Originally Posted by benven
Thanks bud. But, I'm having a hard time understanding what you stated. The light will bounce back from the mirror and hit the back of the paint layer. The paint layer on the glass will have a gloss lustre to it. I can sorta rationalize this in my brain. So in stating that how does RS MAxx or BF react on the glass. I would assume much in the same way. And if they do, viewing cone would be affected.
Anyway, I guess what you are trying to tell me is that even white matte paint layer would not diffuse the light enough. Therefore, any paint layer, thin enough, would have the same result?
I think we are pretty much on the same page here. First the light has to pass thru something paint or films etc. and become diffused in two direction some being reflected back instantly as in a normal screen some being diffused and sent into the mirror on passing thru the glass of the mirror being as how the glass is fairly thin the light cant be dispersed to far off target before striking the silver the angle it strikes the silver will be the opposite of the angle it leaves the silver. Now the return trip starts. Back thru the glass and this time it contacts the back side of the paint finish. This finish will not be governed by the flattening agents in the paint but the smoothness of the glass the paint dried to. And glass is very smooth in order to be transparent.
What tiddler was saying is that it could possibly act as another partial mirror again and thus the bouncing back and forth within the glass. That's one way light can be lost another is what happens in fiber optics. In thin layers of glass light that comes in on a very slight angle can never exit the fiber / sheet the light will take a zig zag path down the length and exit on the other end every material has a different angle that this takes place at. So in theory if some of the light diffused the first time into the glass at a slight enough angle it would likewise be trapped. All this bouncing around will also soften the focus if the mirror glass is two thick and could be the reason we hear of a halo or plasma glow. (don't really know)
The idea I had of etching / sandblasting the front face would take the place of the first layer diffusing paint. And along with doing that it would make the second light path reflected out an equally textured light scattering path. And that equates to viewing angle / cone. But as viewing cone widens gain has to drop. There is only so much light to go around the wider you spread it the less there is for each viewer to see. The screen cant make light so no mater what kind of screen you have it's a matter of what you do with the lumens you have. Ideally you adjust the viewing cone to match the seating and then make a screen that has a high efficiency. And by that I'm saying a screen that converts the most amount of light it can to watch able image and returns it to the viewing area. Less wasted light is another way to state it. Gray screens / trapped light / light passing thru a screen are all wasters of light. Thus lowering the overall efficiency of the system.
I took a totally different approach to the problem. Somewhat by design and somewhat by luck. But realizing luck when you see can be a form of science. First off my projector it delivers close to two times the light I would normally need for the image size I'm shooting. Second my screen material is canvas with a texture that acts as a natural reflective diffuser when painted. Then I went down the neutral gray road and found the shade that killed enough of the lumens to get me in a good ft Lambert range and in doing so pushed the perceived CR of the dark end. At that point I was happy but lacking hot whites and pb maxx answered my request into adding poly's to gain sheen to boost gain. My experiments lead me to a poly level I now know is way to high for a smooth screen. (see tiddler's testing thread of poly) the reason I could go so high of a level I now believe is because of the texture / diffusion of the canvas without hot spotting.
I had at this point an inefficient screen still that because of the high starting lumens produced a very bright image with great CR and excellent blacks.
I had the chance last week to test my screen against a Da-lite sample of there silver gray high contrast material. The first thing I noticed was the sample had a textured surface and a sheen similar to mine only a slightly darker gray / silver in room light than mine and mine the texture was more pronounced. They were so close in side by side testing during a movie I almost forgot there was a sample across the screen.
I know no light makes it thru my screen and the first 3 coats of paint had no poly so I'm assuming the image is taking place against that top coat of the base and in the two coats of the poly paint I top coated with. Because it's possibly going thru some of the paint a slight depth and coming back out can I call this light fusion? I don't know about that.
Would someone with a less bright projector be able to get away with just neutral gray poly screen? I don't know about that ether. Tiddlers test show a fair improvement side by side between gray poly and gray poly metallic and he did a much better job of matching the gray levels as compared to first comparison using SS as the gray poly. But I have to point out even the gray poly he used in the above test started at a darker value and because of his flat substrate the poly level was lower, thus a wider viewing cone than the gray, poly, metallic. It was a fair test in all as are all his tests. I'm not quite ready yet to throw in the neutral gray poly towel. But I am considering posting the above thought process concerning extra lumens into my thread as a edit.
Proponents of metallic LF and all the rest will point out to me that with them combined with my lumens I even have more to gain. I don't know about that ether. MM just did a contract for a screen using these latest advancements for a XR10X projector and I have been following that story closely. The screen he did was a good 30% smaller than mine and with the lumen output I was expecting a screen that looked almost black under room lighting. I figured with the efficiency of the better screen the base shade could be dropped more and super high black CR could be had along with amazing ambient light rejection. So far only a few pictures were posted and I was surprised the mix he used was close in room lit gray to mine. When more screen shots become available maybe the towel will fly in the ring. We'll have to wait and see.