HOME > Ambient Light Rejection screens from Elite, Screen Innovations, and Microlite
Ambient Light Rejection Screens
August 5, 2015,
EDITOR'S NOTE: This article has been expanded and updated to include eleven current models of ALR screens. Please click here for the new review.) 3/03/16
ALR screens aren't meant to be used in ideal home theater spaces. They're meant to bring projectors into rooms where ambient light, white paint, or other circumstances would otherwise make projectors unfeasible. So to test these screens we installed them in a room with a large window and white walls to see how they perform in environments for which they are built. In theory, the projector used for these tests should not matter; all tests were conducted with the same projector and in the same environment. To give you a general idea, we used an entry-level DLP home entertainment projector rated at just over 3,000 lumens and 15,000:1 contrast, and all tests were conducted after the projector had been given an opportunity to warm up for 30 minutes. Our reference white surface, used for comparison purposes, was tested and confirmed to have a gain of 1.0 exactly.
Peak Gain and Half Gain
The three screens in this shootout differ in their peak gain attributes. Higher peak gain means a brighter image when viewed from the center position, but it can also mean hotspots, shimmer in the image, or uneven screen illumination, so higher gain is not always better. Sometimes a brighter projector and a lower gain screen yield a more balanced, natural image than high gain and lower lumens.
In this test, the Microlite F2.0 had the highest peak gain at 1.74, essentially matching its peak gain rating of 1.8. Similarly, the Screen Innovations Slate measured a peak gain of 1.18 in conformance with its spec of 1.2. However, the Elite PolarStar measured a peak gain of 1.55 which is notably higher than its rating of 1.3.
As expected, the SI Slate showed the fewest gain-related artifacts; it had no shimmer worth mentioning and no noticeable hotspots. The Microlite F2.0 did have a slight "oil slick" appearance at times, but there were no hot spots unless you made it a point to stand outside of the ideal vertical viewing area. At this point you might notice a "hot band" -- a horizontal stripe across the screen that's brighter than the rest of the image. Sitting in the proper seating location, you can't see any hot spots despite the high gain. On the PolarStar, there's no oil slick, but there is sparkle at times, which some users may find distracting.
The half-gain angle is the viewing angle at which the reflected image is half as bright as when viewed from the center along a perpendicular axis to the screen surface. A wide half-gain angle is helpful if you want to place seating at wide angles to the screen, as it means people seated in these positions will still see a reasonably bright image.
The Microlite F2.0 screen had the widest half-gain angle by far, measuring 56.5 degrees in either direction. In comparison, the Elite PolarStar (25 degrees) and Screen Innovations Slate (21 degrees) offer narrower viewing cones and therefore appear significantly less bright to people sitting off to the sides. Half-gain angle only measures one side of the viewing area, so the brightest viewing area can be determined by doubling those measurements. Closer to the center is better.
Contrast / Ambient Light Rejection
The easiest way to decide which screen is rejecting the most ambient light is to put them all in the same situation and then measure contrast. We conducted three tests: one with lights off and windows completely blocked, one with an overhead light on, and one with the side window shade open. In all three tests, we compared the screens against a reference white screen in order to judge their ability to reject ambient light. We used the same projector for all tests, and we measured from the ideal viewing angle for each screen.
Dark Room Test. First, a point of clarification: our "dark room" in this test has white walls and a white ceiling, meaning it's not very dark at all. In a properly blacked-out home theater, there should be very little performance difference between an ALR screen and a traditional white screen.
We measured black and white levels on each screen as well as our reference white surface using an ANSI checkerboard pattern. The best performing screen was the Microlite F2.0, measuring 217:1 contrast. The Elite PolarStar and SI Slate 1.2 measured 148:1 and 129:1, respectively, which is not a perceptible difference if you aren't using a meter. The reference white surface measured 86:1. In other words, we saw clear benefits using any of the ALR screens even in a room where the only light pollution comes from reflection.
Overhead Light Test. During the next test, we turned on the room's overhead light. This room is normally used as a library and has a pair of 100W equivalent CFL bulbs in a fixture on the ceiling, giving us enough light to read by without straining our eyes.
Contrast took a hit on every screen, with the Microlite F2.0 dropping to 146:1. This still beat out the PolarStar at 110:1 and the Slate at 92:1, but all three screens did far, far better than the reference white surface at 39:1.
Side Window Test. The east-facing window in our test room has a blackout shade that was closed up until this point. For the final test, we turned off the overhead light and opened the shade, letting in some mid-morning sunlight. This had a dramatic effect on contrast. Under these conditions, the PolarStar performed best, measuring 73:1. The Microlite F2.0 measured 61:1, while the Slate measured 50:1. Our poor, abused white screen, unaccustomed to this much ambient light, measured a paltry 20:1.
Our testing revealed some interesting findings. Given how the Microlite F2.0 performed in the first two tests, we fully expected it to triumph in the third test as well - but it didn't. Instead the PolarStar pulled out a win. This tells us that the Microlite F2.0 material is a great choice when ambient light is vertically offset from the projector, but less effective at combatting side lighting. In a room with strong side lighting, the Elite PolarStar is an excellent option.
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