Ambient Light Rejection Screens

Evan Powell, March 3, 2016

Viewing Angles and Half Gain Angles

Contrast as viewed from the center position is only one of several factors that contribute to image quality and screen functionality. A second vital factor to consider is the viewing angle -- what does the picture look like when viewed from a position other than dead center zero degree viewing axis? These eleven screens behave quite differently in this regard. Some quickly get dim the moment you move away from a center viewing position and others remain remarkably bright even when viewed from an extreme side angle.

The statistical measurement used to quantify this phenomenon is the half gain angle. This is the angle at which the center of the picture appears to be half as bright as it does when viewed along the zero degree viewing axis. A screen with a small, narrow half gain angle will look bright at dead center, then quickly become dim as you move to the side. Conversely a screen with a large, wide half gain angle will continue to look reasonably bright as you move away from center.

On ambient light rejection screens in particular, not only does the screen begin to dim when you move to the side away from center, but the brightness uniformity degrades as well. When you view from the position of the half gain angle, the center of the screen is half as bright, but the far side of the screen is much dimmer than the near side. This is about as bad as you'd want it to get, so viewing at an angle greater than the half gain angle is considered to be unacceptable from an image quality perspective.

On spec sheets and in promotional literature, vendors often use the technical term viewing angle instead of half gain angle. The viewing angle is double the half gain angle. Why? If a screen has a 30 degree half gain angle it will look half as bright as it does when viewed from the center position if you move either 30 degrees to the left or 30 degrees to the right. So the total "viewing angle" is considered to be 60 degrees.

There is nothing inherently good or bad about wide or narrow viewing angles, but it means that you need to choose a screen that will meet the needs of your anticipated audience -- If you have a small viewing room with two or three seats placed in front of the screen near the zero degree viewing axis, a screen with a narrow viewing angle will be just fine. On the other hand, if you expect people to be viewing from very wide angles, you will need a screen that will give them a bright and relatively uniform picture when seen from the sides--that is, a screen with a very large, wide viewing angle.

In our ambient light mid-day set up, we put our spot meter on the center of each screen when viewed at zero degree axis, and then moved to the side toward the direction of the incoming ambient light to find the angle at which the meter was reading half the amount of light it was at dead center. To avoid confusion, we give you both the half gain angle and viewing angle for each of the screens in this review:

Screen
Half Angle**
Viewing Angle**
Da-lite Parallax
85
170
DNP Supernova
85
170
Elite EVP DarkStar 9
85
170
Microlite Black Crystal 1.2
70
140
Draper MS1000X
32
64
Stewart Firehawk G4
32
64
Elite DarkStar
30
60
Elite EPV PolarStar
30
60
SI Black Diamond 1.4
30
60
SI Zero Edge Slate
23
46
Seymour Matinee Black
16
32
** For comparative purposes only. These ratios show how the screens responded to this particular ambient light condition with this particular projector. They may or may not match official screen specifications.

Vertical Half Gain Angles

Not only do screens begin to lose brightness and uniformity when you move sideways from the center viewing axis, they typically lose brightness and uniformity if you move up or down and look at them from either above or below the center neutral position. This phenomenon is measured by the concept of the vertical half gain angle, which is the angle above or below the center neutral viewing axis at which the picture looks half as bright as it does at the center position.

A screen with a narrow vertical half gain angle will require precise placement of the projector at an angle exactly complementary to the vertical viewing angle of the audience. Slight deviations from this angle may introduce vignetting, uniformity, and brightness issues. A screen with a wider vertical half gain angle will allow more latitude in the vertical positioning of the projector relative to the audience.

The screens in this review measured the following vertical half gain angles under the ambient light conditions used for the Contrast Test 1:

Screen
Vertical Half Angle**
Stewart Firehawk G4
40
Draper MS1000X
35
SI Zero Edge Slate 1.2
26
Seymour Matinee Black
23
Elite DarkStar
20
SI Black Diamond 1.4
20
Da-lite Parallax
18
Elite EPV PolarStar
18
Elite EPV DarkStar 9
18
DNP Supernova
17
Microlite Black Crystal 1.2
15
** For comparative purposes only. These ratios show how the screens responded to this particular ambient light condition with this particular projector. They are not official screen specifications.



Review Contents: Overview Contrast Half Gain Angles Black Levels
  Peak Gain Texture Artifacts Color Bias DaLite Parallax
  DNP Supernova Draper MS1000X Elite DarkStar Elite EPV DarkStar9
  Elite EPV PolarStar Microlite Black Crystal SI Black Diamond SI Zero Edge Slate
  Seymour Matinee Black Stewart FireHawk G4

Reader Comments(10 comments)

Posted Jul 27, 2017 3:45 AM

By Lee

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Is there a conclusion anywhere in the article? Great article, but would be great with a short summary section!

Posted May 11, 2016 11:04 AM

By Tuki

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It would be nice to include the high gain Vutec SilverStar 6.0. Thank you.

Posted Apr 9, 2016 12:18 PM

By Scott Tallal

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Hi Evan,

This review has been incredibly useful! We only wish you would have included at least a few of the high gain options, most notably the dnp SuperNova 23-23 and the Screen Innovations Black Diamond 2.7. Perhaps you can do a shootout between those and other high-gain options in the not-too-distant future?

Keep up the great work!

Posted Mar 31, 2016 8:09 PM

By Jason

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I'd also like to see the Elite Cinegray 5D does in the tests.

Posted Mar 17, 2016 4:22 AM

By Mishari

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I wish you added 2 points: - contrast measure at all lights off to see they have better contrast than white screen. Some of us do not want to have dark walls and ceilings. - Add Elite Cinegrey 5D, which is highly available to public and well reviewed.

Posted Mar 16, 2016 8:14 PM

By Tomas

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Hmm, how come here is missing Black Pearl HDR from SimPit? Unrestricted viewing angle, exceptional black levels and color ... and one of most affordable ALR screens as well

Posted Mar 13, 2016 8:04 PM

By Rob Hunt

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Excellent review, very detailed. However, i think it would benefit readers to have a large television also tested along side these screens, since that is the screens biggest rival. some 75 inch tv around the same price as a screen/pj setup. Then viewers could understand the magnitude of the benefits and drawbacks of a ALR setup.

Posted Mar 6, 2016 7:04 AM

By Hector

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Excellent review. I wished I was there while you were doing the reviews :) I have been looking for unbiased review on ALRsa d you have exceeded my expectations. Thanks again!

Posted Mar 4, 2016 5:12 PM

By Paul B

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What a great review of multiple ALR screens. I can't thank you enough as I am completing a basement remodel and have been searching for ALR screen reviews and challenged by the limited information, as well as critical details about how the products were tested. Having all of the listed screens objectively evaluated under the same standards is invaluable in assessing how the screens might work in my environment. Thank you for recognizing the critical need for this area of review. This is, by far, the best and most complete review of ALR screens. Keep up the great work!

Posted Mar 4, 2016 2:59 PM

By Matt Frazer

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Thank you so much for posting this extensive review of ALR screens, I have never seen anyone undertake this task and you should be comended for the effort. I currently use a Carl's place DIY ALR screen that I bought on a whim to replace my painted wall (following the projector central instructions when it was painted). I noticed a signifigant improvement in my tightly packed dedicated theater since the room is under 10 feet wide and I get light polution reflecting from the walls. It would be interesting to get this screen added since it is so cheap, to see if it can hang with these other options... Although after this whale of a test I wouldn't blame you if you never want to see another ALR again. Keep up the great work, it's reviews like these that keep me coming back.

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