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Discussion Starter #1
A method I have been contemplating for some time to increase screen gain is to find a way to selectively disperse projected light. The idea is to disperse light more in the horizontal plane and less in the vertical plane. After all, you don't sit on the ceiling to watch a movie, and most of us don't sit down on the floor.

I tried an interesting experiment today. The basic idea is to machine grooves in the vertical direction that have a semi-circular cross-section. The curvature within each groove will serve to disperse light more in the horizontal plane than in the vertical. The experiment utilized a piece of Plexiglas that I then "machined" grooves into in one particular direction (vertical) by using a wire wheel brush with fine brass wires. This is the same method used to give metals a linear brushed finish. I then used a black Sharpie marker and coated the brushed surface doing my best to get the marker ink down into the grooves.

I then put this small test panel up on the wall and checked how the light was being dispersed from the projector. It definitely works to disperse light more in the horizontal direction than in the vertical direction. I realize this is a very crude attempt but does show what can be done with simple methods. I know that grooves are made but not sure at this point if I was able to achieve a semi-circular cross-section within each groove. Also, in hindsight, it would have been better to use an opaque material rather than Plexiglas. The Sharpie marker helped with that a little but it was still too transparent.

I would like to hear what people think about using this method, perhaps combined with semi-reflective materials (paint or base materials). If anyone has any ideas on how to do this on a full-size screen I would love to hear them. I think that the ultimate goal would be to have individual reflective elements on the screen (sub-pixel size) that would control the reflected light cone in both the horizontal and vertical directions with compression of the light cone mainly in the vertical. Any ideas?
 

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Discussion Starter #4
Could possible find a company that could prep the substrate at a reasonable cost. I will have to do more research on this.
 

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Discussion Starter #5
Another idea...could this possibly be done using a particular fabric weave? It probably would be grooves but would take advantage of the curvature of the fibers (I'm thinking polymer) and the curvature generated by the weave pattern. Any thoughts.
 

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This is an interesting idea, but it sounds like it's a bit complex for the average DIY'er. You might look into existing films as well. One of the problems with this whole idea is that due to the high resolution of our current PJ's and video sources (let alone the coming 4k and better stuff) the lines would have to be VERY close together to not be seen (or cause visual artifacts) during viewing.

Please keep us posted on your research! :T
 

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Discussion Starter #7
Yeah Harp...agreed. The grooves would need to be very small, especially for 4K resolutions. I did some searching for lenticular lenses but it seems the max for large format sheets is 60 lines per inch with would not be adequate. That's part of the reason why I started looking at wire brushes because brushes can be found with wire at 0.003" diameter (76 microns) which would be adequate.
 

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Yeah Harp...agreed. The grooves would need to be very small, especially for 4K resolutions. I did some searching for lenticular lenses but it seems the max for large format sheets is 60 lines per inch with would not be adequate. That's part of the reason why I started looking at wire brushes because brushes can be found with wire at 0.003" diameter (76 microns) which would be adequate.
A wire brush won't give you perfectly straight lines, and getting an even finish might be a problem; but it certainly is worth investigating.
 

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Discussion Starter #9
Harp,

I checked the sample that I created...with the best my own eyes can do, the "grooves" wander somewhat confirming your statement. I will have to find a way to keep the grooves straight. I have an idea that involves a rolling pin and fine gauge wire. It will have to wait until the coming weekend however. Any other ideas from anyone would be welcomed.
 

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Harp,

I checked the sample that I created...with the best my own eyes can do, the "grooves" wander somewhat confirming your statement. I will have to find a way to keep the grooves straight. I have an idea that involves a rolling pin and fine gauge wire. It will have to wait until the coming weekend however. Any other ideas from anyone would be welcomed.
While I'm just talking off the top of my head here I think there is a good chance that the vertical grooves don't really need to be totally straight or run the full length of the screen to achieve what you are after. :dontknow:
 

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Discussion Starter #11
I think you are essentially correct. I think that the most critical parameter is getting the curvature of the groove that you need to evenly disperse the reflected light to avoid variation in brightness as you move through the horizontal cone.
 

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Discussion Starter #12
Tried a couple of experiments today. Rolled a neutral gray onto a flat substrate and then tried to roll a coiled tension spring through the paint to form semi-circular grooves. Didn't work too well as the spring would not roll evenly through the paint. The backside of the coil would also pick up the paint as it came out of the paint.

Also tried to heat a piece of plexiglass and then rolled the tension spring into the hot surface. I was able to make grooves but could not apply pressure equally enough to make the grooves consistent. Like you guys said, this probably isn't a DIY application that will be easy. Still going to think of some ideas to make the grooves consistent in a substrate. Thinking of using a really solid mandrel wrapped with fine gauge wire then rolling into a pliable substrate. Again probably not DIY.
 

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We learn as much, or more, from our mistakes as we do from our successes. ;)

If it becomes possible to control the image dispersal as you are trying to do via even a difficult DIY process, people willing to get their hands dirty can save HUGE amounts of money over engineered screens like the S.I. Black Diamond and get even BETTER results!

Thanks for sharing your experiences with us! :T
 

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Discussion Starter #14 (Edited)
Made a bit of progress using aluminum foil.

I put down a piece of cloth on a hard flat surface, then carefully laid the aluminum foil on top of the fabric. Then I used the coiled tension spring (template) to drag across the surface of the foil multiple times. I did this on the shiny side of the foil. By carefully dragging the spring across the foil multiple times, I was able to press fairly nice grooves into it. The foil tends to curl up a bit. I then carefully flipped over the foil and painted the dull side with a Valspar satin neutral gray (Icon Grey 00NN 31/000 N6.25) using a touchup 1/4" nap roller being careful not to mash the texture. Spraying may be better.

Now, the sample is very small...only about 4" x 4" but the results were interesting. It was apparent that the grooves need to be thinner...these were approximately 1mm wide, about the same width as a pixel. Before I put any pictures up, I still want to do some more experimentation with thinner wire and work on keeping the foil flat. Perhaps a thicker foil. I need to get my hands on my kids camera so I can take decent pictures. All I have is my phone cam.
 

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Discussion Starter #15
Although it was interesting to see what this idea would do, the more I think about it, the less I believe it can accomplish what we are looking for. The horizontal curvature also serves to disperse any ambient light which is a negative. Curvature in only one direction still doesn't allow the use of higher sheen paints as it will tend to form a "hot line" that runs across the screen. The only way to solve the problem is to also give the texture a slight curvature in the vertical direction or actually curve the entire screen in the vertical direction. Any thoughts?
 

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Although it was interesting to see what this idea would do, the more I think about it, the less I believe it can accomplish what we are looking for. The horizontal curvature also serves to disperse any ambient light which is a negative. Curvature in only one direction still doesn't allow the use of higher sheen paints as it will tend to form a "hot line" that runs across the screen. The only way to solve the problem is to also give the texture a slight curvature in the vertical direction or actually curve the entire screen in the vertical direction. Any thoughts?
Not really. This was going to be a difficult project from the get-go. There is a reason that the commercial engineered screens cost so much besides just greed. Another problem is that as image resolution of PJ's keeps getting finer and finer the "lenses" of engineered screens are going to have to get smaller and smaller and there will be a point where they simply can't do that and will cause negative visual attributes.
 

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Discussion Starter #17 (Edited)
Harp, Your comment and a recent experience standing next to a panel of brushed stainless steel got me thinking about my pieces of aluminum. I noticed my reflection in the brushed SS panel showed a dispersion of light perpendicular to the brushing. This confirms my original thoughts. I decided to take a piece of aluminum foil to work were I have access to a light microscope. I was curious look at the micro-texture and I found a very interesting texture on the dull side.

Here is a 500X photo of the dull side of a piece of standard Reynolds Wrap foil:



Here is the same area using Differential Interference Contrast (DIC, shows better shadow detail):



I didn't expect the texture that was revealed. The features that run perpendicular to the foil rolling direction will likely give more dispersion of light in the rolling direction (horizontal) than in the vertical direction. I need to do some further testing, but we may have a way to get past the ever finer "lenses" and get some selective dispersion. Also need to think about how to topcoat the foil as it hot spots when naked.
 

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Discussion Starter #18
Tried to take a look at the dull side of aluminum under projected light this morning. Standard foil is just too difficult to work with and keep perfectly flat without causing bends and folds in the surface. Although my results are subjective, it does appear that the texture provides a small amount of selective diffusion. I don't think it's enough to do what I want. I tried to find foil in 48" widths and only found a few sources. Wouldn't be easy to obtain, and probably harder for anything above 48" widths.

Moving on....(for now)...

Decided to pick up a piece of glossy whiteboard from Lowes and some 320 grit sandpaper + sanding block. I taped off one half of the board to keep it glossy. On the other half, I used the sand paper in one direction only (vertical with respect to the screen) making long complete top-to-bottom, or bottom-to-top strokes. This essentially creates a very fine brushed surface. I used the rest of the Icon Grey satin sample that I had and painted both sanded and glossy sides after a cleaning of all the sanding dust. Painted with a 1/4" nap 4" roller. Sample is drying and will test in a little while.
 

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Discussion Starter #19
Well, simply using sandpaper didn't work. The paint I used is too opaque, not letting light get to the scratches to work on dispersing light the way I want. I will have to try again. 320 grit paper may have been too fine as well. 320 grit corresponds to 33 microns. Maybe something a bit more coarse would be better. The quest continues.
 

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Very interesting Jason. Probably the best way to initially make a paint more translucent would be to add Behr Faux Glaze to it.
 
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