection systems, all of them are below f/2). Good for you if your f/5 lens passes 70% light, I don't know why not 90%? How much it will really pass - look yourself in the books or on the web, there are formulas for that, it's no way a "guess" value.
Regards
Long time no posts...
Hey pepe. Well, according to the readings from my luxmeter, a 50% increase is exactly what I got. 1020 lux from the lamp with no reflector, mounted in a box painted black. 1530 lux from the lamp at exactly the same distance and orientation with the reflector. I did everything that I could to eliminate other variables. These measurements were at a distance of 2m from the lamp.
I will not deny that commercial units are speced at higher lumens (Yes, even cheap ones) than what I currently measure. As is, I have more than I need. I was getting by on less than 1/2 of what I now have, and I was happy with that.
Hey pepe. Well, according to the readings from my luxmeter, a 50% increase is exactly what I got. 1020 lux from the lamp with no reflector, mounted in a box painted black. 1530 lux from the lamp at exactly the same distance and orientation with the reflector. I did everything that I could to eliminate other variables. These measurements were at a distance of 2m from the lamp.
I will not deny that commercial units are speced at higher lumens (Yes, even cheap ones) than what I currently measure. As is, I have more than I need. I was getting by on less than 1/2 of what I now have, and I was happy with that.
hello again;
So you only are triyng to ridiculize me or what?
YES, THERE IS NO F-STOP ON OUR PROJECTION LENSES.
I never said there was no F- number on a projection lens as you have said I did.
The F number for a lens is just the ratio of the Effective focal lengh/ effective lens aperture.
now a big question, DO you know what F-STOP is?
So you only are triyng to ridiculize me or what?
YES, THERE IS NO F-STOP ON OUR PROJECTION LENSES.
I never said there was no F- number on a projection lens as you have said I did.
The F number for a lens is just the ratio of the Effective focal lengh/ effective lens aperture.
now a big question, DO you know what F-STOP is?
Rox: you are playing with words, I'm not into it, as this is difficult in a foreign language. Just tell me please how much light will go through this lens with f/5, in your opinion. Why do you think it would be 70% of incoming light, just because it matches other numbers you quoted? You have 8000lm in, f/5, how many lm out?
And for some guy above, who suspected I haven't built a projector, or I got inferior results:
And for some guy above, who suspected I haven't built a projector, or I got inferior results:
Attachments
well, you just can´t work it out.
the F number (speed) will tell you how much of the light will be captured on a photograpic situation where there is OMNI light.
on the projector there is condensed light at triplet (field fresnell is doing that work, so ideally forgeting about arc sizes... the F number will not matter at all, in reall world a larger lens (smaller F) will do better work than a smaller F but this is because of the light spillage or arc size...
Ideally a light point will project same amount of lumens no matter what F projection lens you use.
there is no maths involved on that ideal case.
By the way, I never did word tricks, I knew what i was talking about... but I guess you use F number and F stop-- ramdonly no matter what you mean... Yes i agree when YOU say "I don´t know much about optics"
the F number (speed) will tell you how much of the light will be captured on a photograpic situation where there is OMNI light.
on the projector there is condensed light at triplet (field fresnell is doing that work, so ideally forgeting about arc sizes... the F number will not matter at all, in reall world a larger lens (smaller F) will do better work than a smaller F but this is because of the light spillage or arc size...
Ideally a light point will project same amount of lumens no matter what F projection lens you use.
there is no maths involved on that ideal case.
By the way, I never did word tricks, I knew what i was talking about... but I guess you use F number and F stop-- ramdonly no matter what you mean... Yes i agree when YOU say "I don´t know much about optics"
Pepe, can you explain to me what exactly you didnt like about the projector you built, by that one image it looks very nice. Of course your the one saying that camara tricks are always used right, so what tricks did you use?
btw I just played doom3 for about 5 hours in broad daylight on my buddies 800*600 homebrew projector. Granted the screen is only 90" but still, I would call that extremely cool.
btw I just played doom3 for about 5 hours in broad daylight on my buddies 800*600 homebrew projector. Granted the screen is only 90" but still, I would call that extremely cool.
Camman said:
My trick was to use quite a long exposure time. Not longer than other DIY projectors require, maybe total exposure was a bit lower than average, but still it's so high, that indicated severe shortage of light output from my projector. Camera settings used for the picture: ISO100, f/3.2, t=1.3s, screen is 2.9m wide (about 140" diagonal). These are settings typical for a night photography, while we watch a daylight scene.
I could also use the following popular tricks: contrast extension, colour enhancement, noise filtering (there is some camera noise, you can see it in black areas, but this does not exist in the real picture, so using this trick may be acceptable). And of course choosing a bright scene is always desirable.
Rox: sure, you are the right, just all manufacturers are wrong, and those who state the brightness of their projection lenses are loosers, as they quote meaningless numbers to fool the customers. In fact it does not matter if you have bright or dim lenses, all of them produce the same bright image, with efficiency as high as you wish. Maybe 70%, why not.
Look here http://www.projectorcentral.com/cc990212.htm and check for question on lens specifications. Sorry, I can't spend more time searching info for you, and you can certainly neglect any given information, as they always know better at some "private forums".
Regards
I said larger lens diameter was better pepe, or don´t you read what I post?
BUT this is because of light spillage arround the projeciton lens and is directly related to arc lengh as well...
IN IDEAL WORLD if we could focus the light at a point, THEN IT DOES NOT MATTER THE F NUMBER OF THE LENS.
The F number is more important in photographic capturing situations, OMNI light is hitting the objetive on those case, never hapening on our projectors. I believe the clear diameter of the triplet is more important value for us.
You are not the onlu one loosing time here.
BUT this is because of light spillage arround the projeciton lens and is directly related to arc lengh as well...
IN IDEAL WORLD if we could focus the light at a point, THEN IT DOES NOT MATTER THE F NUMBER OF THE LENS.
The F number is more important in photographic capturing situations, OMNI light is hitting the objetive on those case, never hapening on our projectors. I believe the clear diameter of the triplet is more important value for us.
You are not the onlu one loosing time here.
I think what you are both looking for is the T-number of the lens.
This indicates the transmissivity, and takes into account losses due to internal reflections, glass opacity etc.
This indicates the transmissivity, and takes into account losses due to internal reflections, glass opacity etc.
There is fundamental mistakes in perception of whole phenomena. In cameras, the light is entering from outside and the aperture becomes important for focussing the image. On the other end, in projectors the inside image passes through projection lensn without any control of aperature as the whole system is prefocussed. Hence the trasmission of light depends on the lens elements. In DIY projectors, there are normally 4 elements whereas in the commercial projectors there may be 12 or more elements. Hence the loss of light in projection lens combinations in commercial projectors is more than DIY projectors.
well I think the head of pepe303 and Rox has been done in the same metal 
😉
pepe, I agree that as when you decide to buy a commercial pj the brigthness is certainly an important point. And i'm not sure that a lot of people will buy a commercial pj anounced for 100 or 200 lumens.
In addition, you find now ship projector. i have seen recently a brand new tri-lcd pj in 800*600 for 380euros lumen output was 1000lumens (checked by luxmeter measurement by someone on the french diy pj site). So doing a diy pj with a lilliput is more for fun than to save money.
However since i got my diy pj (800*600) I have a lot of fun and i watch a lot of think. I got right now 180 lumens output at the center and i use a glass beaded screen. I 'm doing the final box righ now and the pj is in my garage for the last 3 week and i miss it.
I think that 180lumens for a 2m base picture is largely enough to watch movie at night.
The point is that moving from 100 lumens to 180 give me less contrast and i think this is the worst point.
Concerning , HD pj. You can do something great for 500Euros. Again the main use will be at night. However, the 400 lumens value is something that you can obtain with a 17" lcd and a 40000 lumnes bulb. Again with 2m base picture and a gain screen, you'll get very good result to watch with some light around. The only point is that you should consider that you'll have a very big box in your living room. If you can integrate this in your living room, you'll have something fun. Bigger lcd , bigger ligh ouput but also dimmer corner. The main point on the 400lumens setting is the 8.8% transmissivity of the LCD which is a huge difference with the 5% average of lcd (I would be interested in knowing the name and brand of this lcd?)
Concerning the fact that LCd projector are old junk, you have to consider 2 systems:
the old lcd projector (identical setting then from our diy pj) well you know them.
the new tri-lcd projector based on 0.7-1.2" htps lcd which are still competing with dlp (see the hitachi pj-tx200 or sanyo plv z4 or panasonic pt-ae900). All of them are made with epson d5 htps lcd 0.7" 1280*720. epson is developping the 0.7" 1920*1080 htps lcd for this year.
So lcd projector are not dead. Then how they manage to improve the brightness (which is lower than dlp for physical reason) and also the contrast (which was very bad for the old lcd projector 100-300:1 max).
Mainly they have powelful bulb but with short life. Reflector which seem to be parabolic and bigger than the htps lcd.
The light is then process through 2 fresnels arrays (yes all these have fresnel array to decrease dim corner) .
They use a polarization changer element (kind of the reverse of an antiglare) which put the light wich is not polarized in the right plane and usually reflected in the good plane (then transmitted): improvemnt of brigtness between 1.4 and 1.9 factor
Then they use specific layer on the lcd to redirecd the light which hit the grid and are usually not tranmit and gain again 1.5 factor.
So 1.5 by 1.5 they get high lumens output.
Then they work also on the contrast by using diaphragm (iris).
Static iris on the projection lens and dynamic iris just after the bulb.
Dynamyc iris means that when the picture is dark they close the iris and when this is white they open it. So they get 4000:1 contrast value....
concerning the projection lens they have around 10 to 15 lens inside. I think that as say dnsey this is to improve the t number of the lens. So yes the is projection lens and projection lens. Let assume that we loose around 20% in our diy setting(at least this is the case in mine where all the ligh enter the lens).
There is always a way to improve a system, you just have to know how much time effort and money you want to spend to do it!!! Sometimes private companies let on the side the better technics just because the marketing is better for the worst one.
Right now, I'm thinking to put a static iris on my projection lens in order to increase the contrast for movies in the dark since the lumen output is largely enough.
So to come back to the initial topic, to increase brightness use small arc bulb with big lumen output, good reflector and precondensor lens, short focal condenser fresnel, projection lens with a diameter big enough according to your setting and a highly transmissive 17" lcd without antiglare if this one is a bad one. This way you might have a diy pj with a max lumen output of 400! that's it.
Now if 400 lumens is not enough for you just buy a commercial one.
😉 pepe, I agree that as when you decide to buy a commercial pj the brigthness is certainly an important point. And i'm not sure that a lot of people will buy a commercial pj anounced for 100 or 200 lumens.
In addition, you find now ship projector. i have seen recently a brand new tri-lcd pj in 800*600 for 380euros lumen output was 1000lumens (checked by luxmeter measurement by someone on the french diy pj site). So doing a diy pj with a lilliput is more for fun than to save money.
However since i got my diy pj (800*600) I have a lot of fun and i watch a lot of think. I got right now 180 lumens output at the center and i use a glass beaded screen. I 'm doing the final box righ now and the pj is in my garage for the last 3 week and i miss it.
I think that 180lumens for a 2m base picture is largely enough to watch movie at night.
The point is that moving from 100 lumens to 180 give me less contrast and i think this is the worst point.
Concerning , HD pj. You can do something great for 500Euros. Again the main use will be at night. However, the 400 lumens value is something that you can obtain with a 17" lcd and a 40000 lumnes bulb. Again with 2m base picture and a gain screen, you'll get very good result to watch with some light around. The only point is that you should consider that you'll have a very big box in your living room. If you can integrate this in your living room, you'll have something fun. Bigger lcd , bigger ligh ouput but also dimmer corner. The main point on the 400lumens setting is the 8.8% transmissivity of the LCD which is a huge difference with the 5% average of lcd (I would be interested in knowing the name and brand of this lcd?)
Concerning the fact that LCd projector are old junk, you have to consider 2 systems:
the old lcd projector (identical setting then from our diy pj) well you know them.
the new tri-lcd projector based on 0.7-1.2" htps lcd which are still competing with dlp (see the hitachi pj-tx200 or sanyo plv z4 or panasonic pt-ae900). All of them are made with epson d5 htps lcd 0.7" 1280*720. epson is developping the 0.7" 1920*1080 htps lcd for this year.
So lcd projector are not dead. Then how they manage to improve the brightness (which is lower than dlp for physical reason) and also the contrast (which was very bad for the old lcd projector 100-300:1 max).
Mainly they have powelful bulb but with short life. Reflector which seem to be parabolic and bigger than the htps lcd.
The light is then process through 2 fresnels arrays (yes all these have fresnel array to decrease dim corner) .
They use a polarization changer element (kind of the reverse of an antiglare) which put the light wich is not polarized in the right plane and usually reflected in the good plane (then transmitted): improvemnt of brigtness between 1.4 and 1.9 factor
Then they use specific layer on the lcd to redirecd the light which hit the grid and are usually not tranmit and gain again 1.5 factor.
So 1.5 by 1.5 they get high lumens output.
Then they work also on the contrast by using diaphragm (iris).
Static iris on the projection lens and dynamic iris just after the bulb.
Dynamyc iris means that when the picture is dark they close the iris and when this is white they open it. So they get 4000:1 contrast value....
concerning the projection lens they have around 10 to 15 lens inside. I think that as say dnsey this is to improve the t number of the lens. So yes the is projection lens and projection lens. Let assume that we loose around 20% in our diy setting(at least this is the case in mine where all the ligh enter the lens).
There is always a way to improve a system, you just have to know how much time effort and money you want to spend to do it!!! Sometimes private companies let on the side the better technics just because the marketing is better for the worst one.
Right now, I'm thinking to put a static iris on my projection lens in order to increase the contrast for movies in the dark since the lumen output is largely enough.
So to come back to the initial topic, to increase brightness use small arc bulb with big lumen output, good reflector and precondensor lens, short focal condenser fresnel, projection lens with a diameter big enough according to your setting and a highly transmissive 17" lcd without antiglare if this one is a bad one. This way you might have a diy pj with a max lumen output of 400! that's it.
Now if 400 lumens is not enough for you just buy a commercial one.
someone get a lux meter - and do some testing - there only
$40 -
DIY works good - its not perfect - but who wants to pay
$300 or more for a lamp
My crappy DIY projector with a burnt-up frensel,
and condenser lens from a slide projector thats
not the right focal distance - is still watchable
with 2 40watt flo lights on over head - and all I got
is a 250w HQI and a soup ladel reflector - that
turns gold from the heat every few months
and a 10 year old LCD - 640X480 rez
now just think if I had a good frensel,
condenser lens, a 400w lamp,
and 15in high rez LCD
yep thats me - do you hear me now?? 😉
$40 -
DIY works good - its not perfect - but who wants to pay
$300 or more for a lamp
My crappy DIY projector with a burnt-up frensel,
and condenser lens from a slide projector thats
not the right focal distance - is still watchable
with 2 40watt flo lights on over head - and all I got
is a 250w HQI and a soup ladel reflector - that
turns gold from the heat every few months
and a 10 year old LCD - 640X480 rez
now just think if I had a good frensel,
condenser lens, a 400w lamp,
and 15in high rez LCD
yep thats me - do you hear me now?? 😉
According to what I have read, and the best lumen output to date, we are getting roughly 1% final lumen output to the wall. From a 40,000 lumen light, he gets a little over 400 lumens. So we need a light that generates say 120,000 lumens to get a good comparable output. Am I correct? Most of the projector replacement lights I am finding are 1000w to 3000w lights. No wonder they put out 1000 lumens. I think if we can find a small arc 1500w light, we would be in business.
Actually, most DIY projectors will output a little less than 200 lumens. The highest I've seen is 400 lumens.
This is more than acceptable for home viewing. A typical movie theater brightness is about 100 lumens per square meter. So if your screen is 1.5 sqaure meters then 150 lumens should be sufficient for general viewing. Above that and you can use more ambient lighting. If you're outputting around 200 lumens and your screen is 72" diagonal (4:3 ratio) then you will have more than enough brightness to watch regular TV with the lights on.
Commercial projectors that state outputs of 1000 lumens are just using that as a marketing gimmick. The excess brightness is not usually needed for home viewing unless you plan to have a huge screen.
This is more than acceptable for home viewing. A typical movie theater brightness is about 100 lumens per square meter. So if your screen is 1.5 sqaure meters then 150 lumens should be sufficient for general viewing. Above that and you can use more ambient lighting. If you're outputting around 200 lumens and your screen is 72" diagonal (4:3 ratio) then you will have more than enough brightness to watch regular TV with the lights on.
Commercial projectors that state outputs of 1000 lumens are just using that as a marketing gimmick. The excess brightness is not usually needed for home viewing unless you plan to have a huge screen.
I tried posting a pic of the brightness of my projector
and it was a timed pic and the phone rang and I picked it
up just before the cam snaped the pic - I was standing
in front of the screen
thats why I posted
"yep thats me - do you hear me now?? "
but I dont see it
but yea mine is about 72" diagonal and is a (4:3 ratio)
screen
it helps having the walls around the screen dark
but yea I have the lights on all the time
and it was a timed pic and the phone rang and I picked it
up just before the cam snaped the pic - I was standing
in front of the screen
thats why I posted
"yep thats me - do you hear me now?? "
but I dont see it
but yea mine is about 72" diagonal and is a (4:3 ratio)
screen
it helps having the walls around the screen dark
but yea I have the lights on all the time
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