Projection Screen Reviews

To keep the measurements within useful bounds, I elected to test for brightness and color uniformity across the width of the screen at its vertical center. For the tests from a centered seating position, the readings were taken only from the center to the left edge, on the reasonable assumption that the results would be essentially the same at the same distance from the center in all directions.

Rather than absolute results, the measurements here are a comparison of the Elite CineWhite material used in the Osprey) with three other well-known and widely respected screen materials: A Stewart StudioTek 130 G3 (specified gain 1.3), a Stewart StudioTek 100 (specified peak gain 1.1), and a Da-Lite Affinity (specified gain 1.1). The projector was the Digital Projection M-Vision Cine 230-HC single-chip DLP in its Standard (high) lamp mode.

Since the Elite was the only full 2.35:1 screen we had on hand, measurements on the other materials were taken on small screen samples, positioned at the measurement points and as close as possible to the plane of the Elite.

First, I checked the gains of all four screens at the center. True gain is typically measured by comparing the luminance of the screen under test with that of a special testing surface called a Lambertian diffuser. The latter disperses the light falling on it uniformly in all directions—the primary characteristic of a screen with 1.0 gain. But here we elected to check the gains of three of the test screens relative to the gain of the StudioTek 100 by assuming that the latter is a uniform 1.1 (peak), as specified, across as wide a frontal angle as we planned to check. That’s also a reasonable assumption; Stewart uses a Lambertian diffuser in designing and specifying their screens. We could just as easily have chosen the Affinity; both are widely respected references.

Results are shown in the chart above. The measured on-axis gains (Column A) are close to the manufacturers’ specified values (assuming our reference is precise).

Note in particular the change in gain across the screen. It’s natural for light to fall off from the center to the sides, due to both the screen and the projector. Since we’re comparing screens at identical positions, the effect of the projector here drops out of the mix. As we move further off axis, either at 9.5 degrees (half the distance from the center of the screen to the left edge, Column B) or 17.5 degrees (just short of the left edge, Column C), the gain of each screen drops except for our assumed perfect diffuser, the StudioTek 100. The other screens with specified gains of 1.1, including the Elite, come very close to that. If you need more brightness for most seating positions, the 1.3-gain (1.34 as measured) StudioTek 130 is a reasonable alternative, though as the chart shows, it has greater brightness falloff closer to the sides of the screen—as will any screen with significant gain. The higher the gain, the more the off-axis brightness decreases.

Column D shows the change in gain from the center to the left side as a percentage. The eye is relatively insensitive to such brightness decreases—up to a point. While experienced viewers may notice the 25-percent loss at the far edge in the StudioTek 130, it’s doubtful if anyone will notice the 12-percent drop in the Elite.

I also measured the loss in brightness from the left side of the screen to the right, as measured at a seating position about 20 degrees left of center. This is shown in Column E, this time in foot-lamberts of brightness—which will include the effect of the 230-HC projector. This is roughly what you’ll experience when sitting on the left side of a very wide sofa located 12.5 feet from a 101-inch-wide screen. You can see that from this location, the left side of the screen (closer to you) won’t look obviously dimmer than the farther-away right side—even on the StudioTek 130. This is important, as I have seen clearly visible side-seat dimming in the past from special-purpose screens such as the Stewart FireHawk and the Screen Innovations Black Diamond.

I also measured how the color shifted on all three screens from the calibrated center to the left side. The change, which wasn’t visible to the eye, was measurable but largely negligible, and likely due as much to the characteristics of the projector as to the screen itself.—TJN