Projectors Reviews, price and comparision

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The Severtson GP169923D ($1,150 street), which Severtson describes as a Portable Projection Screen Pull-Up with SeVision 3D GX Screen Material, counts as an impressive portable screen in two very different ways. First, as a more or less portable screen, it's extraordinarily easy to set up and break down. And second, the screen material is also far from ordinary. Designed for 3D, it does an excellent job handling 3D images. Unlike some 3D screens, however, it handles 2D well also. The result is a single screen you can use for all your projection needs, which is enough to make the GP169923D both literally and figuratively an attractive choice.

A word about the portability first. Like the 80-inch diagonal Optoma DP-MW9080A ($350 street, 4 stars), which it physically resembles in some ways, the GP169923D isn't really portable. It's light enough, at 20 pounds, so you can carry it with you from one place to another, but the case, when closed, is 3.1 by 86.4 by 2.4 inches (HWD), making it more than a little hard to carry around without banging into walls, furniture, or people.

Arguably the best use for the GP169923D is in a single room—whether a conference room, classroom, or family room—where a permanently installed screen isn't an option. Set it up, and it's big enough for an impressively big picture, at 92-inches diagonally with a 16:9 aspect ratio (80 inches wide by 45 inches high). Close it, and it's small enough to sit unobtrusively against the base of a wall. It's also light enough to pick up easily to move short distances, including from room to room, and it has a handle to make it easy to carry. But be careful not to bump into things.

Setup

When I reviewed the Optoma DP-MW9080A , I said (foolishly, it turns out) that it was hard to imagine how any non-permanent screen could be easier to set up. The GP169923D is much easier.

The first screen Severtson sent for review used a frame virtually identical to the one that the DP-MW9080A uses, with an adjustable arm in the back that swivels up to be perpendicular to the floor. You can then lift the screen by the same handle you use to carry it, hook it on the arm and adjust the arm height. The process takes 30 seconds or less. When I mentioned the similarity to a Severtson representative, however, he said the company no longer uses this frame (although the screen material is the same).

The only screen with the newer frame that Severtson could send me quickly was a smaller model, roughly 55-inches wide, but the company says that the larger frame works exactly the same way. In any case, I've never seen a portable screen this easy to set up.

You first pivot each of two feet—one near each end—so they're perpendicular to the case and can give the screen better stability. You then press the release button, grab the top of the screen and lift it to unroll the screen from the case. In addition to the screen material itself, there's an additional black section below it, so the entire viewing area can be well above the base.

Unlike the earlier version of the frame, the height of the screen is infinitely adjustable, thanks to a spring-loaded accordion-style support behind the screen. There's no supporting arm to hook it on or that you have to adjust to the right height in a separate step. Instead, you move it up or down simply by lifting it or pushing it down. Total setup time is only a few seconds to pivot the feet plus about a second for lifting the screen. Closing it to put it away is just as fast and easy.

The SeVision 3D GX Screen Material

Although the frame makes the GP169923D easy to use, what makes it a 3D screen is its screen material. As I discussed in my review of the Volfoni SmartCrystal Pro ($1,500 street, 4 stars) if you want to use passive glasses for stereoscopic 3D with a projector, you not only need the right hardware to project the image, you need a 3D screen.

Stereoscopic 3D works by alternating between frames for the left eye and frames for the right eye. It also needs some mechanism to make sure each eye sees only the frames meant for that eye. Your visual system then integrates the two sets of frames to see in 3D. With passive 3D glasses, the mechanism that separates out the frames is polarization. The two sets of frames for the left and right eyes are polarized in different directions, and so are the lenses in the glasses, so each eye sees only those frames that are polarized in the right direction for that eye.

Standard white or gray screens for 2D and for active shutter 3D glasses won't work with passive glasses. Shine polarized light on them, and they turn it into non-polarized light (or, more precisely, randomly polarized light). What you need instead is a silver screen material, which retains the polarization when it reflects the light. These silver screens are generally called 3D screens. Many are suitable only for 3D, typically because they reflect light unevenly, which shows as hot spots on the screen with 2D. Home theater enthusiasts often wind up with two screens as a result, switching between a 2D and 3D screen as needed.

One of the strengths of the SeVision 3D GX screen material is that, like some other 3D screens, it's suitable for both 3D and 2D, thanks to what Severtson touts as an "amazing" uniformity of gain and texture. Indeed, in my tests it worked just fine with both kinds of images.

Other Screen Material Issues

The screen material also offers other some important features that affect the viewing experience, starting with a 2.4 gain. At the risk of oversimplifying a bit, screen gain tells you how bright the reflected light from the screen is compared to what you would expect from a white surface that reflected light equally well in all directions.

A 1.0 gain screen is equally bright from any viewing angle. A high gain screen like the GP169923D is noticeably brighter from directly in front of the screen than from, say a 45 degree angle, because it's reflecting more light directly back than to the sides.

The advantage of a high gain is that if you're sitting in the right position in front of the screen, you'll see a brighter image than you otherwise would. The disadvantage is that with some seating arrangements, which you may have in a conference room, for example, some seats may be far enough to the side for the image to be noticeably dimmer.

With the GP169923D, the specification for gain drops below 1.0 at a little less than a 30 degree viewing angle. At 45 degrees it's 0.5. As with any high gain screen, if you can't arrange your seating to keep everyone within an appropriately narrow viewing angle, the high gain could be more of a problem than an advantage.

One other specification worth mention is the extinction ratio, which may need a little explanation. Even 3D screens don't do a perfect job of maintaining polarization. Some of the light in each frame becomes randomly polarized, so you'll see it with the wrong eye. The more light that becomes randomly polarized, the brighter the unwanted image will be and the easier it will be to see, in the form of a ghost image, or crosstalk.

The extinction ratio tells you the brightness ratio between the frames you're supposed to see with a given eye and the ones that are meant for the other eye. The higher the ratio, the dimmer the wrong frames are in relation to the right ones, and the less crosstalk you'll see. An extinction ratio of 150 is considered pretty good. SeVision 3D GX claims a bit over 250. As with gain, the extinction ratio drops rapidly with viewing angle, falling to 150 at 21 degrees, hitting 100—which is still a reasonably good level—at 27 degrees, and falling below 50 at 45 degrees. Not surprisingly, in my tests, I saw obvious crosstalk at a 45 degree viewing angle, but not when I was sitting directly in front of the screen.

Ultimately, the GP169923D is a highly attractive choice. The screen size is big enough to let you project a relatively large image, and it's easy to set up and easy to put away, which is an important issue for a screen that you'll be setting up repeatedly as needed.

The screen material is certainly the main attraction. The high gain will be a plus in some circumstances and a problem in others, but that's true for any high-gain screen. Quite simply, if a high gain isn't appropriate, you shouldn't be considering any screen that offers high gain. Similarly, if you don't need a 3D screen, there's obviously no reason to spend the money for one. However, if you want a single, semi-portable screen both for 3D with polarized light and for 2D, make sure you include the Severtson GP169923D on your short list. It's unquestionably worth a close look.

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