Screen Innovations Black Diamond II
Ambient Light Rejection Projector Screen
Light output curtailed. Like the first Black Diamond, the BDII is a low gain screen, listed as 0.8 gain. In our lab, we measured an actual gain of 0.7. This means that the screen reflects 70% as much light as a 1.0 gain white surface. If you're used to watching your projector in a dark room on a 1.0 gain screen or higher, the Black Diamond will make your projector appear dimmer than before. Accordingly, the Black Diamond works best with bright projectors, or with the brighter operating modes on projectors that give you various options in this regard.
Color shift. The Black Diamond II tends to make the image from your projector appear slightly colder; that is, it appears slightly blue in tint when set next to a more neutral screen. The easiest fix for this problem is to go into your projector's menu system and reduce blue/add yellow. Of course, if you find that the slight blue shift doesn't bother you, there's no need to change anything.
Brightness uniformity. Ambient light rejection screens mostly reflect light which hits the screen more or less dead-on center - such as the light coming from your projector. It reflects most of this light directly back towards the projector. So it is important to keep the level of the projector as close to the center of the screen as possible. If you are ceiling mounting, the projection angle can be enough to create some very noticeable brightness uniformity problems in which the upper half of the image looks much brighter than the bottom half.
Narrow viewing angle.Screens have what is called a Half-Gain Angle. That is the viewing angle at which the screen reflects half as much light as the viewer would see when sitting directly in front of it. On a typical low gain screen, this could be as wide as 60 or 70 degrees. On ambient light rejection screens, it is typically much narrower. On the Black Diamond II, we measured a half-gain angle of 22 degrees. This gives you a 44-degree window in which your audience can sit for optimum image brightness and clarity. Sitting outside of that, the image will appear less than half as bright as it does sitting dead center. You've seen this effect on rear-projection TVs. They look bright when viewed head on, and they dim rapidly as you move off axis.
Below are the results of our viewing angle tests. The images, in sequence, are: in the "sweet spot," 22 degrees off-angle to the left, and 35 degrees off-angle to the left. As you can see, the image looks wonderful from the sweet spot - color is vibrant, contrast is impressive, and the image looks sharp and detailed. Moving a bit to the left, we see the right edge of the image start to dim. By the time we get to 35 degrees off axis, it's obvious that the picture quality is severely compromised. To put it in simple terms, most users will have about one couch-width of a sweetspot to work with. Anyone not sitting on that couch will have a less than optimal view.
Tricky assembly. The Black Diamond II's unique screen material is delicate, as the instructions indicate - there are several warnings about scratching or bending the material during installation. If you put a dent in the material, it won't come out. There's even a pair of latex gloves in the installation kit.
The screen attaches to the frame by way of rubber bungees, which loop through the screen material in pre-punched holes and attach to posts on the frame. It takes some getting used to, especially using the "installation tool" (a length of rigid plastic tubing). But we were able to get it together in about half an hour. Of course, if you're buying the Black Diamond II from a custom installer, chances are they will put it together for you.