all i want is to watch dvd's but will "Resolution (W x H): 480 x 234 pixels " even be good enough for that @6' diaginal? i was wanting at least 640/480 then cheap scaler or even scecond vid card
Darth Willis does have a point. But I think that he is missing ours. You guys are being a little hard on him. I mean, all he did was sum up most of the problems that the old timers on this thread have come across. And lets face it, It is never bad to have a doom sayer in the ranks. In fact it usualy will push someone in another direction that might work better. But I digress.
What Darth Willis is trying to say is that this project is not for the faint of heart(or wallet) And we all know that there are MANY technical problems to overcome.
Our point is, We don't care why it won't work. Our goal is to get around "why it won't work" and make it work. And if someone learns something in the process then this thread has done its job.
What Darth Willis is trying to say is that this project is not for the faint of heart(or wallet) And we all know that there are MANY technical problems to overcome.
Our point is, We don't care why it won't work. Our goal is to get around "why it won't work" and make it work. And if someone learns something in the process then this thread has done its job.
Darth...dont run off so soon!!!
I agree with you that people really seemed to jump on you a bit. I think your original post did have some valid information and got people talking about light recycling again. The problem is this...
Your post seemed to come off on people as we were wasting our time and this cant be done because you proved us wrong. Our orignal responses were interest in your project...and once someone brought up your scepticism (dude I cant spell OK) everything seemed to snowball from there. Dont worry about it.
You have to realize though that there are a number of different people on this board. Since I fall into a number of categories I think I can explain...
-- first you have the people who came here in response to the 100" TV and are more than thrilled to have a 100" LCD projector for $100 that is WAY!!!!!! better than the stupid 100" TV. These people see your post and say..."$hit...I already made my projector for $100...whats he talking about". They are very happy and content with what they have or are building. Eventually they will probably want more and use this board to enhance their system.
-- second you have the people who are trying to get a very nice picture out of their system. They are interested in the lighting aspects, the contrast, the optics, etc... These people are here to learn different cheap-home-hacked solutions to get a great image at LOW cost. The idea is to spend less than 20% of the money for an equivilant picture. Most are not concerned wether their system is portable, is pretty, or has any bells and whistles...They just want a large, bright, and crisp image for low money. Right now there is nothing on the market that offers this. everything is small, portable, has a bunch of features that are nice but not necessary for home use, and are VERY expensive. These are the people that see this as a hobby. It's their hobby and thats what they enjoy doing...The like to find better cheaper ways to do things and be the one that came up with the idea or found the link that we all use...When you tell us that we are basically wasting our time people are going to be defensive...thats like telling a surfer he is never going to find the perfect wave or recreational runner he is never going to be in the Olympics so why bother...people enjoy what they do and many of us may end up spending A LOT of money...I for one am probably going to be one of those people as I try out many things...but I do want to be someone who can say..."Hey look at what I made Ma!!!" I like that...I live for that...and take pride in making something myself...I am quite certain most others on this group are the same...they want to be able to say...look....I made this from hand...I ROCK!!!
Dont knock people for that...they are not here to save the world from the evil projector empire...We want your input and knowledge but dont make them feel you're telling them they are wrong for doing what they are doing...If I spend $1500 to build my projector in a million stages and can come up with a plan for others to build for $300 I will be very happy because other people will be using my ideas.
The last group of people are the people here that are out to find the NEW solutions. When you infer it cant be done it just pisses them off more and makes them want to prove you wrong....These people are out to find the cutting edge new solution to projection and together we will hopefully find it. If we can obtain the knowledge and resources to built entry level projectors that dont have a million bells and whistled we will be happy. And it can be done.
SOOO...I hope you can understand how your intial comments have snowballed into a misunderstanding of what you were saying. I for one dont want you to quit and leave. You obviously have knowledge on the subject matter...unfortunately you just have too much scepticism. I argue all the time with friends that say I couldnt accomplish what I have already done. Just keep in mind that the second paragraph of your last post is EXACTLY what a lot of people want to do...at least I do. So try not to let our home made, half baked ideas get to you. Just help us move on to the next level.
Sorry to ramble on so much...I just felt that he was getting a little missunderstood and wanted to keep him around befor we chased him off.
Later...and good luck everyone.
Dave
I agree with you that people really seemed to jump on you a bit. I think your original post did have some valid information and got people talking about light recycling again. The problem is this...
Your post seemed to come off on people as we were wasting our time and this cant be done because you proved us wrong. Our orignal responses were interest in your project...and once someone brought up your scepticism (dude I cant spell OK) everything seemed to snowball from there. Dont worry about it.
You have to realize though that there are a number of different people on this board. Since I fall into a number of categories I think I can explain...
-- first you have the people who came here in response to the 100" TV and are more than thrilled to have a 100" LCD projector for $100 that is WAY!!!!!! better than the stupid 100" TV. These people see your post and say..."$hit...I already made my projector for $100...whats he talking about". They are very happy and content with what they have or are building. Eventually they will probably want more and use this board to enhance their system.
-- second you have the people who are trying to get a very nice picture out of their system. They are interested in the lighting aspects, the contrast, the optics, etc... These people are here to learn different cheap-home-hacked solutions to get a great image at LOW cost. The idea is to spend less than 20% of the money for an equivilant picture. Most are not concerned wether their system is portable, is pretty, or has any bells and whistles...They just want a large, bright, and crisp image for low money. Right now there is nothing on the market that offers this. everything is small, portable, has a bunch of features that are nice but not necessary for home use, and are VERY expensive. These are the people that see this as a hobby. It's their hobby and thats what they enjoy doing...The like to find better cheaper ways to do things and be the one that came up with the idea or found the link that we all use...When you tell us that we are basically wasting our time people are going to be defensive...thats like telling a surfer he is never going to find the perfect wave or recreational runner he is never going to be in the Olympics so why bother...people enjoy what they do and many of us may end up spending A LOT of money...I for one am probably going to be one of those people as I try out many things...but I do want to be someone who can say..."Hey look at what I made Ma!!!" I like that...I live for that...and take pride in making something myself...I am quite certain most others on this group are the same...they want to be able to say...look....I made this from hand...I ROCK!!!
Dont knock people for that...they are not here to save the world from the evil projector empire...We want your input and knowledge but dont make them feel you're telling them they are wrong for doing what they are doing...If I spend $1500 to build my projector in a million stages and can come up with a plan for others to build for $300 I will be very happy because other people will be using my ideas.
The last group of people are the people here that are out to find the NEW solutions. When you infer it cant be done it just pisses them off more and makes them want to prove you wrong....These people are out to find the cutting edge new solution to projection and together we will hopefully find it. If we can obtain the knowledge and resources to built entry level projectors that dont have a million bells and whistled we will be happy. And it can be done.
SOOO...I hope you can understand how your intial comments have snowballed into a misunderstanding of what you were saying. I for one dont want you to quit and leave. You obviously have knowledge on the subject matter...unfortunately you just have too much scepticism. I argue all the time with friends that say I couldnt accomplish what I have already done. Just keep in mind that the second paragraph of your last post is EXACTLY what a lot of people want to do...at least I do. So try not to let our home made, half baked ideas get to you. Just help us move on to the next level.
Sorry to ramble on so much...I just felt that he was getting a little missunderstood and wanted to keep him around befor we chased him off.
Later...and good luck everyone.
Dave
tech_head
tech_head...whooo it sounds like we were thinking basically the same thing. I just took 30 minutes to write my response here at work...I finish it..post it...and you said the same thing in 4 lines...LOL
everyone else...Has anyone worked with molding/forming plastic?I have a dream of molding my own parabolic reflector and then getting it electroplated. Dont laugh!!!! I would like to be able to pour liquid plastic (or other substance) over a parabolic mold to create a solid object. I originally thought I could make it out of bondo but I dont think that bondo will survie the electroplating process...so I would basically like to build my own reflector and electroplate it(or however else I can make it really shiny...IDEAS PLEASE??). I want it to look like the reflector inside a flashlight or car headlight...you know...even the LCD projector lamps are like this. Any ideas?
To summarize I would like info on molding plastic and electroplating(or other method) to make it as close to 100% reflective as possible...
Thanks,
Dave
tech_head...whooo it sounds like we were thinking basically the same thing. I just took 30 minutes to write my response here at work...I finish it..post it...and you said the same thing in 4 lines...LOL
everyone else...Has anyone worked with molding/forming plastic?I have a dream of molding my own parabolic reflector and then getting it electroplated. Dont laugh!!!! I would like to be able to pour liquid plastic (or other substance) over a parabolic mold to create a solid object. I originally thought I could make it out of bondo but I dont think that bondo will survie the electroplating process...so I would basically like to build my own reflector and electroplate it(or however else I can make it really shiny...IDEAS PLEASE??). I want it to look like the reflector inside a flashlight or car headlight...you know...even the LCD projector lamps are like this. Any ideas?
To summarize I would like info on molding plastic and electroplating(or other method) to make it as close to 100% reflective as possible...
Thanks,
Dave
Go Darth!!
I have been pretty quiet since the arrival of our pal Darth, and I notice so has Mr.Mountain who has yet to back up his fantastic claims of LED projectors. Mind you, the laser thread is pretty good and I've not finished reading it yet. If you're still there Mountain boy get your balls out your pocket and back-up your post.
I was pretty impressed to read Darth's first post - he came out with some very valid points and anyone who has a tantrum at him for pointing out what we really already knew shouldn't be on the forum. Remember that this is a 'discussion' board. I only wish I'd rallied to his support earlier, but I had no time.
As for his points, I think we already knew most of them already. All he did was put them forward as more of a problem than some people appreciate.
I don't think you should just throw more light at the problem and hope this fixes it. Remember when you were little you had the "fit the square peg in the square hole" toy? If it went in the round hole, did you just hammer it harder until it fitted? Nope, you put it into the right hole.
Now, back to business. The forum is getting pretty dull - I think we need another forum called "DIY Video Projector - Stuff people actually want to know" and we could see a new post on it maybe once a week when something new and interesting is posted. Like Darth or Mountain - they're definitely the most interesting things to come out of this forum in ages.
I'm going to get on with my CRT projector quietly in the background and if anyone wants any CRT info then get in touch.
In the meantime, if anyone new dares to say something interesting, don't shoot them down. Darth does have a very good point about the difference between a projector and an ugly oversized box which makes an image on the wall.
I have been pretty quiet since the arrival of our pal Darth, and I notice so has Mr.Mountain who has yet to back up his fantastic claims of LED projectors. Mind you, the laser thread is pretty good and I've not finished reading it yet. If you're still there Mountain boy get your balls out your pocket and back-up your post.
I was pretty impressed to read Darth's first post - he came out with some very valid points and anyone who has a tantrum at him for pointing out what we really already knew shouldn't be on the forum. Remember that this is a 'discussion' board. I only wish I'd rallied to his support earlier, but I had no time.
As for his points, I think we already knew most of them already. All he did was put them forward as more of a problem than some people appreciate.
I don't think you should just throw more light at the problem and hope this fixes it. Remember when you were little you had the "fit the square peg in the square hole" toy? If it went in the round hole, did you just hammer it harder until it fitted? Nope, you put it into the right hole.
Now, back to business. The forum is getting pretty dull - I think we need another forum called "DIY Video Projector - Stuff people actually want to know" and we could see a new post on it maybe once a week when something new and interesting is posted. Like Darth or Mountain - they're definitely the most interesting things to come out of this forum in ages.
I'm going to get on with my CRT projector quietly in the background and if anyone wants any CRT info then get in touch.
In the meantime, if anyone new dares to say something interesting, don't shoot them down. Darth does have a very good point about the difference between a projector and an ugly oversized box which makes an image on the wall.
Matter of perception?
Funny how one person says "Impressive image" while another says "looks like it's come out of a 30 year old ViewMaster Projector" - whatever that looks like. Of course, they couldnt back up this ascertation with an actual image of what is crap vs what is good - to them - that we all can see.
The statment "A video projector is unfortunately a project not worth doing as a DIY unless you like trying to learn optics the hard way, flush money down the toilet and only want to build a $200-500+ "Gee-whiz Ma! Lookie whut I maeeed!" toy." ascribes value only in terms of what one person perceives. Sounds like the makings of some kind of religious war to me.
Like I'm trying to say - show me the images. Let's see what a 320X240 1.8" can do @ 6ft - and all the other resolutions/image sizes - and let the participants choose, based on their own perceptions, what is "worth" doing. Clearly one guy doesnt think the 640X480 panel with 1.4M colors is worthwhile, another does.
(I wonder what they'd think of my 1024X768 image?)
Funny how one person says "Impressive image" while another says "looks like it's come out of a 30 year old ViewMaster Projector" - whatever that looks like. Of course, they couldnt back up this ascertation with an actual image of what is crap vs what is good - to them - that we all can see.
The statment "A video projector is unfortunately a project not worth doing as a DIY unless you like trying to learn optics the hard way, flush money down the toilet and only want to build a $200-500+ "Gee-whiz Ma! Lookie whut I maeeed!" toy." ascribes value only in terms of what one person perceives. Sounds like the makings of some kind of religious war to me.
Like I'm trying to say - show me the images. Let's see what a 320X240 1.8" can do @ 6ft - and all the other resolutions/image sizes - and let the participants choose, based on their own perceptions, what is "worth" doing. Clearly one guy doesnt think the 640X480 panel with 1.4M colors is worthwhile, another does.
(I wonder what they'd think of my 1024X768 image?)
jjasniew...I like your picture a page or two back...looks GREAT for a broadcast image.
I'm sorry if you mentioned this befor but what OHP are you using that has 7K lumens?
Also, you say the image is wall size...aproximately how big is that?
It looks big to me and I'm getting excited.
How dark is your room with that image quality?
And one last thing...Can you get a decent (in your opinion) image with a lot of ambient light in the room?
Thanks,
Dave
I'm sorry if you mentioned this befor but what OHP are you using that has 7K lumens?
Also, you say the image is wall size...aproximately how big is that?
It looks big to me and I'm getting excited.
How dark is your room with that image quality?
And one last thing...Can you get a decent (in your opinion) image with a lot of ambient light in the room?
Thanks,
Dave
support? *gasp*
Thank you tech head, SuperDave and Scot_lad. I do apologize for coming off a bit harsh and am sorry if it rubbed you a bit of the wrong way. No hard feelings?
I think the easiest solution to overcoming the passthrough method is to change how you think of the LCD screen. The LCD isn't a transparancy... it's a lens, and it should be treated as such. The reasons why so much light is having to be thrown at it is for that reason. LCD screens only pass light in one direction due to the polarizers, something I might add is something that is necessary to have so the LCD panels work to begin with.
There have been some good things thrown out, but nobody is combining the right fiddly bits.
Dragonhalf was onto something with his link to the Nasa article on light recycling with LCD panels, but I don't think it's necessary. It'll be great to use to improve efficiency, but a sucessful projector needs to be built before thinking about optimization.
Anyway, from what I've seen so far and what I know, I think I have a good bead on what exactly would be needed to make the passthrough method to work with the LCD screens.
First, the light source. Instead of doing any focusing of far off light from a tiny source blown up, might I suggest going with a light box method instead. Going the route of cold cathode lighting with white bulbs that hit around 5000°K might be your best bet. They kick off around 500-700 lumens per foot (depending on quality), have a life of 1000-3000 hours (again, depending on quality of tubes plus the quality of power source) and run relatively cool. You can usually get them for around $5-7 a piece for the 12" tubes if you're willing to build the inverter yourself. Best place to look for this is from the computer mod community. The secret here is to get a large patch of light already going straight before hitting the LCD panel. I don't think the filiment based single light source methods are going to work on this scale because the light going into the LCD panel needs to be as straight as possible at point of contact. There of course will be slight problems with even light dispersion, but it might be remedied relatively easy by mirroring the back halves of the tubes, building curved reflectors and/or playing with light distances and spacing.
I have a feeling that good OHP optics will actually work. The scale is right for the size of image source to be used. The problem is though, in order for the OHP to work efficiently, it needs to have the light from the image source focused down to the projection head. Normally, this is done with the fresnel lens that would sit under the transparancies, but we can't use that because we need the light under the LCD to go as straight as possible before hitting it. So, that means the light focusing lens now has to focus both the light and the image down for the projection lens. This is where it's going to get expensive. If you have an LCD screen with a 9" diagonal, you're going to need an optical quality lens around 10-11" in diameter to do this with to keep the distortion to a minimum. Plus you'll need to build a light box around the LCD panel and this lens to keep as much light as possible.
Something else to consider... my guess is that most all of the LCD panels being used have anti-glare surfaces on the fronts of them. This is scattering the light and unneeded for a project like this. The best bet would be to either try and remove the film without damaging the screen or try and polish out the anti-glare surface. Either way is going to be rough, but I'm not sure how much of a benefit this might have.
A configuration like this should work in daylight with around 3-4000 lumens at the light source because the light will actually be used efficiently. Plus, it should eliminate the hot spot in the center and the dark ring around the edges because all the light is going in the right direction now. The theories are pretty sound, but I can't try them due to the prohibitive cost of a focusing lens nearly a foot in size. Fresnels might work, but you're going to lose a lot of image quality... so it's probably not worth it.
There's my two cents on the idea. Take it for what it's worth.
SuperDave, might I suggest going a slightly lower tech method of mirroring. Try using high gloss chrome paint from an auto store. With some trial and error, some extremely high numbered grit wet sanding and some turtle wax, you might get pretty close to what you're looking for. Good for a small job, bad for mass production. 🙄
...and yes, I know just enough optics to get myself in trouble. 😀
Thank you tech head, SuperDave and Scot_lad. I do apologize for coming off a bit harsh and am sorry if it rubbed you a bit of the wrong way. No hard feelings?
I think the easiest solution to overcoming the passthrough method is to change how you think of the LCD screen. The LCD isn't a transparancy... it's a lens, and it should be treated as such. The reasons why so much light is having to be thrown at it is for that reason. LCD screens only pass light in one direction due to the polarizers, something I might add is something that is necessary to have so the LCD panels work to begin with.
There have been some good things thrown out, but nobody is combining the right fiddly bits.
Dragonhalf was onto something with his link to the Nasa article on light recycling with LCD panels, but I don't think it's necessary. It'll be great to use to improve efficiency, but a sucessful projector needs to be built before thinking about optimization.
Anyway, from what I've seen so far and what I know, I think I have a good bead on what exactly would be needed to make the passthrough method to work with the LCD screens.
First, the light source. Instead of doing any focusing of far off light from a tiny source blown up, might I suggest going with a light box method instead. Going the route of cold cathode lighting with white bulbs that hit around 5000°K might be your best bet. They kick off around 500-700 lumens per foot (depending on quality), have a life of 1000-3000 hours (again, depending on quality of tubes plus the quality of power source) and run relatively cool. You can usually get them for around $5-7 a piece for the 12" tubes if you're willing to build the inverter yourself. Best place to look for this is from the computer mod community. The secret here is to get a large patch of light already going straight before hitting the LCD panel. I don't think the filiment based single light source methods are going to work on this scale because the light going into the LCD panel needs to be as straight as possible at point of contact. There of course will be slight problems with even light dispersion, but it might be remedied relatively easy by mirroring the back halves of the tubes, building curved reflectors and/or playing with light distances and spacing.
I have a feeling that good OHP optics will actually work. The scale is right for the size of image source to be used. The problem is though, in order for the OHP to work efficiently, it needs to have the light from the image source focused down to the projection head. Normally, this is done with the fresnel lens that would sit under the transparancies, but we can't use that because we need the light under the LCD to go as straight as possible before hitting it. So, that means the light focusing lens now has to focus both the light and the image down for the projection lens. This is where it's going to get expensive. If you have an LCD screen with a 9" diagonal, you're going to need an optical quality lens around 10-11" in diameter to do this with to keep the distortion to a minimum. Plus you'll need to build a light box around the LCD panel and this lens to keep as much light as possible.
Something else to consider... my guess is that most all of the LCD panels being used have anti-glare surfaces on the fronts of them. This is scattering the light and unneeded for a project like this. The best bet would be to either try and remove the film without damaging the screen or try and polish out the anti-glare surface. Either way is going to be rough, but I'm not sure how much of a benefit this might have.
A configuration like this should work in daylight with around 3-4000 lumens at the light source because the light will actually be used efficiently. Plus, it should eliminate the hot spot in the center and the dark ring around the edges because all the light is going in the right direction now. The theories are pretty sound, but I can't try them due to the prohibitive cost of a focusing lens nearly a foot in size. Fresnels might work, but you're going to lose a lot of image quality... so it's probably not worth it.
There's my two cents on the idea. Take it for what it's worth.
SuperDave, might I suggest going a slightly lower tech method of mirroring. Try using high gloss chrome paint from an auto store. With some trial and error, some extremely high numbered grit wet sanding and some turtle wax, you might get pretty close to what you're looking for. Good for a small job, bad for mass production. 🙄
...and yes, I know just enough optics to get myself in trouble. 😀
Re: Matter of perception?
You say potato, I say potatoe? Nothing like a little reality/negativiti to shake up the forum huh? I've read all the posts from the beginning (great job working at at Internet company that isn't bellyup!!) Darth just restated all the technical challenges (many yet unmet) that have been brought up before. On the subject of subjectivity. When CRT projection systems were first out, they were fuzzy, dim and cumbersome. They were also expensive. It didn't stop a lot of folks from buying them. Think about that when you see some of the better screen shots on this forum. There was still a gee whiz factor and people were shelling out the dough to sit in darkened rooms and (after fiddling with the convergence, adjusting the screen, etc) watch those dim and fuzzy dinosaurs. Just my two cents.
Also, to Mr. Bright Diode dude. Don't make us have to hunt you down like a rabid dog. Come off of some screen shots of your own, otherwise I'm thinking most of us will just assume you're full of bullsquat.
Enjoy.
You say potato, I say potatoe? Nothing like a little reality/negativiti to shake up the forum huh? I've read all the posts from the beginning (great job working at at Internet company that isn't bellyup!!) Darth just restated all the technical challenges (many yet unmet) that have been brought up before. On the subject of subjectivity. When CRT projection systems were first out, they were fuzzy, dim and cumbersome. They were also expensive. It didn't stop a lot of folks from buying them. Think about that when you see some of the better screen shots on this forum. There was still a gee whiz factor and people were shelling out the dough to sit in darkened rooms and (after fiddling with the convergence, adjusting the screen, etc) watch those dim and fuzzy dinosaurs. Just my two cents.
Also, to Mr. Bright Diode dude. Don't make us have to hunt you down like a rabid dog. Come off of some screen shots of your own, otherwise I'm thinking most of us will just assume you're full of bullsquat.
Enjoy.
LCD panel as a lens
Darth
You are right about the lcd panel being a lens. However, most of the people on this thread are using panels intended for use on an ohp. The light on an ohp doesn't come out entirely parallel and these panels were designed with that in mind. That is why they only have ~100:1 contrast ratio. The polarizers were intentionaly made lower quality to allow more light to pass through the panel. I believe that that is the reason that people are getting "less than adequate" results when using lcd monitors with ~250:1 contrast.
Darth
You are right about the lcd panel being a lens. However, most of the people on this thread are using panels intended for use on an ohp. The light on an ohp doesn't come out entirely parallel and these panels were designed with that in mind. That is why they only have ~100:1 contrast ratio. The polarizers were intentionaly made lower quality to allow more light to pass through the panel. I believe that that is the reason that people are getting "less than adequate" results when using lcd monitors with ~250:1 contrast.
Very true tech head, but I noticed that even those screens still suffer from the hot center and dim edges... that's why I don't think they ever caught on to begin with. Too low an image quality... this is yet another reason why I don't see it as worth it. Brute forcing your way around limitations might work to a degree, but it's no substitute for doing it right.
To make it worth doing, the end result in my opinion needs to have a contrast ratio around 200:1 minimum and an image resolution of at least 800x600 native... but YMMV. Again, I'm one of those looking at wanting professional results.
To make it worth doing, the end result in my opinion needs to have a contrast ratio around 200:1 minimum and an image resolution of at least 800x600 native... but YMMV. Again, I'm one of those looking at wanting professional results.
I did think about using the chrome paint...However, I was told and I also read somewhere that the chrome paint will sometimes look OK if you do and EXCELLENT job spraying...but if you try to polish it or even clearcoat it, it turns into a very dull grey. I have used a cheap can about 8 years ago when I was in highschool and I though I was going to paint my bike chrome (HA what a disaster). I think I might go out and get a decent can and see what I can do if it works that will be Great for what I want to do.
Now remember...for the time being I dont care if I have a ugly beast of a projector...I can make it pretty and small later...What I want to do is use the technique for drawing an elipse around 2 focal points. I will sketch this onto a thin piece of plywood and cut out a flat, eliptical shape. If I can get a bucket of bondo or other material I can set it up so I can rotate the plywood elipse circularly inside the bondo mixture and after a while have a fairly accurate ellipsoidal reflctor cast. Then, depending on if I make a positive or negative mold, I can either reuse it to mold plastic reflectors on it or just paint it with something to make it reflective and use it.
I would like to create a negative mold of the ellipse so I can then use it to pour plastic (or other material...I would still like info or suggestions) over it to form new reflectors. So.. if anyone has info on what substance I can use...or can provide some useful links I would be grateful.
Thanks,
Dave
Now remember...for the time being I dont care if I have a ugly beast of a projector...I can make it pretty and small later...What I want to do is use the technique for drawing an elipse around 2 focal points. I will sketch this onto a thin piece of plywood and cut out a flat, eliptical shape. If I can get a bucket of bondo or other material I can set it up so I can rotate the plywood elipse circularly inside the bondo mixture and after a while have a fairly accurate ellipsoidal reflctor cast. Then, depending on if I make a positive or negative mold, I can either reuse it to mold plastic reflectors on it or just paint it with something to make it reflective and use it.
I would like to create a negative mold of the ellipse so I can then use it to pour plastic (or other material...I would still like info or suggestions) over it to form new reflectors. So.. if anyone has info on what substance I can use...or can provide some useful links I would be grateful.
Thanks,
Dave
Dave,
The OHP with 7 K lumens I have is the ELMO HP-A305. Virtually the same thing is for sale now on ebay; see my earlier post.
I think the image was about 60" on a diag. That dimension seemed to be the best balance between brightness and size at the time.
This image was in a dead-dark room, with even the ambient light spilling out of the projector vents competing with the projection.
There's not much hope of getting a trully impressive bright image with the room lights on. Certainly, it can be made better with a high gain screen (expensive) or a high gain rear projection screen (expensive). By expensive I mean a few times the cost of the entire thing just for the screen.
To each his or her own; I wasnt satisfied and went ahead and bought a CRT unit for 1K$. Another person I know sets up an entire room in their home, dedicated to a 640X480 1.4M color panel with a 4K lumen OHP, that they paid me $200 for -
The OHP with 7 K lumens I have is the ELMO HP-A305. Virtually the same thing is for sale now on ebay; see my earlier post.
I think the image was about 60" on a diag. That dimension seemed to be the best balance between brightness and size at the time.
This image was in a dead-dark room, with even the ambient light spilling out of the projector vents competing with the projection.
There's not much hope of getting a trully impressive bright image with the room lights on. Certainly, it can be made better with a high gain screen (expensive) or a high gain rear projection screen (expensive). By expensive I mean a few times the cost of the entire thing just for the screen.
To each his or her own; I wasnt satisfied and went ahead and bought a CRT unit for 1K$. Another person I know sets up an entire room in their home, dedicated to a 640X480 1.4M color panel with a 4K lumen OHP, that they paid me $200 for -
Hmmm, didn't think about that Dave... never bothered to try, and had heard of limited success. Oh well... perhaps if you tried painting the opposite side of the plastic instead or maybe tried a high gloss finish white. *lobbing out ideas*
The lens part...
I dont see how the OHP lens system is much different than a camera.
Say you put a bellows from the lens on down to the stage, so that the only light at the stage has to come through the lens. Then, a flat photographic film plate where the transparency goes...
Presume it's focused on some large drawing on a wall and there's a lens cap so as not to expose the film. In a pitch dark room, pop off the cap and touch off a flash to make a "bulb" exposure, as you might do by holding the shutter open with a film camera.
Whatever drawing this thing was focused on, should now be exposed on the film-plate. Correct?
I dont see how the OHP lens system is much different than a camera.
Say you put a bellows from the lens on down to the stage, so that the only light at the stage has to come through the lens. Then, a flat photographic film plate where the transparency goes...
Presume it's focused on some large drawing on a wall and there's a lens cap so as not to expose the film. In a pitch dark room, pop off the cap and touch off a flash to make a "bulb" exposure, as you might do by holding the shutter open with a film camera.
Whatever drawing this thing was focused on, should now be exposed on the film-plate. Correct?
You are absolutly right jjasniew. But the problem isn't focusing the image. the problem is getting enough of the right kind of light through the lcd all going in the right direction.
Another question for Darth.
You said that brute force is not the way. Isn't that what the big pj companies do with their 10000 lumen lights and itty bitty lcd's?
You said that brute force is not the way. Isn't that what the big pj companies do with their 10000 lumen lights and itty bitty lcd's?
Not from what I've seen, tech head. What the actual projectors are using from what I understand is three seperate mono LCDs for RGB where the source light is being split up, filtered and reassembled. It's a lot easier to work with LCD panels that small because the optics needed at that size are cheaper and easier to work with, plus the LCDs are thinner and specifically designed for this purpose. I could be wrong, but I don't think the actual bulbs in those projectors are much brighter than about 4500 lumens or so for the ultra brights. They can't be too bright or powerful due to obvious heat and size issues. If you can prove me wrong, please do... I don't have one to tear apart, but it seems like the cheapest, easiest route to take and keep a reasonable profit margin. LCD manufacturing can always improve and get cheaper, large size glass lens making will always be expensive. Improve what you can and accept the limitations of the other parts on a size/scale/cost ratio.
I'm simply trying to approach the problem from a logical standpoint. The problems at hand almost all center around light usage, efficiency and distortion. Lumens calculations are simple elementary school math. As long as all of your optics are designed to utilize as much light as possible and keep it focused from one point to the next, you should be rocking. I'm not sure what kind of light loss is on a large LCD panel, but I have a hard time believing it's 90%... I have a feeling it's closer to around 20% if you do things right. If you figure a generous 5-10% loss per lens, only two to three lenses... you should be able to get at least 60% of your light out the end. You have an even 4000 lumens light source properly focused and sized, you should be getting around 2000+ from the projection. That's a daylight usable brightness. As for distortion, removal of that will only come through higher quality lenses.
I'd do this project and be happy with only about a 95% correct geometry... it'd irritate me a bit, but can be forgiven more than a drastically weak, fuzzy, unevenly lit image. Plus, considering the monetary value needed to invest in the proper lenses, once you cured the lighting situation, most of your geometry would improve as well.
The only problem with using OHPs is they're designed to be sloppy and low tech with a lot of wiggle room. You can do it with that kind of setup, but it'd probably be best to replace all the lenses with better quality ones.
jjasniew, the bellows are there to keep ambient light from washing out the image. It would be an excellent idea to encase the entire stretch of projector and light seal all the crucial bits until it came out the end to get the best contrast depth possible, but is again something that shouldn't be worried about until the optics are figured out and optimised.
Something to remember, most all the parts that are being used aren't designed with these purposes in mind. In order to use them to their fullest potential, you have to improve the quality of the parts you have control over to compensate for the ones you don't have control over. The limitations are already known, light works the same no matter where you are in this universe, think about what you're doing and plan a little before diving further in to tweak. Treat the optics like a street system in a downtown city. Yes three lefts do equal a right, but you wind up driving four extra blocks just to do it. You know where you're going, you just need to look at the map to find the shortest route. After all, the shortest route is almost always the cheapest, easiest and most successful.
</cheezy fortune cookie advice>
I'm simply trying to approach the problem from a logical standpoint. The problems at hand almost all center around light usage, efficiency and distortion. Lumens calculations are simple elementary school math. As long as all of your optics are designed to utilize as much light as possible and keep it focused from one point to the next, you should be rocking. I'm not sure what kind of light loss is on a large LCD panel, but I have a hard time believing it's 90%... I have a feeling it's closer to around 20% if you do things right. If you figure a generous 5-10% loss per lens, only two to three lenses... you should be able to get at least 60% of your light out the end. You have an even 4000 lumens light source properly focused and sized, you should be getting around 2000+ from the projection. That's a daylight usable brightness. As for distortion, removal of that will only come through higher quality lenses.
I'd do this project and be happy with only about a 95% correct geometry... it'd irritate me a bit, but can be forgiven more than a drastically weak, fuzzy, unevenly lit image. Plus, considering the monetary value needed to invest in the proper lenses, once you cured the lighting situation, most of your geometry would improve as well.
The only problem with using OHPs is they're designed to be sloppy and low tech with a lot of wiggle room. You can do it with that kind of setup, but it'd probably be best to replace all the lenses with better quality ones.
jjasniew, the bellows are there to keep ambient light from washing out the image. It would be an excellent idea to encase the entire stretch of projector and light seal all the crucial bits until it came out the end to get the best contrast depth possible, but is again something that shouldn't be worried about until the optics are figured out and optimised.
Something to remember, most all the parts that are being used aren't designed with these purposes in mind. In order to use them to their fullest potential, you have to improve the quality of the parts you have control over to compensate for the ones you don't have control over. The limitations are already known, light works the same no matter where you are in this universe, think about what you're doing and plan a little before diving further in to tweak. Treat the optics like a street system in a downtown city. Yes three lefts do equal a right, but you wind up driving four extra blocks just to do it. You know where you're going, you just need to look at the map to find the shortest route. After all, the shortest route is almost always the cheapest, easiest and most successful.
</cheezy fortune cookie advice>
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