OK, pics of results. Before I post some, it is worth mentioning that this mix is not jet black and is not intended to be. It is far darker than any commercial grey mix available though and much darker than diy mixes like black widow. I will also say that in performance, it is not as good as the fabric black screen but it is cheaper to make and if you are not comparing it to the fabric option in a side by side, it gives very pleasing results. I would estimate the gain to be around 1 which is fine for most modern projectors. The gain can be increased by making it slightly lighter or, making it thinner and adding a layer of aluminum ink below it.
In the pic above, the black paint mix is at the top of the foam board and you can see some of the white paint / aluminum mix at the bottom. I should also state that this test is more "real world" than other tests I have done. The lights are on but the room is not massively bright. There is little sunlight and most of the brightness is from the room lights. This would be typically living room brightness that is representative of how I would watch. I am not going out of my way to shine direct sunlight on the samples. I am using my Projectiondesign F32 1080 set to single lamp mode in eco setting. It is also set to movie mode so I am probably putting out 1500 - 2000 lumens. I tested the mix with a 700 lumen device too and it worked fine. Testing with this projector has been harder than normal because it is so good, it puts out a great image on most screens. It's like testing how much faster I get around a track with an engine mod in a Ferrari - it is easier to see the improvement caused by a screen if you don't start with an amazing image. I can still see differences, it just makes it harder to capture the improvement in photos.... For the test, I found the best images came from shots that didn't have screens with multiple different levels of brightness.
For example, the following pic shows the netflix red logo on my fabric black screen (top) and the painted black screen (bottom). The paint option looks dull in comparison and if I stopped the test there, I would have drawn the wrong conclusion.
Here is a pick of the netflix red logo close up, only showing the black painted surface. Without a brighter comparison screen, the colors look vibrant with good contrast and pure whites:
Here is another pic to illustrate the testing problem. It shows the white test patch with the fabric black screen behind it. For the fabric screen, the shot is off-axis (the black screen is brightest from in front of it like all retro-reflective surfaces). The image makes it look like the white paint is bright with vibrant colors while the black screen is dull.
This really isn't the case btw.
Here is a pic from a more central point:
The pic above is a little more representative of what I saw in person but still misleading. Here is a similar shot showing all 3 surfaces:
In the pic above, the black paint is on the right, the white paint is on the left and the fabric black screen is in the background. The black paint, again, looks dull in comparison to the other 2 as it has a lower gain. If I take a shot only showing the black paint surface though, our eyes adjust and it looks good:
To further complicate things, the part of the screen occupied by the black painted surface, is darker than the area above it. As expected, scenes with light colors are enhanced by the white screen while scenes with dark areas are unwatchable with the lights on. The main problem with the comparison though, is the tricks our eyes play on us when there is a brighter surface to compare it to. This speaks to flaws in side by side comparisons generally, it was just less noticable with the fabric black screen which has both a decent gain and high level of contrast. The next pics I am going to show, only have the black painted surface because, it looks really good on it's own. While not as good as the fabric option, it is far better overall than the white paint. With lights on, there is no comparison. The gap would be even larger if I was using a lesser projector. The F32 is bright enough to put out a good image with the lights on, even with a white screen. If you have a less powerful device, the black screens improved performance will be far more noticeable as no white screen looks good with the lights on with home theater projectors.
Look at the Louis CK icon in the pic above. The colors look good. If I try and take a photo including the brighter fabric screen behind it, my eyes start to play tricks again and the same image, with the same projector, taken using the same camera, now looks dark:
The key point is, the paint works well, it is just hard to take comparative photos to show you what I'm seeing. There is also the point about calibrating the image to the screen. adjusting the projector brightness a few points can eliminate any difference in perceived brightness.
Above, Spy kids icon with half black, half white. Below, Just using the black paint surface:
Scenes with black backgrounds have the reverse issue:
With black backgrounds, the black painted screen looks far better than a white screen with the lights on. This is predictable but the difference isn't as great as the pic suggests. While the white screen does look washed out without blacks when the lights are on, the side by side comparison makes the white surface look worse. On it's own, the difference is 50% less although still obvious.
Above, the black border on a 2.40:1 movie. The black painted surface outperforms the white surface as predicted.
The pic above shows a black image with the lights off. Half is on the white paint, the other is on the black paint. Even with no room lights, the black paint delivers noticeably better blacks that the white surface. The difference is more noticeable in person and the improvement does not just apply to a room with ambient light. White is known to be a more forgiving color but I found better color accuracy with the black surface too. It may be my fault for adding an additional reflective layer to the white paint but I saw more color shift from that surface
The pic below is a white paint / black paint comparison taken with the flash on my camera on.
The lower gain black paint mix with enhanced RGB reflectivity is far less affected by the bright light of the flash.
The headlines for all this are:
- I'm close to having a workable black screen paint mix
- Please don't experiment with untreated powdered aluminum at home - it can be very dangerous. Only uses treated bright aluminum powder
- all the ingredients I used are easily available
- Preliminary tests with gold and bronze metallic powders to enhance color vibrancy are really promising. More to come!
I plan to upload a video clip of a test for the black paint shortly which I think will do a better job of demonstrating it's potential. I am going to abandon side by sides with white screens for now (until I find a way to get it to a comparable gain). I will post separate pics of white screen tests for comparison though. To date, this is the only single layer black paint mix that I have seen that works. Does anyone know of any others?