When shopping for a video projector, there are a few main specifications you need to look for. Many of these are unique to projectors, while some also apply to flat-panel TVs.
The single most important number to look for is the lumens, or brightness, measurement. A lumen is a measurement of how much light a projector can produce. This will determine what screen size you can use with it. For example, a pico projector with 100 lumens will limit you to a 40-inch screen, while 10,000 lumens is bright enough to fill a screen at your local movie theater.
What to look for depends on both your screen size and the light engine of the projector. LED and laser projectors might produce only 1,300 lumens, but that will be plenty for a 120-inch screen in a home theater. If a projector is rated at 1,300 lumens, the projector bulb might grow too dim after a few hundred hours of shooting images onto the same screen. Having too many lumens isn’t usually an issue with a projector, as there are ways to handle this. But too few (shoot for at least 1,300 lumens) can become an issue that you cannot usually improve. You should determine what size of screen you want, then choose a projector that’s twice as powerful as you need to allow enough headroom for calibration and bulb aging.
THX Certified Projectors: Close to Perfection
If you’re willing to spend at least $3,000, a THX-certified projector is the cat’s meow. The important image parameters will be already set at the factory to provide an image close to reference without a calibration. However, you might expect your home systems integrator to still do some fine-tuning to minimize any rendering of the image by the color and texture of the projection screen.
A THX projector’s ISFccc (Imaging Science Foundation Certified Calibration Configuration) logo signifies that the projector incorporates the necessary controls to enable a professional calibrator (a qualified home systems integrator should be able to do this, too) to adjust the projector while locking and protecting the settings. The image from a projector is affected by the age of the lamp, the type of screen, and the room itself. While THX presets and screen offsets can get a projector to be more accurate, a calibration is the only way to be certain it is accurate. Without ISFccc controls, a home systems integrator might not have all the tools he or she needs to produce an ideal image from a projector.
Today, almost all home theater projectors have a resolution of at least 1080p, and you can find them for less than $1,000. Starting to appear on the home theater scene are 4K projectors, which offer resolutions of 4,096×2,016 or 3,840×2,160 instead of the standard 1,920×1,080. The most affordable ones start at $10,000 and move up to $25,000 and beyond. A new feature some of these higher-end projectors may incorporate is “pixel shifting,” which boosts the resolution of a 1080p projector. Video projectors with pixel shifting use 1080p panels but have a lens mechanism to shift the panel by half a pixel vertically and horizontally. This eliminates the tiny gaps between pixels and can seem to improve detail. It isn’t true 4K, but the projector can accept a 4K signal to try to produce an image that is sharper than 1080p.
A projector’s aspect ratio refers to the ratio between the width and height of the image it produces. A 16:9 aspect ratio is one of the most commonly employed by projectors, and is the standard HDTV, or 1080p, format. This will produce an image that is 16 units in width for every 9 units in height. Movies are being shot that can be reproduced by projectors in a wider anamorphic (also called CinemaScope or 21.9) format. For the best viewing experience, the shape of the screen should be the same as the projector’s native aspect ratio, although there are projectors available that include automated lens memory systems that can zoom and shift the image to fill as much of the screen as possible. Combined with a masking system (black fabric that rolls over portions of the screen to alter its shape to fit the format of the projected image), you get the movie in its original format and as large as possible. Many systems offer up to 10 lens memory settings, enough to handle all of the major aspect ratios (1.33:1, 1.78:1, 1.85:1, and 2.39:1). Just like at the theater, everything can automatically adjust to provide the most immersive experience. A few select projectors offer a native 2560×1080 resolution for CinemaScope (21.9) films. With this type of projector, films will always occupy the center of the screen, and no external hardware or lens memory is necessary. Only DLP projectors are available in a native 21:9 aspect ratio, so your options are more limited than projectors with lens shifting capabilities.
No number is as important to image quality as the contrast ratio. This is a ratio that compares the brightest whites a projector can produce to the darkest blacks. The higher the number the better the contrast ratio is and the more dynamic the image. Often, these numbers are inflated, so the key is to look at the contrast ratio number that is native, not dynamic.
You can enhance the contrast ratio with the use of a lens iris. An iris lets you reduce the amount of light that a projector can display. Since having an image that is too bright can cause eye strain, the iris lets you produce an ideal image. As the bulb in your projector ages (not an issue for bulb-less laser and LED projectors) and produces less light, you can open up the iris to allow the projector to deliver more light to the screen. Closing the iris to the optimal level also produces darker blacks, since less light is able to leak out during dark scenes.
Some projectors have an automatic iris, which will open during bright scenes and close during dark scenes. This produces higher dynamic contrast numbers by making bright scenes brighter and the dark scenes dimmer. In some cases this works well and lets you see more shadow details while not making the highlights dull. In other cases this dynamic iris action is visible when you move between scenes and you see the image change brightness as you watch. The performance of dynamic irises improves every year, with some projectors now able to transition more smoothly and seamlessly.