2020 Guide to Projector Technology Terms

2020-Guide-to-Projector-Technology-Terms

Brightness Related Terms

Today’s projectors are brighter than ever and that means that ambient light isn’t the problem it was a decade ago. Even inexpensive projectors for K-12 schools can deliver 3,000 – 4,000+ lumens. That’s three times the brightness produced by the average education projectors from just a few years back.

Most projectors on the market are bright enough for an 80″ diagonal screen, the size commonly found in a typical classroom, conference room, or training room even with all the fluorescent room lighting on. At the worst, the presenter might have to turn off half the bank of lights to improve visibility. If there isn’t direct sunlight striking the screen, most modern education projectors should be bright enough to do the job in a typical K-12 classroom.

The larger spaces like a 100+ seat university lecture hall will require a bigger, brighter, and more expensive projector. A quality 4,000 lumen projector with a high-color lumen output should be bright enough for typical large lecture halls, but brighter 5,000 to 8,000 lumens might serve this application better. In this report, we refer to very bright, more capable projectors typically as either Higher Education or High-End projectors.

Even though you may not need a very bright projector, let’s look at the reasons to step up to a brighter projector. One big advantage of spending more at the beginning for a brighter projector is that you can run it in eco-mode, ultimately saving money by increasing lamp life. While the savings isn’t as dramatic there is also a benefit to running a laser projector in ECO because it can extend the life of its laser light engine by several years as well. The result of not having to change out bulbs could save money and time in the long run.

Your K-12 school might have the funding from technology grants to purchase the hardware initially, but money for routine maintenance, including replacement lamps might be scarce.

ANSI Lumens

The industry standard for measuring brightness is ANSI lumens. When rated brightness is listed in anything but ANSI lumens, it is pretty much a meaningless number especially when trying to compare projectors from different manufacturers.

Sometimes manufacturer may rate brightness in other ways like Lux, ISO Lumens, Peak Lumens etc. Since these are not a universal standard of measurement, these proprietary ratings can’t be used to compare brightness between projectors from different manufacturers. It might be helpful when comparing two “LUX” rated models in a manufacturer’s own lineup, but this spec can’t be used to compare brightness with another manufacturer’s projector.

For each projector we review, we measure brightest mode at full wide angle – this is with the iris wide open, so the most amount of light gets through. We take 3-4 readings at about 15-20% out from the center of the lens. That should give a pretty good approximation of ANSI lumens unless a projector’s brightness rolls off excessively at the edges, meaning the image is brighter in the center of the screen

For the rest of the modes, we measure them at mid-zoom, so the iris is closed halfway. This is because it is more common for a projector to be zoomed in a bit than installed at full wide angle.

For some interchangeable lens projectors, max brightness might vary depending on th e lens utilized. Once a lens is detected, the projector may adjust its maximum brightness level. For example, below is a chart from Epson for their Pro L1755UNL projector.

Epson-Pro-L-Series-Lenses

While brightness is important, it should never be the sole consideration when designing a projection system. There are other factors such as type of screen material, ambient light in the room, and several other factors that may affect the perceived brightness and clarity of the projection image.

Ambient Light

Ambient light is a term that refers to the amount of light that is present within a room environment, which interferes with the contrast of the projector. That is light coming in from windows, or overhead lights that cannot be dimmed or turned off, resulting in the “washing out” of the projected image. For rooms with uncontrollable ambient light, such as most classrooms, conference rooms, and museums, there is a workaround: Ambient Light Rejecting Screens.

Ambient Light Rejecting Screen

Ambient Light Rejecting screens started becoming popular less than a decade ago, and for good reason. They allow users to be able to project in rooms with a respectable amount of ambient light, filling a large screen with far less loss of contrast and color saturation than with traditional screens. This screen type, combined with far brighter projectors, has taken projectors out of darkened rooms and into the light. Whether in a classroom or auditorium, no longer does the room have to be made dark!

From a practical standpoint that gives projectors a significant advantage over very large monitors in most environments. That’s because large monitors are still relatively small as they are only “affordable” up to about 71”-80”. A 100” monitor setup can easily cost 10 times that of a 100” projector and screen setup of really good quality.

In a perfect world, that means that using a projector with an ALR screen will “reject” ambient light from the room producing an image about as good as if there was no ambient light in the room. That, however, is to assume that the ambient light is not coming from near where the projector is positioned. Today (2020) fixed ALR type screens from recognized brands sell starting at under $1000 for a 100” size, while premium brands can cost twice that or more.

The least expensive projector in a bright room, with a good ALR screen can outperform other projectors costing far more, but with traditional screens.
The least expensive projector in a bright room, with a good ALR screen can outperform other projectors costing far more, but with traditional screens.

Now a 3,000 lumen, standard throw projector in a fairly bright room using a 100” ALR screen may look a lot better than a 5,000, or even a 10,000 lumen projector on a regular screen. In a darkened room, of course, the brighter projectors will look much brighter. But, the least expensive projector in a bright room, with a good ALR screen can outperform other projectors costing far more, but with traditional screens.

There’s always a catch! In this case, two of them!

  1. To be effective at rejecting ambient light, that ambient light can’t be coming from anywhere near where the projector is placed.
  2. Ultra Short Throw projectors require special ALR screens specifically designed for UST.

With a great ALR screen, a projector ceiling mounted 12 feet back from a 100” screen (typical), ambient light coming from unshaded windows on either side of the screen will have almost zero effect on how the projected image looks. Close shades on those windows and leave the rest of the room the same, and you probably can’t tell the difference looking at the projected image. But, if those windows are in the back of the room, behind the projector, the ALR screen can do nothing, for to reject that ambient light it would have to also reject the light from the projector!

If the light is coming in from a back corner, then the ALR screen should still be pretty effective, and more so the further the ambient light is to the side. The same is true for overhead lights.  Ambient light from almost directly above the screen will be rejected, but if that light is closer to the projector – again, it can’t be.

Screen Innovations 100” Solo screen is an ALR type designed for UST projectors.  Shown here at CEDIA, under lots of trade show ambient light.  The projector an Epson LS500. Vibrant colors!
Screen Innovations 100” Solo screen is an ALR type designed for UST projectors. Shown here at CEDIA, under lots of trade show ambient light. The projector an Epson LS500. Vibrant colors!

Ultra short throw projectors cannot use an ALR screen designed for standard throw projectors, as those screens mistake the light from the projector as ambient light. This results in a completely washed out image. For this reason, if you’re pairing an ultra short throw projector with an ALR screen, you must choose one that is specifically designed for a UST projector.

Epson Laser TV

ALR screens can be game changers in many business and education environments. In today’s newer classrooms, more emphasis is being made on having natural light – skylights where possible, and more windows. ALR screens can make a huge difference in these environments. An ALR screen can make a 100” screen fully readable in a conference room with a wall of glass on one side, without spending a fortune on a massively powerful projector. In most situations, ALR screens are the way to go.

In addition to classrooms, ALR screens are ideal for conference rooms, auditoriums, and museums – anywhere where lighting cannot be completely controlled and minimized. They can be a game changer in brighter rooms, requiring far less to be spent on buying a higher power projector.

As more motorized ALR screens hit the market, I would expect this technology to dominate the market. I predict they will be used in most classrooms and conference rooms as the price points will drop, and they won’t cost that much more than a standard screen. If a good ALR screen only adds $500 or so to the budget, but it saves you $1,500 by going with a less bright projector (and still having a better-looking image), they certainly will dominate the business and education world.

Resolution Related Terms

Resolution is a term that refers to the number of horizontal and verticle pixels of the projected image. The higher the number of pixels, the higher the resolution, and the sharper the image.

Common resolutions found on projectors:

Type Resolution Aspect Ratio
SVGA* 800 x 600 4:3
WVGA* 853 x 480 16:9
XGA 1024 x 768 4:3
WXGA 1280 x 800 16:10
WUXGA 1920 x 1200 16:10
720p 1280 x 720 16:9
1080p 1920 x 1080 16:9
4K UHD 3840 x 2160 16:9

* SVGA and WVGA are essentially “legacy” resolutions.

While there are still some very low cost projectors sold with SVGA an WVGA resolutions (including some “toy” priced dim LED pico projectors for home), but they are no longer normally bought by schools. There are still large numbers of them in K-12 schools. Most are long overdue for replacement. Their bulbs last only a fraction of the life of new projectors (nevermind laser projectors), so the cost of supporting those old projectors is high.

XGA models are typically used to replace the SVGA (and if any are still around – VGA) projectors. SVGA projectors are typically replaced by WXGA, WUXGA or 1080p projectors.

HD vs Pixel Shifting vs Native 4K

Most pixel shifting projectors can accept up to a 4K signal. While pixel shifting can’t match the resolution of a true 4K projector, it does increase sharpness and detail compared to a standard 2K projector. When fed 4K content, the projector uses pixel shifting to fine tune the image to more closely resemble 4K. Pixel shifting fires each pixel twice by shifting the location by 1/2 pixel diagonally. Combined with good image processing, pixel shifting can do a very nice job emulating the original 4K content.

The images above show the noticeable improvement pixel shifting provides when viewing 2K and 4K content. The images above are screenshots of projected 4K material. The first images are close ups showing the same image with Pixel Shifting Off and On. They really highlight how much this feature increases the clarity and detail of a WUXGA projector.

When viewed in person, the actual differences on the screen are greater than what you are seeing on this site. This is because of the heavy compression and scaling of the images for the web, so the differences you are seeing when viewing it on this website will be less noticeable. As you can see in the above images, when you compare 4K content with pixel shifting turned on and off, the difference is impressive.

Small type and fine details that can’t be discerned on a basic 2K – WUXGA (or 1,080p) projector can often be resolved with pixel shifting. It is enough to make a real readability difference on CAD, engineering, and scientific drawings, renderings, or anything else demanding max detail.

It is only when you do a side-by-side comparison between a true 4K projector versus a 2K pixel shifting projector that the resolution difference is noticeable. The images below show the visible resolution difference between a native 4K projector and a projector utilizing pixel shifting when displaying native 4K content.

Since the projector’s native resolution is approximately 2.3 MP, it won’t be as sharp/detailed as a true 4K projector (8,8 MP resolution). While a Pixel Shifting HD projector does deliver more clarity, it still can’t match the resolution provided by a native 4K projector.

Pixel Shifting also requires a lot of processing so it can’t be combined with some features like edge blending and Creative Frame Interpolation  but even some more basic things, including some types of noise reduction cannot be utilized.

So how do I choose between a pixel shifting projector and a true 4K projector? To make a wise decision you must factor in your budget, what you are watching, and from where you are watching it.

True 4K high lumens projectors cost at least four to five times as much as their 2K counterparts. Consider this, an 8,000 lumen true 4K laser projector can retail for $60,000 while an Epson pixel shifting 16,000 lumen 2K laser projector costs about 1/3 of that amount. This will be true until we see dramatic price drops in the true native 4K projectors to make them more price competitive. True 4K projectors are going to be hard to justify in most situations even when 4K content will be used.

In many situations, the content lacks the detail required and is viewed at a distance where the difference between 4K and pixel shifting cannot be perceived. While pixel shifting can’t match the resolution of a true 4K projector, it does increase sharpness and detail compared to a standard 2K projector.

So, if the image is going to be viewed from fairly far away, a brighter, less expensive pixel shifting projector might be a better option. In many situations the benefit of extra brightness far exceeds the benefits of additional resolution.

Equivalent Visibility Rule

The Equivalent Visibility Rule is used to determine how large a display size is needed when teaching or “presenting” to a group, regardless of the number of those attending the class or meeting. It is more effective today than the old 4/6/8 rule long used for determining how large a projection screen or monitor is needed, in a room.

Background: No longer do we primarily present to the classroom or conference room with presentation software such as PowerPoint. Or, rather we still do, however, today we are also electronically displaying emails, websites, spreadsheets, documents, engineering drawings, art work, and much more.

4/6/8 (without getting into it) is an old “A/V” rule that was good for figuring out if the person in the back of the room can follow a presentation using typical large type (30, 36, 48, and 60 point). But, it doesn’t work well when you need that person to be able to read the numbers on a spreadsheet.

Essentially, the Equivalent Visibility Rule answers this problem.  Given that people work with spreadsheets, docs, detailed drawings, etc. normally their desks, and can read all that content without trouble, then if those people typically have about a 21” monitor on their desk and sit about 28” back, how large a display would be needed for a person sitting 10 or 12, or 30 feet from the display?

You may be surprised.  If the person furthest back in the room is 15 feet from the screen or display, then to read all that small type – the screen should be (drumroll…) at least 100” diagonal. And ideally between 120” and 150”.

For more information, on the Equivalent Visibility Rule and why its decision makers should take heed, here’s a more in depth feature.  (link to it when written).