Holiday 2012: Projectors

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A home theater is most like a movie theater when there’s a projector in the room. Even with flat-panel TV sizes growing, if you want a diagonal measured in three digits, you need to project the picture at some distance from the screen. The key to a 100-plus-inch picture is matching the right type of projector to the room you call a home theater.

What is a home-theater projector?

Essentially, it’s a box that uses a bright light and lens to magnify a postage-stamp-sized electronic matrix into a projected picture. Inputs let you attach such video sources as a Blu-ray Disc player, computer, games console or cable/satellite tuner/DVR.

When is a projector not a home-theater projector?

When it fits in a pocket or you can’t get it in the door. In the former case, the emerging pico projector category simply doesn’t produce sufficient brightness to compete in the same league as a tabletop projector. In the latter case, a projector meant for a commercial movie theater would be overkill for living-room use.

 

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How do home theater projector technologies vary?

Home projectors generally fall into one of three categories: transmissive LCD, reflective LCD and DLP.  With a conventional LCD projector, light passes through a trio of micro LCD panels, each layer with a filter representing one of the three primary colors. (This is sometimes referred to as 3LCD technology.) With reflective LCD—also called Liquid Crystal on Silicon or LCoS and by such brand names as Sony’s Silicon X-tal Reflective Display (SXRD) and JVC’s Direct-drive Image Light Amplifier (D-ILA)—light bounces off a chip-sized matrix of LCDs that twist to reflect or absorb light. With a Digital Light Processor, a micro mirror array invented by Texas Instruments, tiny hinged mirrors pivot to reflect light as if a bleacher filled with fans flip plaques to compose a larger sign.

In all these cases, the primary image-making element inside the projector is not unlike the grid of pixels displayed across a flat-screen TV. But instead, the matrix is miniaturized many thousands of times. It will take a high-powered lamp, sometimes a spinning color wheel and a lens that magnifies and focuses the image to project an enlargement. Optics in a projector work the opposite way of a photo lens. In a camera, the lens gathers external light and focuses the image onto a tiny sensor chip. In a projector, the lens takes the image from the minuscule chip and passes the light out to a surface many times larger.

How much brightness do I need?

Projector brightness is measured in American National Standards Institute (ANSI) lumens. Home-theater projectors range from about 1,000 to 10,000 lumens. Assuming you’ll be projecting in near darkness, figure 1000 to 2000 lumens for a 60- to 80-inch image, 2500 to 3500 lumens for an 80- to 120-inch picture and more than 3500 lumens to fill screens greater than 120 inches. Projecting in total darkness lets you get by with a model rated at fewer lumens, but unless you live in a cave, shutting out all ambient light may not be practical.

How much resolution should I get?

The most you can get, since one or two million pixels spread out will be more noticeable than the same pixel count scrunched together on a flat-screen HDTV set. Full HD (1920 x 1080p) is the best choice, but you can save some money with a 720p projector. (Also, if you’re planning to project sports from ESPN, ABC or Fox, 720p matches the native resolution of those networks anyway.) Higher computer-compatible resolutions are typically given as XGA (1074 x 768), WXGA (1280 x 768) or greater.

What about inputs?

A multimedia projector offers a variety of inputs. To deliver high-definition video from a cable box, satellite receiver or Blu-ray Disc player or an up-converted signal from a DVD player, your first choice is always an HDMI input. Depending on the types of devices you plan to connect, you may also want a set of component video inputs, VGA (also referred to as a PC, analog RGB or D-sub) and composite video.

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What special features might I find interesting?

3D technology is suddenly the rage among home theater projector enthusiasts. Top projector companies like Optoma and Epson are creating projectors with 3D technology. Basically, 3D (three-dimensional) technology uses two overlapping images to “trick” the eyes (and more importantly, your brain) into seeing two different images—one for the left eye and one for the right. Using specially designed cameras, the content for 3D movies is separated horizontally so that one eye sees an image farther back, and another eye sees an image that is pushed forward, seemingly off the screen.

Anaglyph technology is the most commonly used method for implementing 3D. This is the technology that tints everything on the screen in either cyan or red. The corresponding glasses, cheaply made cardboard lenses tinted cyan and red, force your eyes into the illusion of depth. Anaglyph technology is cheap to produce (since it requires no special equipment to use, it can be viewed on your regular home TV or projector) and the glasses (also referred to as Passive Glasses) are inexpensive to manufacture, which makes it the most widely available technology for 3D today. One disadvantage to using passive glasses is the range of color. Since it is tinted for effect, you will not see natural color tones as true as you would without the glasses.

Some home theater projectors use another type of glasses, which are more expensive because the glasses house miniature electronics to achieve the 3D effect. These are known as Shutter Glasses (also known as Active Glasses or Active LCD Shutter Glasses). These glasses rely on the TV or home projector to project left/right images as fast as 120 frames per second. The glasses then actively block the left or right eye, creating a sense of depth. One disadvantage to Shutter Glasses is the fact that because of the delicate electronics involved, they are expensive, and projectors usually only come with two pairs of glasses included. Parties or larger families have to consider the expense of equipping everyone for the ultimate 3D experience. But it does look like 3D is here to stay. Many HDTV sets and home theater projectors are being sold as 3D units—and many more movies are being released for home use with 3D technology enabled.

Another special feature for home projectors is connectivity. If you’re a photographer who gives slide shows, some projectors include a USB port for playing JPEG images directly from your plugged-in media. Some projectors contain Ethernet ports, but capabilities vary since the connection may be just for control, while others can stream video over a LAN from a computer or the Internet and some may be able to mirror the presentation on the big screen to the computer screens of students in a classroom.

What about sound?

Most projectors either have no audio capability or a low-power mono speaker that should be used only if your video source isn’t connected to a home theater sound system. A big picture demands big sound, so don’t scrimp on the speaker system. However, there are some all-in-one portable projectors with a disc player, stereo speakers and a handle, but they’re meant less for use in a permanent home theater than for an all-purpose room accommodating an impromptu movie or sports event. Also, attached to a heavy-duty extension cord, these projectors are great to set up outdoors on a summer night. A flat, white garage door or bed sheet can stand in when you can’t bring out a real screen.

Should I invest in a screen?

A white wall may already be in place, but it’s not the ideal surface for an audience to focus its eyes upon. If you’re installing a projector, you should also mount a screen. Sizes vary. Screens, some with motors, can be hidden until needed, or a free-standing screen with a stand and easy setup can be retrieved from the closet.

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What is the keystone effect and how can I correct it?

If the projector is positioned off-center from the screen, you may notice that the geometry of the projected image is decidedly more trapezoidal than rectangular. This distortion is known as the keystone effect, also called the tombstone effect. Better projectors can be adjusted to compensate for the effect, a feature referred to as keystone correction or keystoning. Without keystone correction, you’re left to your own ingenuity to reshape the boundaries of the image—such as moving the projector left or right or piling books underneath. Keystoning is a menu-driven digital process in which the number of pixels is reduced, so the tradeoff for squaring off the picture can result in somewhat lower resolution.


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How often will I have to replace the lamp?

Estimated lamp life is listed with each projector model, but typical longevity is 3,000 hours. Conventional mercury lamps dim over time and burn out. (Letting the projector cool off before moving it can help extend bulb life.) Replacement cost can be several hundred dollars. Since lamps vary in size, it’s important to order the right lamp for your model. Getting a backup lamp when you order a new projector is prudent. Some new projectors use LEDs, which last the lifetime of the projector. Such models may cost more initially, but they can save money over time by eliminating recurring lamp replacement costs.

What are the benefits and limitations of a pocket (aka pico) projector?

Because these tiny projectors use an LED for the light source, the lamp lasts the life of the projector. Also, since the projector isn’t much larger than an iPhone, you won’t think twice about taking it with you. Enlarging photos, video or other visual content from a media-playing phone, portable DVD player, netbook or notebook can be a real “crowd” pleaser, versus crowding around a small screen. But make sure you appreciate that these projectors are meant for personal use or a handful of people in an extremely dark room. The lumens put out by these projectors are a fraction of what you get from even a modest tabletop projector. They’re not designed to complete with room light and they’re most effective when keeping the image under 30 or 40 inches.

If you’re shopping for a pico projector, make sure that it comes with the type of input or inputs you require or that there’s an optional adapter cable available for connecting the particular device you have in mind. (An iPod, computer and portable DVD player use different types of video outputs.) Some pico projectors may include a card slot or USB input and play particular formats on their own.

Can I mount a projector from the ceiling?

Yes, and it’s probably the best spot in the room to place it, since ceiling projection doesn’t interfere with seating, popcorn dispensing or lines of sight. The main concern is whether you or an installer can run wires to connecting equipment and electricity. Though the projector may be hanging upside down, the picture can be correctly upturned in the setup menu. Projector ceiling mounts are available from the same manufacturers who make wall mounts for flat-panel TVs.

The Takeaway

  • If you want a truly big picture, you need a home-theater projector.
  • The larger the image, the more brightness (measured in thousands of lumens) you need. The less you’re able or willing to control ambient light in the home theater room, the more projected brightness you need to compete.
  • Since high-definition resolution is best appreciated on a big screen, you shouldn’t settle for anything less than an HD projector.
  • Having a variety of input types on the projector makes it more versatile for connecting different video sources.

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I work for a projector rental company, and was wondering what some good ways are to fix the "keystone effect", other than using books? I appreciate it, thanks!

Hello,

The way you would eliminate “Key Stoning” would be to center a projector to the middle of the screen being used. Some projectors have a built in key stone correction which can make minor corrections. In most cases, the screen is higher than the projector so the simple solution is to raise the projector and not tilt it upwards.

The height of Stand Master 11 is adjustable in a continuous movement using a crank. Features two sturdy wheels for easy moving from location to location.

I'm an AV tech. Some tripod portable screens have an anti-keystone feature. A metal bar is hidden at the top of the centre post and you pull it straight up then lean it over 45 degrees. You can then hang the screen on any of the notches on the bar to angle the screen towards the projector.