Some of life's purchase decisions can result in sleepless nights: A new car, a new house, a cruise vacation, and a kitchen remodeling job are just a few examples. Yet, we manage to get through them because we do the research and legwork required to make an informed purchase decision. We know the benefits and drawbacks, and try to uncover as many hidden costs as possible. We may not always be 100% satisfied with the outcome, but at least we know what we're getting into.
Purchasing a new video projector doesn't seem to belong at that level of angst. Yet, for many folks, this decision can create just as much worry and confusion: How many lumens do I need? Is it time to go widescreen and, if so, which format? How many digital connections do I need? How often will I have to relamp, and what do the lamps cost me? Who has the best warranty? Which imaging technology should I use? How about interchangeable lenses? Is lens shift important, or is digital keystone correction good enough?
It's Been A Few Years, Eh?
Projection technology has advanced by leaps and bounds in the past decade. Prices have plummeted, resolution has soared, and all of those old familiar analog signal interfaces are fading away, replaced by digital inputs and outputs.
Now would probably be a good time to point out that the term “video projector” is basically obsolete. All projectors can show video, and a growing number of projectors support at least one HDTV format (1280x720p) natively.
That's because projectors—like consumer TV sets—are all expanding, moving to widescreen formats. Yes, you will still find 4x3 XGA (1024x768) models out there, but everyone wants widescreen. All new notebook and tablet computers are widescreen, with the notable exception being Apple's iPad 3. But even that product plays video back at 720p HD resolution.
So what you want is simply a new projector. What you'll want to focus on more closely is what resolution and aspect ratio you need to support.
The most common widescreen aspect ratio is 16:9, or 1.77:1 to be exact. This is the screen height and width for 720p and 1080i/p video content. The thing is, 1280x720 and 1920x1080 are video formats, not computer display resolutions. Examples of the latter would include 1280x800 (Wide XGA), 1366x768 (also Wide XGA), 1680x1050 (Mac), and 1920x1200 (Mac, WUXGA).
Note that most of these computer resolutions have a slightly different aspect ratio: 16:10. While we're probably in agreement that widescreen is the way to go, the question is—which ratio? Is it 16:9 or 16:10? (And while I'm on the subject, let's all agree to stop using XGA in 2012, OK?)
Here's the rub. If you are showing 16:9 video on a 16:10 screen, you'll have unused, thin, black “letterboxed” bars running horizontally across the top and bottom of the projected image. But if you try to project 16:10 graphics on a 16:9 screen, you'll wind up with thin, “pillarboxed,” vertical black bars at the left and right edge of the screen.
There's no easy answer here, except that you should pick the projection aspect ratio that matches a majority of your projection needs. If that is playback of live and recorded media video content, then go 16:9 and format your PowerPoint and other graphics to the same aspect ratio.
Light Me Up
The next question concerns how much brightness you'll need. The fact is, it takes a lot of horsepower to overcome relatively low levels of ambient light and still produce “contrasty” images on a projection screen.
A better question might involve just how bright you want the images to appear on screen. The SMPTE luminance target for motion picture screens is about 16 foot-Lamberts, but to get that from a large screen—say, 20-feet wide—requires about 3,500 lumens to start with. And the SMPTE specification is for a darkened room.
In your case, you may need 2x or even 3x that level of brightness to overcome ambient light spill. Let's say you are showing IMAG video on a 16x9, 12 foot wide projection screen with unity gain (1.0), and you need about 60 foot-Lamberts for a bright enough image under full lighting.
Doing the math, that 16x9 screen measures 6.75 feet tall by 12 feet wide, for a total of 81 square feet. To calculate the required lumens, multiply 60 (ft-L) by 81 (ft2) and you wind up with 4,860. So 5,000 lumens is the minimum for your application.
If you plan on using long projection throws and long-throw lenses, that number's gotta go up as these lenses have smaller apertures and pass less light. Projector manufacturers should be able to give you the aperture ratio for a given lens so you can calculate the decrease in screen brightness and make up for it (possibly with higher-gain screens).
Focusing In
Speaking of lenses, which type should you use—fixed? Interchangeable? Zoom lenses? It all depends on the application. If your projector is going to be installed and never moves, always go with a prime (fixed-focus) lens, or one with limited zoom range to maximize the photons hitting the screen.
There's no reason to select very long focal lengths if you are installing both screen and projector. Remember that most zoom lenses exhibit maximum optical sharpness and minimum geometrical distortion near the center of their focal range, not at the ends.
If your projection throw calculations are leading you into zoom ranges of 3:1 or longer, then upgrade to a larger screen. Try to keep zoom ratios under 3:1 for maximum brightness and optical crispness. Example: That 6.75 foot x 12 foot 16:9 screen mentioned earlier is mounted at a distance of 40 feet from the projector, calling for a 3.3:1 projection throw ratio.
By selecting a 9 x 16-foot screen instead, the throw ratio drops to 2.5:1, which is generally a less costly lens selection and one with a wider (faster) aperture. In addition, 1:2.5 lenses are usually in the range of f2.0, or about ½ f-stop dimmer (25%) than a 1.8:1 short-zoom lens.
In contrast, an f 3.0 – 5.0 lens will have an effective aperture in the 2.5 – 3.0 range, which is a full f-stop (50%) dimmer, and you'll pay a lot more for the lens that you will for the screen.
The Shift Is On
Speaking of lenses, more projectors in all classes are equipped with some sort of mechanical lens shift. It could be as simple as vertical shift, or it could also include horizontal shift.
The advantages of lens shift are obvious: You don't have to mount the projector perfectly square to the screen, with images optically centered. If the projector installation calculations are a little off or the screen isn't mounted exactly where you wanted it, no sweat—just adjust the X/Y knobs and move the image accordingly.
Lens shift is vastly superior to the digital keystone correction option that most projectors offer. Digital keystone correction simply re-maps the image to get the tilt out, but sacrifices resolution by doing so (and on lower-resolution projectors, introduces “jaggie” picture artifacts to images).
Lens shift does it the right way, just like an old view camera: It moves the rear lens element relative to the imaging device, shifting the position of the projected image without distorting it.
Most installations only need vertical lens shift, since it's much easier to get the centerline of the lens aligned in the horizontal plane of the screen. But having both is nice, especially if you have to change out a lens.
As for projectors with built-in vertical lens offset—usually DLP projectors—keep in mind these are intended for inverted, ceiling-mount applications. That limits their usefulness considerably, especially for portable, temporary applications.
Hook Me Up
Pay careful attention to the connector complement on your new projector. Analog signal interfaces are on the decline, while digital interfaces like HDMI are de rigueur now. Even the 10-year-old DVI interface is on its way to retirement, to be replaced by DisplayPort in the next few years.
For any installation projector, you should have at least one if not more digital display inputs (HDMI and or DVI), plus a USB port (useful for software upgrades and automatic playback of certain file formats) and an Ethernet connection (for remote operation and diagnostics).
Computer manufacturer support for the 15-pin VGA jack is phasing out this year. Newer notebooks and ultrabooks will only offer DisplayPort and/or HDMI, and you'll need adapters to use MacBooks, iPads, and other tablets with VGA. Might as well start using HDMI and DVI.
Here's another compelling reason to go digital: Analog video connections are fast disappearing from DVD and Blu-ray players. Current-model Blu-ray players offer only an HDMI output jack and a composite (480i) analog video jack.
What's more, copy-protected content played back through DVD and Blu-ray players, as well as set-top boxes and game consoles, can disable existing analog component video connections. So you can't even rely on older Blu-ray or DVD players to do the job.
The Buy-In
The good news about projectors these days is that they are very affordable. You should have no trouble finding a 2,500-lumens “hang and bang” or desktop projector with wide XGA (1280x800) resolution for $2,000 or less. A 4,000-lumen model for a larger room will set you back about $2,000 to $3,000, while you can pick up a 6,000-lumen “do everything” model with interchangeable lenses and lens shift for $6,0000-$8,000.
How you choose to amortize your purchase is up to you. Make sure to build several lamp changes into the total cost, as you'll have to swap those out every 1,500-2,000 hours or so. Depending on the projector's brightness, you'll spend $200 to $400 for each lamp change. Example: If you buy a 4,000-lumen projector and re-lamp it once a year (let's say after 1,500 hours of operation), add another $300 for each year of operating cost. Over five years, that's $1,500 on top of your original purchase.
Or, you could look into the new lampless projectors coming into the market from BenQ, Casio, and others. These models are already at 3,000 lumens and climbing, and the latest versions support wide XGA resolution.
Projector technology (aside from lampless LED and hybrid designs) isn't moving at the jack-rabbit pace it used to. Pricing seems to be the big issue these days, even more so with the growing threat from large 70- and 80-inch LCD screens that are replacing projector installs in smaller rooms.
Even so, you should figure on getting at least three to five years out of your purchase, after which you will probably want to upgrade just to stay on top of advancements in connectivity, lamps and illumination sources, and the slow but inevitable move to higher resolution imaging.
Conclusion
Back in the 1990s when LCD and DLP projectors burst onto the scene, they came at a substantial cost ($8,000-$10,000) and weren't all that bright (500 lumens) with low resolution (VGA, 640x480). And they were heavy (20–30 pounds).
Today, you can get four times the brightness, twice the resolution, better optics, digital interfaces, Ethernet connectivity, compact profiles, lighter weight, and lens shift; all for 20%-25% of the 1990s pricing. It's hard to go wrong.
Even so, do your homework. There are plenty of projector guide websites that are ready to help you, like projectorcentral.com. Figure out your total cost of ownership, including lamp changes, and come up with a realistic amortization schedule (three to five years).
Make sure you have enough digital video inputs. USB ports are also handy, as are Ethernet connections for remote monitoring. Lens shift is a plus and will make your life easier. And by all means, go widescreen—there's no reason to sit on the sidelines any more.
PETE PUTMAN heads ROAM Consulting LLC based in Doylestown, Pa. In addition, Putman maintains HDTVexpert.com, a popular website that covers digital TV, HDTV, and display technologies.
