Not ignoring the work with mylar. Infact, it is one of the things I was / am waiting to try and my mylar sample was among the goodies that got delivered today.
I have never worked with mylar before although looking at it now, it seems similar to the mirror tinted window film I have tried. More reflective maybe. It looks different to how it behaves in a way I don't really understand. The surface looks like a mirror but it is also a little see through. The reflection is nothing like a mirror. I am not sure if there are multiple types of mylar (other than thickness). Here is a pic of the one that came and the reflection from the projected image. A mirror would reflect a watchable image, the mylar reflection was somewhat more diffused.
One of the things I like about films generally (for painted screens) is that the surface is smooth so you end up with a nicer painted layer on top. For the tests in the following pics, I tried both mylar and a matt aluminum plate to see the difference. Although the purpose of these tests was to find a good diffusing and tinted layer for the front surface, It is also useful to try a few different reflective surfaces to see what works. I was pleasantly surprised with the test films. These were not the ones I had the highest hopes for. Instead, I think I found some viable options that offer both tint and light diffusion with no hot spots.
Specifically, this dark grey film. It has a matt finish on one side and a glossy finish on the other. I projected onto the matt side and saw no hot spots from any angles which is a goof start. Here is a pic of the film. I have some darker films coming but this is the darkest for today. I tried it with just a reflective surface behind it and with some additional tint.
Here is what is looks like with a piece of aluminum behind it.
Not very black diamond 0.8 gain. Perhaps somewhere between the BD 1.4 and 2.7 colors but still looks kinda flatsecreen TV-like with the dark tint over metal.
I also tried it with some additional tint and it looked much closer to black:
Before I show the results of my very crude initial tests, here is a pic of the comparison screen:
This is my white wall screen, not the normal grey screen I use for comparison. It's a tough day for the white screen. The angle it is at makes daylight stream in from the side washing out one side more than the other. I would probably never try to watch like that with any screen for uniformity reasons. Dealing with light is easier if the whole screen is equally impacted. The projector in use is 2500 lumens. Today is less about ambient light capability and more about finding a front layer that is smooth like a film but doesn't hotspot. The other layers will take care of the light (hopefully!). Ok, here is a shot of the result: The first one is with just the film and aluminum plate behind it. I like it!
It's hard taking pics when it's just me on my own but from my seat, I was really please with how it looked. I couldn't make it hotspot from any angle I tried. It made me smile. Here is a pic using mylar as the reflective layer:
Bottom line is that the mylar works as a reflective layer. It is far harder to take a picture of in a crude test though. It wrinkles easily with a slight finger movement and if it isn't 100% smooth, the creases are visible through the film and cause a shimmer. Now, if I used Mylar instead of aluminum, I would need to find an alternative rigid surface to attach it too. I am assuming that once attached to some wood or plexiglass, this wouldn't be an issue. Mississippi Man (hope I spelt that right!), in your experience, what is the best way to attach mylar to a rigid surface? I have various types of glue and resin. One of the things I found with other mirror type films was that they are the only thing that epoxy resin doesn't stick to. Does it need a specific type of glue?
Here is a pic at the right angle of the grey film with a privacy filter behind it and aluminum behind that. The privacy filter is for extra tint for those who like a really black "black-screen". From the front, it actually works well.
From the side, the privacy filter blocks the reflectivity of the aluminum and the image goes dark:
Now one could ask the question, "what is the point of testing the privacy filter when you can't find one big enough?". I decided that if these filters were used as a second layer, multiple filters would be attached to the reflective layer and the seams would be hidden by the top layer. I actually tested this theory. Don't laugh at the following pic!
I can here you laughing!
Now, i am not sure I would recommend the privacy filters unless you are determined to make it reject light from the sides and above. I happened to get lucky on an ebay auction and got 50 iphone privacy filters for about $20. I don't have an Iphone so I could use them all for testing. With a little luck and a determined DIYer, a decent sized version could be made for less than $100 - $150. If anyone wants to go that route, I would suggest going for the older 2 way privacy filters and choosing to reject light from either the sides or above. I found that doing both gave me a viewing cone that I wasn't happy with. The other thing I would say, is that some are darker than others and some have a more regular shape. Go for the lighter ones and avoid ones where you will have to cut off too much of the filter to give you straight even edges.
Here is a pic of the grey film with aluminum backing and regular window tint added behind it:
I took this pic from the washed out side of the screen where there was the most direct sunlight. I want to repeat that test when I get some new tinted films. I guess the overall comment is that individual will need to select the type of tint based on their preferences and how bright their room it. The other point is that a darker tinted film can be balanced with a lighter front film (again based on preference). People with a really bright projector may want a 50% tint vs a 70% for a regular home theater projector. The other aspect is the reflective layer. The mylar was a little brighter than the matt aluminum and could therefore stand a slightly darker tint. With a polished aluminum surface or even a glass bead surface, it could be different again.
Here are some other films that I tested today:
More for comparative purposes, this is a relatively inexpensive front projection film. Not massively relevant to this except as a baseline for me.
This one is similar to the grey except a lighter shade. It is creatively called "light grey"
Over aluminum, it also has that plasma kind of look:
More BD 2.7 than BD 0.8. It would need a darker tint to get a blacker appearance.
The next one is a frosted film with a matt side. To get a black-screen appearance and effect, it needs an additional darker tinted film underneath but it works well like that.
Here is a pic of the frosted film with a light tint underneath and aluminum under that. It can go to dark grey with darker films although, if darker is the preference, I think the dark grey film is better up front.
I did also try a transparent film and it didn't work for me. Even on the matt side, I got hotspots. Not much use for a black-screen anyway but here is a pic of the problem just so you can see.
Here are some of the results. I have loads more pics but I'm limited on time right now. I can post more later:
Light grey with aluminum back
Frosted film with 50% tint and aluminum. My hand is there because if it is not touching all surfaces, the images gets distorted (one reason why I need an assistant!)
The surprisingly good front projection film - almost like a disposable silver screen.
The dark grey film use for rear projection - I always like the way that looks. Shame i don't have the room for it...
This is a completely different rear projection screen with an ultra short throw. This screen is a light charcoal and in my opinion, doesn't work as well as the darker film pictured above for the black-screen experiment. Still, a useful comparison.
I know these are all crude and I will do more testing to see. I just couldn't wait once I saw they had arrived! I have to go now but I'll post more pics later on or tomorrow. I have some new films arriving either tomorrow or the day after. Specifically, there is a dark grey (nearly black) material that I have high hopes for. I will upload some video clips too. They seem to be better than stills for showing this kind of thing. I'll keep you posted!
Does anyone know why a fabric being black reduces the viewing cone? Or if the same applies to really dark grey?