Size Matters: Large-Screen Digital ProjectorsJuly 17, 2006 | Jim Moulton
In Edutopia video segments, you often see teachers and students using a television in place of a computer monitor to provide better access to visual information. The reasons for using the television instead of the monitor are pretty straightforward: The television has a larger screen, and it can be placed higher so that there are no "bad seats."
Though the use of a television is one way to improve the view for your students, it is not enough, and there are other ways that provide even greater access to all. Let's take a look at large-screen projection.
Why Is a Big-Screen View So Important?
Put yourself in your students' place. Imagine going to a professional-development session where the presenter is sharing a Web-based resource that would meet a critical need in your classroom. You are really interested, and hungry for the knowledge. But the only screen available is the presenter's laptop, and though it has a nice 15-inch or even 17-inch screen, there are twenty-four other participants in the room, and you happen to be sitting toward the back. That means that as everyone leans toward the screen in order to see this great utility, your view is blocked completely.
The presenter could regain order, and establish equity, by turning the screen away from the audience and using words to describe what he wants you all to see, but that would leave everyone frustrated. Perhaps he could stop presenting and give everyone time to file past the screen in order to see and try out the Web site, but that would cause too much commotion and seriously interrupt the pace of his delivery. Or, if he was better prepared, he could pass out printed screen shots of what you would have seen if you could view the Web resource live.
None of these solutions is optimal, and, truth be told, chances are that he would carry on, knowing that only a few will really see and experience what was intended as information for all. And those few will be limited to folks who are either lucky enough to be sitting front and center or aggressive enough to force their way into a position where they can see. Probably this is not what you want to see happening in your classroom when a school from far, far away responds to one of your postings, and you want everyone to share in the excitement and to get the same information.
So, How Big Is Big?
The television screens teachers use in the Edutopia video segments are certainly larger than those of traditional computer monitors, and their placement makes them more visible. But imagine there was a television screen -- say, one that was 32 inches (measured diagonally) -- in that professional-development session. That's not a bad size, but the screen measures 20 inches by 25 inches or so. That's still not a great improvement for someone who isn't sitting near the front. Sure, if it's placed high enough, everyone will get a sense of the information, but will they gain deep understanding and truly be effectively engaged? Probably not.
If a TV Won't Cut It, What Is the Solution?
A digital projector. These devices allow you to feed a computer's signal in and project it onto any screen-like space in the classroom. If you have a real screen, great! Use it. Don't have one? Clear off a wall, tape newsprint to it, and -- presto! -- you have a screen now! And a decent digital projector can fill a screen as large as any wall in your classroom with a bright, clear image, making it possible for everyone to participate in a Web-based project or another utilization of digital resources. But there are a few things one needs to know about digital projectors.
How Bright Is Bright?
Lumens are. Every projector will promise to deliver a specific number of lumens, a measure of brightness. For regular classroom use, with the lights on, plan on looking at projectors with a lumens rating of at least 1,000, preferably higher. If you are offered a free one as a local business upgrades to a new projector, don't turn down the gift of an 800- or 900-lumen projector, but if you are shopping for a new one, the brighter the better. The difference can be remarkable! It has to be useable when the lights are on, though. Remember what happened in the classroom when you were a kid, and the teacher turned the lights off to show a film or a video? It turned into naptime for me more than once.
Most bulbs for digital projectors are $150-$300 -- not surprising, given the amount of light they need to produce to create the images they do. Therefore, it is important to pay attention to the anticipated bulb life. Look for a projector that offers 1,500 or 2,000 hours. At that rate, a projector used four hours per day, five days a week (an aggressive estimate, of course) will last 300-400 days -- up to more than two school years. And don't worry too much about the facts of daily in-school use, as most current projectors are portable and made for the road. As long as you take reasonable care of the projector, the bulb will provide good service.
LCD, or DPL?
LCD (liquid crystal display) projectors have three separate LCD panels -- one each for red, green, and blue components of colors -- that work together to create the image. DLP (digital light processing), a proprietary technology produced by Texas Instruments, has a single light-processing chip covered by thousands of tiny mirrors that move to control the light reflected out into the image. Because of their technical differences, DLP projectors, with their single light chip, can be smaller, while LCD projectors tend to create a slightly sharper image in side-by-side comparisons.
Because they are competing technologies, don't expect these differences to remain stagnant. When shopping for a projector for your classroom or school, be sure to look carefully at both kinds. A good question for your vendor might be, "I am a teacher, and so this projector needs to be rugged, portable, bright, and sharp. Would you recommend that I look more closely at DLP or LCD projectors, and why?" Listen to what they have to say, and then make your own decision. To read more about the differences, search the phrase "dlp versus lcd" online.
What About Resolution?
VGA? SVGA? XGA? Arrrgghhh! Acronyms can drive folks up the wall, but you really do need to pay attention to this. Resolution, in simplest terms, defines how clear the image your projector projects will be. The letters refer to different resolutions, or how many pixels (the small elements that comprise an image), your image will be made up of. The more pixels, the clearer the image. The common resolutions with a 4:3 ratio are SVGA (800 x 600 pixels) and XGA (1024 x 768 pixels).
Be aware that some applications, most notably Apple's iMovie, require XGA as a minimum video resolution. If you are going to use your projector to show movies your kids have created on iMovie, you'll need either XGA or an SVGA projector that can be pushed up to "pretend" it is XGA. Again, more questions for your vendor! Just remember: the higher the resolution, the better the image.
It's All About Being Connected
A projector by itself is really just an intensely bright flashlight. But even beyond the classroom computer, there are lots of things that can use the projector's power to make themselves large! Because of this, you want to pay attention to what kinds of devices can be connected to any projector you are considering.
Though the vast majority of current projectors connect to computers with the traditional monitor cable, some of the newest projectors may feature DVI (digital video interface) connectors, lots of flat blades instead of pins, requiring an adaptor to connect to a traditional VGA (video graphic array) monitor cable. Some projectors allow you to connect two computers at once, and toggle back and forth between them, while others provide wireless connections to your computer.
And don't forget good old RCA plugs, the red, white, and yellow ones we have all wrestled with behind the VCR. These will allow you to easily connect your VCR or DVD player to the projector, while a USB connector can allow you to connect a digital camera so that you can run a slide show of images through the projector directly off the camera.
This is the first of two blog posts on digital video projectors. Read the second post.