I now have a half working projector together (OHP & Goodmans portable dvd player/screen)
I wish to make a screen as my wall is a bit mucky and im sure it blurs the light a little.
I have been reading threads for days now with 100's of sujestions but what I cant seem to find information on is WHAT makes whatever your using a good screen. What should I look for in the matirial I use, Its all good telling me that the ikea blind you use works very well, but i need to know WHY it works well.
Please help me as I dont wish to make a poor quality screen
I wish to make a screen as my wall is a bit mucky and im sure it blurs the light a little.
I have been reading threads for days now with 100's of sujestions but what I cant seem to find information on is WHAT makes whatever your using a good screen. What should I look for in the matirial I use, Its all good telling me that the ikea blind you use works very well, but i need to know WHY it works well.
Please help me as I dont wish to make a poor quality screen
This "screen" from Ikea works well, because you can roll it out when not in use. Other than that it's not a bit better, then a wall painted with good, white matt paint. And this "screeen" soon will become weavy. If you can paint the wall, I would do it (as I actually did). Just choose really white, good paint (Flugger, Dulux, etc. good brands, not just cheap "white ceiling paint", and ask for a pure white one)
Regards
Regards
I have read many posts saying exactly the same thing. its not what i need
This thread is here for people to explain WHY I should use extra white paint or WHY blackout cloth or whatever.
I need to know WHY they are good or bad.
What has X got over Y that makes it better ???
So to ask again CLEARLY........
What is it that makes a good screen and WHY. what is it that makes the picture brighter & clearer.
I dont want lists of things you "can" use for a screen, i want to know WHAT MAKES A GOOD SCREEN AND WHY
This thread is here for people to explain WHY I should use extra white paint or WHY blackout cloth or whatever.
I need to know WHY they are good or bad.
What has X got over Y that makes it better ???
So to ask again CLEARLY........
What is it that makes a good screen and WHY. what is it that makes the picture brighter & clearer.
I dont want lists of things you "can" use for a screen, i want to know WHAT MAKES A GOOD SCREEN AND WHY
That depends upon your application!
Very generally, the more 'directional' the screen surface, the brighter the image, but the narrower the viewing angle.
I don't really know why people mess around with 'substitute' materials (except for the sake of experimenting), when proper commercial material is available at a reasonable price. If you want an image up to 60" square, you may well be able to obtain a second-hand screen for nothing.
My preference is for the beaded type, as it has high gain, albeit a fairly narrow viewing angle - fine in my setup, but your mileage may vary.
Very generally, the more 'directional' the screen surface, the brighter the image, but the narrower the viewing angle.
I don't really know why people mess around with 'substitute' materials (except for the sake of experimenting), when proper commercial material is available at a reasonable price. If you want an image up to 60" square, you may well be able to obtain a second-hand screen for nothing.
My preference is for the beaded type, as it has high gain, albeit a fairly narrow viewing angle - fine in my setup, but your mileage may vary.
GAIN ???
Reading more posts i come across the word GAIN,
What does this mean.
And how can i tell what "GAIN" my materal or paint has ??
Reading more posts i come across the word GAIN,
What does this mean.
And how can i tell what "GAIN" my materal or paint has ??
It's a misnomer really - a screen can't achieve any real gain! It refers to the proportion of incident light which is reflected towards the viewer - its efficiency, if you like.
Commercial screen materials include the gain in their specification. In the case of other materials, it's a case of measuring or comparing.
Commercial screen materials include the gain in their specification. In the case of other materials, it's a case of measuring or comparing.
Actually, thinking about my last reply, I suppose actual gain IS theoreically possible. If a fluorescent finish were used in combination with a source rich in UV to excite it, it would actually 'shine'! (The technique was used by a number of 'old masters' to make their paintings luminous).
Anyone tried it (I know the trouble with UV and LCDs would't help)?
Anyone tried it (I know the trouble with UV and LCDs would't help)?
Everyone keeps talking about blackout cloth. Jo Ann Fabrics has it cheap as long as you want in 1 dimension, but its only 54" tall. People talk about stretching it out to make a smooth screen, but surely it won't stretch out to double its original size. The largest you should be able to get is like 1.333333 times that correct? Around 70" for 4:3 screen.
Where can one buy blackout cloth which is taller?
Where can one buy blackout cloth which is taller?
gain = mostly hogwash!
Lots of discussion threads about various screen materials at:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=23
But beware: Some very exotic screens and materials (ie. painted mirrors, etc.) are touted as having "high gain", relative to a flat white surface. Some curved metallic screen makers claim a gain of 8 or higher!
I did some experiments with various paints, etc. and I have a real LUX meter. I found that my LUX meter reads about 100 LUX facing the projector (against the screen surface), and reads about 70 LUX facing the screen from 1 foot away. So flat white paint reflects about 70% of the projected light with perfect viewing from all angles. You could only get about a 30% improvement with a perfect mirror surface. So how can you get 8 times more light? 🙄
One of the very best surfaces I found was unpainted wallboard mud skimmed over the wall surface (to get rid of the texture) and then sanded flat and smooth.
Lots of discussion threads about various screen materials at:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=23
But beware: Some very exotic screens and materials (ie. painted mirrors, etc.) are touted as having "high gain", relative to a flat white surface. Some curved metallic screen makers claim a gain of 8 or higher!
I did some experiments with various paints, etc. and I have a real LUX meter. I found that my LUX meter reads about 100 LUX facing the projector (against the screen surface), and reads about 70 LUX facing the screen from 1 foot away. So flat white paint reflects about 70% of the projected light with perfect viewing from all angles. You could only get about a 30% improvement with a perfect mirror surface. So how can you get 8 times more light? 🙄
One of the very best surfaces I found was unpainted wallboard mud skimmed over the wall surface (to get rid of the texture) and then sanded flat and smooth.
From a mechanical perspective...
Another thing to consider when it comes to screens is keystoning...
If you have a keystone issue, you can correct some/all of the keystone effect if you have a screen that you can tilt.
Im currently projecting on a white wall... but my testbed projector is straight across from the wall... when I build the final projector it may not be perfectly square with the wall so Id have some keystoning, and would rather tilt the screen up or down a bit to adjust rather than messing with the fresnels.
From an image quality perspective...
The screen needs to be matched to the projection system...
You might find this helpful:
http://www.dalite.com/education/guide.php
Another thing to consider when it comes to screens is keystoning...
If you have a keystone issue, you can correct some/all of the keystone effect if you have a screen that you can tilt.
Im currently projecting on a white wall... but my testbed projector is straight across from the wall... when I build the final projector it may not be perfectly square with the wall so Id have some keystoning, and would rather tilt the screen up or down a bit to adjust rather than messing with the fresnels.
From an image quality perspective...
The screen needs to be matched to the projection system...
You might find this helpful:
http://www.dalite.com/education/guide.php
I agree with Guy. Most gain is refering to their wallet.
Get a good white paint or a standard rollup screen.
What makes white paint white? Some are whiter than others. The difference is the quatity of pigment particles in the paint base. Cheap paint is cheap becasue its thin. White is made by titanium dioxide pigment. An example of the best whites is the Behr ultra pure white. Its at home depot. They use more pigments. The same process for making a colored paint can get you a better white. Ask the paint store guy to put 2 shots of titanium in their white.
A semi gloss has more "gain" than a eggshell finish which has more than a flat finish. As you get more "gain" you get more glare. This can make a real hotspot on your screen. Go with flat or eggshell.
I use a rollup in front of the TV. Pulling down a screen for movie time adds to the theatre feel somehow.
Get a good white paint or a standard rollup screen.
What makes white paint white? Some are whiter than others. The difference is the quatity of pigment particles in the paint base. Cheap paint is cheap becasue its thin. White is made by titanium dioxide pigment. An example of the best whites is the Behr ultra pure white. Its at home depot. They use more pigments. The same process for making a colored paint can get you a better white. Ask the paint store guy to put 2 shots of titanium in their white.
A semi gloss has more "gain" than a eggshell finish which has more than a flat finish. As you get more "gain" you get more glare. This can make a real hotspot on your screen. Go with flat or eggshell.
I use a rollup in front of the TV. Pulling down a screen for movie time adds to the theatre feel somehow.
"super" screens
There are all sorts of experiments and commercial products that all try to improve screen brightness and contrast over something like flat white paint. This is based on the very wide dispersion of light reflected by a flat white screen. Each pixel sends light in all directions over a solid 180 degree field. If a screen material can direct all the reflected light to a narrower field, then it will be brighter.
An ideal screen would consist of one tiny mirror per pixel that would direct all the light falling on that pixel to the viewer. Anyone else in the room would see a black screen! There is actually a material that can almost do that: retroreflective glass beads. These are used on road markers, etc. to direct light back in exactly the direction it came from. So in our case, the viewer would have to have his face right beside the lens! Not so useful!
"super high gain" materials like aluminum paint reflect at such narrow angles that you see a hot spot where the angle of incidence is equal to the angle of reflection, like looking at a light bulb in a mirror. They use a curved screen to spread the hot spot over the whole image. These can be very bright, but the viewing angle is also very narrow. Good for a single-guy, not so great if you have a guest!
Some people swear by a mirror or aluminum paint surface coated with a translucent layer of white paint. The idea here is that some light leaks all the way through the white layer, gets reflected off the mirror, and then "lights up" the white layer from underneath. No science behind this, just some enthusiastic fans. One big problem with this is that it requires expert painting technique (ie. like custom auto finishing) to get it right.
My screen is painted on my wall. I filled in the texture with wallboard mud, sanded it smooth, and sealed it with white vinyl primer designed for that. Then I applied a couple of coats of Behr Ultra Pure White flat exterior, wet sanding after each coat dried. Then a couple of coats of Behr White Opalescent faux finish. Then a couple of coats of Behr Matte Clear Polyurethane. It is pretty bright with no hot spots, but not perfect. I am not that great a painter, so the reflectivity of the Opalescent layer is somewhat streaked. It is very difficult to get even, since it is transparent and the effect is cumulative as you recoat.
I actually made about 10 different screen formula test squares before I started, and then I tested it along the way, and I will confess that the sanded wallboard mud, the vinyl sealer, and the Ultra Pure White flat layers all looked very good to me. If you have enough light from your projector, I would recommend any of these. The UPW is probably the strongest surface, in terms of wear and cleaning.
There are all sorts of experiments and commercial products that all try to improve screen brightness and contrast over something like flat white paint. This is based on the very wide dispersion of light reflected by a flat white screen. Each pixel sends light in all directions over a solid 180 degree field. If a screen material can direct all the reflected light to a narrower field, then it will be brighter.
An ideal screen would consist of one tiny mirror per pixel that would direct all the light falling on that pixel to the viewer. Anyone else in the room would see a black screen! There is actually a material that can almost do that: retroreflective glass beads. These are used on road markers, etc. to direct light back in exactly the direction it came from. So in our case, the viewer would have to have his face right beside the lens! Not so useful!
"super high gain" materials like aluminum paint reflect at such narrow angles that you see a hot spot where the angle of incidence is equal to the angle of reflection, like looking at a light bulb in a mirror. They use a curved screen to spread the hot spot over the whole image. These can be very bright, but the viewing angle is also very narrow. Good for a single-guy, not so great if you have a guest!
Some people swear by a mirror or aluminum paint surface coated with a translucent layer of white paint. The idea here is that some light leaks all the way through the white layer, gets reflected off the mirror, and then "lights up" the white layer from underneath. No science behind this, just some enthusiastic fans. One big problem with this is that it requires expert painting technique (ie. like custom auto finishing) to get it right.
My screen is painted on my wall. I filled in the texture with wallboard mud, sanded it smooth, and sealed it with white vinyl primer designed for that. Then I applied a couple of coats of Behr Ultra Pure White flat exterior, wet sanding after each coat dried. Then a couple of coats of Behr White Opalescent faux finish. Then a couple of coats of Behr Matte Clear Polyurethane. It is pretty bright with no hot spots, but not perfect. I am not that great a painter, so the reflectivity of the Opalescent layer is somewhat streaked. It is very difficult to get even, since it is transparent and the effect is cumulative as you recoat.
I actually made about 10 different screen formula test squares before I started, and then I tested it along the way, and I will confess that the sanded wallboard mud, the vinyl sealer, and the Ultra Pure White flat layers all looked very good to me. If you have enough light from your projector, I would recommend any of these. The UPW is probably the strongest surface, in terms of wear and cleaning.
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