I have a Vikuiti black rear screen sample and it is pretty incredible compared to everything else that I've tried. I read that it uses microspheres on the back of some sort of black 3M film.

What I was wondering is are these the same type of microspheres used on retroreflective front projection screens (like the Greywolf) except with an anti refective coating to allow light to pass through more rather than be reflecting back too much?

I ask because I've been reading up on retroreflective paints and hope that in the future it would be possible to make a DIY black rear black screen that can focus the light similar to a fresnel screen (like the Vikuiti does) without needing an incredibly expensive fresnel screen on the back.

The Vikuiti is nice, but really expensive, so I'm hoping that it would be possible to make a DIY version (at least fairly close) in the future. The second best rear screen that I've tried is the Dazian grey screen, which is nice, but it's not nearly as tolerant of HIGH ambient light as the vikuiti, nor as bright.

I am interested in the same thing, the vikuiti is good with ambient light but way too expensive.
If anyone has exerience with something DIY please let us know!

I will post if I come across anything.

Thanks!

I don't believe the Vikuiti collimates light like a Fresnel, it's just good at absorbing ambient light.

I don't believe the Vikuiti collimates light like a Fresnel, it's just good at absorbing ambient light.

It must to redirect light to some extent, otherwise it would hotspot big time with gain that high. The gain is VERY high compared to my 1.8 gain Dazian grey screen or the near black vinyl rear screen I've tested. I have tested other high gain materials like translucent frosted vinyl and it hots pots like crazy. The only way to possibly get around that is with a screen that can redirect light or with more diffusion (ie lower gain). The Vikuiti appears to have near even brightness throughout, despite its high gain. The near black vinyl rear screen I tested only a fraction of the brightness of the Vikuiti.

The Vikuiti is a black film layer with embedeed mircospheres and a very thin frosted diffusion surface. I noticed that when the screen material is peeled off of the arcylic front the optical microspheres become retroreflective on the back.

The microspheres are definitely redirectly the light, otherwise it wouldn't make sense to have them, because you'd just end up with a hot spot with the increased gain.

"It must to redirect light to some extent, otherwise it would hotspot big time with gain that high."

That's a conflicted statement - redirecting the light forward like a Fresnel does is precisely the reason it has a narrow viewing cone.

"The microspheres are definitely redirectly the light, otherwise it wouldn't make sense to have them, because you'd just end up with a hot spot with the increased gain."

If my understanding is correct, it's very similar to the Jenmar Blackscreen, where the purpose of the micorospheres is to gather and send the light out through small areas, while the surrounding black matrix absorbs ambient light.

There's a tiny picture that came along with the info and it shows the light path being altered a bit by the optical microspheres. It shows the light hitting straight on in this case. There are two lings representing light; one on top and one slightly below. It shows the single microsphere making the two lines exiting the screen crossed together like an "X". The top line declined down at a 25-30 degree angle and the bottom line inclined upward about the same and they cross paths just as they exit the black layer.

MTyson,

the Vikuiti has a gain of 1.1 - what other types have you sampled? Brightness uniformity should be good but I can't see it being any brighter than other diffusion screens with about the same gain.

(otoh, my Draper Cinescreen 13 claims gain=1.3 but in reality it's much less)

As for DIY, the Vikuiti tech can also be bought as a rear projection adhesive film. Width = 1200mm. I have no idea how to laminate this onto a transparent substrate. Wet or dry? I don't even know the difference, but it's mentioned in this data sheet:
http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs66SHyBCOrrrrQ-

Wow? Only 1.1? That's surprising, but now it makes perfect sense. I have a 1.8 gain Dazian dark gray rear screen and it doesn't seem as bright as the Vikuiti (in ambient light). I guess it's not really so much that the Vikuiti is brighter now. I guess the ambient light rejection is just so good that the super high contrast gives the illusion of higher gain, because there is less washout. Interesting. Well, I knew there had to be some reason why it has such a wide viewing angle while appearing so bright.

I've also tried a frosted clear vinyl sheet. This one definitely had very high gain, because it hot spotted big time. I could see the projector's beam in the middle. However, it didn't have close to the same contrast in ambient light as the Vikuiti or Dazian Gray rear screen, so maybe that's what makes the Vikuiti seem so bright in comparison, contrast from having less picture washout in ambient light.

The Dazian dark gray rear screen does quite well in a little ambient light, but it's still no match for the Vikuiti, especially in higher ambient light. I guess it's not because of gain, but because the black layer is so effective along with the microspheres.