Hi Hometheatershack! I got interested in this experiment when I stumbled upon this thread. According to me, this is a good idea in theory. A higher quality glass mirror reflects nearly 100% of the light hitting it, in my opinion you wouldn't find anything with more gain than a mirror, right? If you used a mirror as a projection screen you would obviously not see anything but a bright flare from the projector lens, but if we applied a ultra matte coating, wouldn't we get a very high gain screen with no color artefacts? Maybe hot spotting would be a potencial problem, but has anyone heard of someone trying this? I havent seen the Vutec UHG screen, but guessing it must have been some sort of matte semi translucent fabric or coating on top of the reflective surface.I have always believed that a modified version of the Vutec UHG screen could achieve the same thing as BD. Basically, Vutec's curved screen was a translucent material over aluminized mylar or mirror. It gave a gain of around 5 I think. I think if you put a dark translucent material or coating over the mylar you might be able to reduce the gain.
Hi Partik, welcome to HTS! :wave:Hi Hometheatershack! I got interested in this experiment when I stumbled upon this thread. According to me, this is a good idea in theory. A higher quality glass mirror reflects nearly 100% of the light hitting it, in my opinion you wouldn't find anything with more gain than a mirror, right? If you used a mirror as a projection screen you would obviously not see anything but a bright flare from the projector lens, but if we applied a ultra matte coating, wouldn't we get a very high gain screen with no color artefacts? Maybe hot spotting would be a potencial problem, but has anyone heard of someone trying this? I havent seen the Vutec UHG screen, but guessing it must have been some sort of matte semi translucent fabric or coating on top of the reflective surface.
As Ericglo states, putting a dark translucent material or coating on top of a mirror or mirror film ex. mylar may give us a dark screen with a fairly high gain? Mirrors are expensive and hard to come by in these sizes we're talking about, so, as Ericglo said, mylar might be a good option, even though it reflect only 60-80% of the light hitting it.
I'm thinking, MDF-board painted black > mirror film > translucent dark sun film > ultra matte coating.
Would love to have your comments on this idea!
Thanks for your reply Harpmaker!Hi Partik, welcome to HTS! :wave:
Simply put, there is no way to make a DIY Black Diamond-type screen. If the processes that make such a critter aren't machine-controlled you will almost certainly get too many imperfections that will show up during use. Even the real BD screens are disliked by many people for having negative visual artifacts such as sparkle or hot spotting. Eric's point was in trying to make a curved screen with similar attributes as a BD. The curve of the screen would help mitigate the hot spotting that will occur if a flat screen is used.
You may find links on the web to another DIY screen forum that purports to have a paint formula that will, in their words "meet or beat" the performance of a BD screen; but don't believe it. The claims of performance for that forums screen mixes are offered without proof of performance, and the few we have tested fell short of the promised performance.
The forum I read about the Swedish Black Screen on is quite famous for painting mirrors on their DIY Screens forum. Unfortunately, they totally ignore the laws of reflective physics there and those screens don't work all that well.Thanks for your reply Harpmaker!
I've read a lot about DIY diamond screens on the web, just as you said, it appears there are no way such a DIY screen could be built to a low cost. A swedish guy from the swedish forum "minhembio.com" has come up with a recipe named Black Screen™. (Search for "Black Screen from Sweden") I've only judged from the pictures I've seen but I must say I was impressed when he compared it side by side with the BD, but on the other hand, the processes of making the screen is very expensive but also secret.
Just curious to know, even if we won't be able to clone a BD, could we make a high gain screen with the help of a super reflective material such as a mirror? Still curious to find out what would happen if you put a matte coating on top of a mirror (I'll try that when I get back from my vacation). Trying to curve a mirror would most likely end up with seven years of bad luck, so I would bet hot spotting would be the greatest problem to deal with.
Have anyone heard of a DIY screen involving a mirror?
Well, lets face it, this is complicated stuff :doh: I appreciate your comments on my wild ideas though! I'm really glad I've found this forum anyway, I have no plan of giving up trying to find the ultimate DIY screen Unfortunately (for now) I have white walls and white ceiling, and the sad part is, there's nothing I can do about it (of course, technically I can, could paint them black, use black curtains etc. but as the only home theater enthusiast at home, these arguments are tough to win). Light bounces out from the screen, on to the white walls / ceiling and then back in to the projected image, destroying the blacks. A simple grey screen didn't give me what I was looking for, turned the whole image "flat" even though blacks got better. Would like to have a HC screen, reflecting the light back at the audience, not to the walls or ceiling.The forum I read about the Swedish Black Screen on is quite famous for painting mirrors on their DIY Screens forum. Unfortunately, they totally ignore the laws of reflective physics there and those screens don't work all that well.
If you are not very careful using a mirror as a screen substrate you will end up blurring the projected image to the point of visibly softening the image, even if a first-surface mirror is used. Think in terms of the path of the light rays striking the screen. Any diffusive front coating will start blurring the image as the rays of the image go through the coating; these rays will continue to diverge even after being reflected from the mirror and will be diffused again on passing through the coating on their way out. Any coatings used on the mirror would have to be very thin to mitigate this effect.
High gain dark screens have problems in a number of areas; they are known for hot spotting, image blurring, color changing of the image, and costing a fortune. They are niche products that are only worth these disadvantages in very special situations.
I don't mean to crush your spirit of invention, but please don't think you can break the laws of physics. Good luck on your endeavors! :T
High mechman! I agree with you, a first surface mirror is a must, thinking of what harpmaker said, you can't escape or change the laws of physics! Can't think of anything else than glass or acrylic glass to mount the mylar on and that would also be a significant cost. A company here in Sweden sells a reflective film, as mylar, that shrinks when heated. They recommend to stick the film on to a frame and then heat it up! That would cause the film to shrink a tension it self. Result? A totally flat first surface mirror to a reasonably low cost.A mirror will not work well at all. Mylar, on the other hand, might. I've had some mylar for a long time but I've never done anything with it. It would be a real pain trying to get that attached to a substrate flat without bubbles. But it takes the gap between the mirror and the glass surface out of the equation.
It's hard to see exactly how bright the room is from photos but I can tell you that the room is well lit from 3 directions. A good portion of the light is sunlight coming in from the large double window facing the screen. The projector is in front of the window and the test was done in the middle of the afternoon.
Other than being outside, it doesn't get much brighter than this. You can see how the "high contrast grey" screen from screen goo struggles to give a visible image. The black screen is watchable.
On the translucent paint, yes it was very hard to get an evenly painted surface using a roller. The best I achieved was using a screen printing roller which is solid plastic instead of soft foam etc. Even then, it only gave a good image when you stand back. In the end, I bought a sprayer from home depot for $80 which did the job easily and quickly. I feel like my bones are still vibrating from the noise of it.
It is a shame I had to reduce the quality of the image to upload them because what you can't see is how sharp the picture is. I wanted to see if it is possible to create a version of black screen technology at home and I concluded that it is. I also believe there are better ways to do it than this now I understand the principle.
I am currently experimenting successfully with a similar screen type which uses a charcoal colored rear projection fabric with a solid reflective coating on the back to turn it into a front projection surface. I want the front surface to be fabric instead of paint to make sure it is smooth. All of the high priced solutions advertise a "multi layered" technology although they tend to be somewhat evasive on further details. I have seen dozens of patents described for projection screens and very few of them from screen innovations and DNP. They are all there for anyone to read and it is worth doing a little research to understand the science when designing your own. You don't have to worry about patents for your own mix. The Sony Dynaclear uses a dichroic coating to make it "selectively reflective". Essentially a multi layered coating that only reflects red, green and blue light from the projector and nothing else. Who says it is impossible to make your own dichroic coating or to get a company to make one for you?
I think this is where home solutions fall down sometimes. Mixing paint doesn't always give you the properties of both colors. For example, red pigment is great at reflecting red light, but it also absorbs green and blue. Mix red, green and blue paint and you will probably absorb all of them and get a very dull image. That is why you sometimes don't achieve the increase in gain you might expect from mixing reflective paint like aluminum into your mix. The challenge is finding something to enhance reflectivity where you want it and not absorbing colors you do.
Mixing water based aluminum paint with white or beige gives me a grey paint. In theory, this is meant to have a much higher gain than just using a ready mixed neutral grey which is made from black and white pigment. The trouble is that I couldn't swear that the difference in gain is that significant. I'm sure others have had better results than me but there has to be a reason why aluminum paint isn't generally used in high end screens.
I bought some Speedball aluminum ink which is used for screen printing and some newton and windsor aluminum ink. Both will mix with acrylic or water based paints. I found a significantly greater improvement in gain than I was able to with Auto-air water based aluminum paint. also, with the speedball roller, I found it a lot easier to get a smooth and consistent finish. I couldn't tell you why but I have a feeling it is something to do with the greater saturation you get with ink over paint. Mixing the silver ink into white or beige paint and the end result still has a metallic look instead of turning to light grey. You still get a watchable screen without hotspots, only much brighter. Silver ink can even make black paint reflective enough, to use with the right projector, without turning the paint light grey. I am experimenting with this right now.
I am a fan of black widow mix generally. I added some aluminum ink to my black widow paint mix and it closed some of the gap with more expensive high gain screens. I have tried a lot of these commercial offerings btw and I am almost always disappointed. None of the big players have a right to claim "innovation" in this space in my opinion. The elusive commercial screen that works well in all conditions, with all projectors and at a price that doesn't singe our nose hairs, has not been created yet. DNP charge $25K for their flagship screen. It may be great, it is a shame that hardly anyone will ever know so it is irrelevant.
I will try and upload a video link to Youtube to show the black screen in a way that shows how bright the room was and where the light was coming from.
You have some great ideas Rob, thanks for sharing!Patrik
I am interested in what you were saying about frosted glass. Perhaps I can learn from your experience and save myself some time and cost.
Was the surface of the frosted glass you used smooth or rough? Did you try it with a smooth film over the frosted layer? Also, did you try it with a black layer behind the glass?
I ask because I found that taking some anti glare plaxiglass and painting the back with aluminum paint, gives you a watchable projection surface, even if the aluminum paint is not evenly spread.
People always warn against mylar because it has a mirror-like finish but I have wondered how it would respond with a thing translucent light diffusing layer on top. It is designed to reflect light. I have experimented with one way mirror window tint film. It doesn't do much for reflectivity once you add paint but it does give you a really smooth surface to paint on which helps the finished layer.
There are tons of window tint films on ebay specifically designed to reflect, absorb, or transmit light in a very specific way. The right combination could probably make a good multi layered screen.
I want to try it with a tinted layer, reflective layer and then use glass bead (powder consistency) as the front diffusing layer for a retro reflective screen experiment.