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Big, Bright, and Not All Business:
Using A Commercial Projector in Your Family Room-Part 2

M. David Stone, February 13, 2019
Review Contents

Contrast & Black Level: Do you need an ALR screen?

You don't have to look much past our ANSI lumen measurements to see that all of these projectors can deliver a bright enough image to stand up to a high level of ambient light at a reasonably large image size. The least bright of the three—the LH770—delivers nearly 2,500 lumens after optimization, even in Eco mode, and just over 3,100 lumens in Normal power mode. The brightest—the G7905U—delivers just shy of 4,000 lumens in Eco mode using the color mode with the most accurate color, and a touch over 5,100 lumens in Normal power mode.

For context, on a 110-inch diagonal 1.2-gain screen, the lowest of these measurements—2,500 lumens—translates to roughly 84 foot lamberts (fL) or about 287 nits, which is in the range of a reasonably bright SDR LCD TV. The highest—5,100 lumens—translates to about 585 nits, which is well into HDR LCD territory.

So, yes, all of these projectors are bright enough for watching film and video in ambient light. But the numbers don't tell the whole story. In particular, they're silent about whether and how well these projectors perform with regard to contrast and black level under various lighting conditions, and whether or how much an ALR screen will improve the image in each setting.

To find out, we compared the image from each projector on two screens: a 1.0-gain standard white screen and Screen Innovations Slate 1.2 ambient-light-rejecting screen material (1.2 is the gain) in SI's Zero Edge Pro frame. The Zero Edge Pro comes in various fashion colors and with or without an LED backlight kit; our sample was conventional black with no backlight. (Further information and pricing can be found via the screen reseller links on SI's ProjectorCentral manufacturer page.)

Screen Innovations Zero Edge Pro ALR screen with optional LED backlight
Note that there are substantial differences between various ALR screen materials. We picked SI Slate 1.2 because it is one of the more popular choices out there, and we picked a 110-inch diagonal size for both screens as an appropriate—and common—size for a family room. The Slate material needs a minimum throw of 1.5 times the screen width for ALR to work well, so larger screens need bigger rooms to accommodate the minimum throw.

How We Tested

For each projector, we ran our tests with each screen separately, and then with half of the image on each to give a side-by-side comparison. For each of the three configurations, we used several lighting conditions. [BAN1]

All windows in the room were covered, giving us full control over lighting. Our three lighting scenarios were:

  • Fully dark, since some may want to turn off all lights to watch a movie at night
  • Typical room lighting at night, with high hat lights on the ceiling and assorted table lamps in the room
  • Room lighting plus daylight conditions. For the daylight conditions, we used lamps designed to replicate natural daylight and placed them in several positions—one position at a time—where a window might be on a wall perpendicular to the screen.
  • As a torture test, we also hung two lights on the ceiling pointing at the screen, the way you might light a picture on a wall. We wouldn't expect anyone to do that, but similar lighting conditions could happen unintentionally. In newer construction in at least some areas of the U.S., for example, cathedral ceilings with skylights are common in family rooms.

What's the Real Difference between Standard and ALR Screens?

As you would expect, we saw similar results with all three projectors, the only important factor being that the brighter the image, the better it stands up to ambient light. Given the overlap in brightness ranges of the projectors we tested with—depending on color mode, power mode, and zoom level—it makes more sense to discuss most of our observations in terms of what we saw at different brightness levels rather than what we saw with each projector.

ALR vs. Standard White. The first difference we noticed in the side-by-side tests is that because of the gray color and other SI Slate screen properties, the image was a touch dimmer on the ALR screen despite its higher gain. However, the brightness difference isn't enough to notice without seeing half of the image on each screen at the same time. And the trade off is that blacks are darker and contrast is better on the ALR screen in any lighting condition. So the ALR Slate has had an advantage overall even in a dark room

The second difference is that colors get shifted on the SI Slate screen compared with a matte white screen. The shifts are minor, and it just means that the projector has to be calibrated differently for each screen—no surprise there, and something every projection enthusiast should already know. You'll want to keep that in mind if you start out with a white screen and decide to replace it with an ALR screen. And if you need to calculate the appropriate projector brightness for a screen of a given size and gain at any given level of ambient light, it helps to know that SI says the calculations are the same for ALR screens as for standard screens.

In Dark Rooms. These projectors are such light cannons that with a 110-inch screen it is hard to make the images dim enough to meet SMPTE recommendations for viewing SDR images in a dark room. Forget the usual rule of thumb to aim for the 16 fL middle of the range. Even the top of the recommended range—22 fL—translates to less than a 700 lumen-requirement with a 1.0-gain screen at 110" and less than 600 lumens with a 1.2-gain screen. None of the models we looked at for this overview supports HDR. But note that even with the informal brightness recommendations for HDR, which range from 24 fL to as high as 50 fL (875 to 1,800 lumens for a 1.0-gain 110-inch screen), it's a challenge for these projectors to make the images dim enough for a dark room.

The ZH500T can go as low as about 625 lumens with sRGB mode and Eco, but only with the lens at its full telephoto setting. Every other combination of color mode, power mode, and lens setting for all of these projectors is brighter. The key takeaway here is that most of the settings on all three projectors are too bright for comfortable viewing for a long session in the dark. Unless you use a larger screen size, plan on keeping at least some lights on with most projectors in this class, if only at a low level, to avoid eyestrain.

Ambient light will also help hide any not-quite-black frame or letterbox bars around the image, which can be particularly distracting if they fall on the wall around the screen. Because of its native 16:10 aspect ratio, for example, the G7905U adds faint dark bars that show both above and below a 16:9 screen in the dark.

Night with Lights On. In our typical-family-room-with-lights-on scenario, many people will be satisfied with a standard white screen. However, the lower the projector brightness, the more advantage the ALR screen has.

Even at 6,200 lumens, the brightest mode we tested with, black is darker and contrast is better with the ALR screen. And the advantage increases at each step down in brightness. On the other hand, even at 3,100 lumens the picture is quite watchable on a standard screen without any killer shortcomings.

Ultimately, whether the ALR advantage for this ambient light level is enough at any given projector brightness depends on how demanding you are. Perfectionists will want ALR to improve black and contrast even at 6,200 lumens. I suspect that at 2,400 lumens, most people will want it.

Daylight. With our daylight scenario, you'll want the advantages of an ALR screen—period. Even with the brightest level we tested—6,200 lumens—the standard screen was unacceptably washed out on the side closest to the simulated window, no matter where we placed the lights. In comparison, SI's Slate ALR screen delivered a highly watchable picture at roughly 3,700 lumens and above.

The brightness cutoff below that is a judgment call. Even at 3,700 lumens and higher, the 10% or so of the screen closest to the window could look a little washed out, even with an ALR screen. This was dependent primarily on the angle between window and screen. If you can't adjust positioning to avoid the problem, and aren't willing to put up with a slightly washed out corner or edge, you can always add a shade or drapes to the offending window.

Previous Page
Color Performance
Next Page
Review Contents: Color Performance Contrast and Black Level Conclusion

Reader Comments(3 comments)

Posted Feb 14, 2019 7:25 AM PST


Post a Comment Alert Moderator
Very disappointed in the black and contrast level testing for the Optoma DLP laser projector. With the Optoma ZH500T, 920 lumens is too bright for dark screen viewing? On your home theater dlp lamped based reviews, where most "Movie modes" are a 1000 lumens, that has never been mention as a problem.

Also the ZH500T has a "ExtremeBlack" feature that modulates the laser for better blacks levels and contrast. Why wasn't that mentioned? Was it tested? Why no actual report on how good or bad the black levels are? Are they more dark gray than black or are the better than lamped based projectors when the lumen brightness are matched?

Posted Feb 22, 2019 8:11 AM PST

By bob osterman

Post a Comment Alert Moderator

I don't think the article says that 920 lumens is too bright for dark screen viewing. I read it as saying that for a 110 inch screen, 920 lumens gives a brighter image than the 22 foot lamberts that SMPTE recommends as a maximum. All that means is that you need a bigger screen than 110 inches.

Posted Feb 22, 2019 8:41 AM PST

By Rob Sabin, Editor

Post a Comment Alert Moderator
Bob's more literal interpretation is the correct way to read this, as the reference here is to the SMPTE recommendation for dark-room viewing. And yes, a larger screen would obviously reduce the brightness.

To Michael's point, though, the comment is perhaps not properly placing this in full context of our overall experience. In reality, we typically measure something between, say, 600 and 950 lumens of brightness on a Cinema or Film mode, the variance being the difference between the least bright and most bright lamp mode. So maybe this 920 lumens referenced would be acceptable, but without any ability on a "typical" 110-inch screen to reduce the light output to something more comfortable than what a high lamp mode would generate. That simply may be too bright and fatiguing for some people.

But I think there's a more subjective debate to be had here about how bright is too bright in terms of a peak-white reading OFF the screen these days (lumen measurements are taken facing the lens). Our columnist Terry Paullin, who has built home theaters for 30 some-odd years, recently wrote that he recommends a projector with enough output to generate a minimum of 25 ft-L coming off the screen and personally likes it up around 40 ft-L for his own viewing. (See his article here.) That 25 to 30 ft-L is a nice target for an HDR viewing mode on a 4K projector in actual use, but may be too bright for long-term viewing in a dark theater with SDR content for some people. But it won't be for others. I also lean toward a brighter pictures, and may end up with a measured 35 or so ft-L off the screen in SDR for a 100 IRE, 18% window (not full frame). For the HDR mode, it can be as high as 50 or more ft-L if the projector accommodates. Of course, you're viewing those 100% peaks very infrequently and the average picture level of most content is well below 50%.

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