Display & Presentation

Eeny, Meeny, Miny, Mo...

• By Malcolm Montgomery
• 02/01/08

The market abounds with new projectors designed for generalpurpose classrooms and small- to mid-size lecture venues. But choosing the right one remains a challenge.

AS TECHNOLOGY AND TEACHING requirements continue to evolve, you'd think the choice of which data projector to buy would be easier because there now are more products with more capabilities. Yet just the opposite is true: The sheer number of projectors and myriad combinations of available features can be overwhelming, making it really tough to identify the right solution for your institution. Add to that the fact that today's purchase may have to last five years into the future while technology evolves around it, and it's a wonder that technology managers don't just give up and throw darts at a list on the wall.

How, then, to choose? As of my last reckoning, there are over 3,000 makes and models of projectors on the market, and probably as many variations in the situations in which they will be used. Without knowing your specific circumstances, it would be hard for any consultant to tell you what he thinks would be your absolute best choice. Still, there are guidelines that can make a world of difference as you navigate the market. Let's begin by reviewing a few good rules of thumb for selecting a projector; then we'll look at some of the new features now available that help solve some of the long-standing problems we all encounter with projection. The emphasis will be on general-purpose classrooms or venues with seating from 25 to 50 students.

Get the Basics Right

Though it may seem obvious at first, in order to make sure that nothing is overlooked, ask yourself: What do you want the projector to do? It's also a good idea to prioritize the performance objectives according to the particular needs and the resources available at your institution. Special applications may affect the details and priorities, but for general classroom use the following requisites usually top the list:

• Bright, clear image, with easy-to-read text
• Aspect ratio: standard 4:3 or widescreen 16:9
• Reliability; instructors need to count on the equipment. (How often might a projector be out of service for repairs?)
• Manageable TCO (total cost of ownership) including purchase, installation, maintenance, and consumables (especially lamps). Don't neglect to check the warranty.
• Control and monitoring via IP or RS-232

Let There (Not) Be Light

The fundamental requirement of any projector is that it displays an image that is clear and bright. A good rule of thumb is to choose XGA (1024x768) native resolution, and an image (screen) size that has a height of one-fifth the distance to the farthest seat. This ensures that the detail in images and small text can be clearly seen. For widescreen, there are two main choices: WXGA (1280x800) native resolution, to display high-definition 720p images (one option: the Sharp PGF320W, priced at $2,995), or for greatest detail (1080p), go for a projector with 1920x1080 native resolution (such as the Mitsubishi FL7000U, a bit pricier at $14,995 list).

Next to size, the most critical factor in legibility is contrast-contrast ratio between the darkest and lightest parts of an image as it appears on the screen. How dark the darkest part can be depends on two things: a) the projector's inherent light leakage in the dark parts of the image, and b) the ambient light falling on the screen surface. How light the brightest part can be depends upon how many lumens the projector produces, divided by the area of the image in square feet. For general classrooms, the ratio should be no less than 10:1.

Yet, what does this mean in practice? To achieve acceptable contrast, you'll need to determine the screen size (as above) and measure the ambient light level falling vertically on the screen surface under teaching conditions. (If you do not have access to a light meter, or are planning a yet-to-beconstructed facility, you might use five to 10 footcandles as a stand-in, assuming pretty good light control. If you can turn off the room lights at the screen, dim the lights over the students, and block out window light, this should be close.)

Use the following formula: Lumens required = 10 x image height x image width x ambient light (where image height and width are in feet and ambient light is in footcandles, measured with a light meter placed vertically against the screen or estimated as mentioned above).

For example: In a room where the farthest seat is 30 feet from the screen, the image height should be one-fifth of that distance, or 6 feet. For a standard 4:3 aspect ratio, the width would then be 8 feet. Assuming good light control (7.5 footcandles): Lumens required = 10 x 6 feet x 8 feet x 7.5 footcandles = 3600

But what about the projector's inherent light leakage? It is listed in the projector specs as the contrast ratio. If the contrast ratio of a projector is 400:1, that means for every 400 lumens the projector produces, it leaks one lumen. In the example above, the leakage would come out to 9 lumens, which spread over the six-by-eight-foot screen, would amount to less than 0.2 footcandles, or just onefortieth as much as the ambient light. This additional light is too little to make a meaningful difference in the legibility of the image, and with higher ratios, even less so. In a darker room, the projector's contrast ratio makes more of a difference, but even then it tends to be more subjectively attractive than being objectively more legible.

The formula gives you the minimum number of lumens the projector must provide. If you can afford more, so much the better, especially since projection lamps lose light as they age and may only be half as bright before they reach the point of failure. Most importantly, anything which adds to the ambient light level at the screen increases the number of lumens required. That light can come from unshielded light fixtures, inadequate window treatments, view panels next to doors, safety lights that cannot be turned off, and so forth. Do everything in your power to minimize illumination from these sources.

By the way: These rules are far from arbitrary, as they are based on psychophysics and human perception as applied to viewing typical images used in higher education. For this reason, they scale to nearly every venue, from seminar rooms to large auditoria.

Heat Kills

If your institution is like most, you are under tremendous pressure to keep every classroom operating. The heavy use of A/V takes its toll on projectors in particular, because the heat and high voltage associated with the lamp stress all the other components as well. To avoid premature equipment failure (not to mention shortened lamp life), choose a model that is made for installation. Don't succumb to the temptation to install an inexpensive ultralight portable projector as fixed equipment; these models usually sacrifice robust design to achieve their small size.

Having said that, a lighter engine design has been incorporated into several new models suitable for installation. The new design incorporates a power supply that feeds AC, rather than the usual DC, to a newly designed lamp. The net result is a predicted 50 percent extension of lamp life from a typical range of 1,000 to 1,500 hours, up to 2,000 to 3,000 hours.

It's a good idea to select a projector that has a low power mode in which it can still produce the required number of lumens, as we calculated previously. (Products such as the Dukane 8755G-RJ and the Optoma TX761 have this feature.) Not only will the projector run cooler and last longer, but the lamp life will increase by around 50 percent, and the lower fan speed will result in a 3- to 6-dB drop in noise-an audible, if not dramatic, reduction. And again: Projector lamps dim as they age. A new lamp that is bright enough in low-power mode but eventually dims below an acceptable level may have its useful life extended by then shifting to high-power mode.

Since the major cause of equipment failures during use is lamp failure, projectors with two lamps instead of one, such as the Barco iCon H250, go far to prevent disruption of teaching. If you select a model with sufficient lumens in single lamp mode, it will cost no more than a regular projector to operate. In fact, it may cost less if (in an attempt to head off failure in use and the consequent disruption) you are into the practice of replacing lamps after a fixed number of hours. Dual lamp projectors allow you to choose the use of two lamps, one lamp only (with the other as backup), or else alternate one lamp with the other on subsequent uses. Running only one lamp has the advantage that the backup lamp is always new. When the first lamp eventually fails, it can be replaced and become the new backup.

Dual lamp projectors have another use in venues where the light level varies over the time period they are in use. For example, rooms suffering from high levels of ambient light during the day (say, because of insufficient window coverings) will need a brighter projector for use during those hours. It is possible to use a smart control system or remote projector-control software to turn on both lamps during the day for a brighter image, but only one at night when the room is darker. The reduction in hours the projector is operated at high power improves reliability and reduces operating and energy costs.

Preventive Maintenance

Many smaller DLP projectors, such as the IN37EP and IN35WEP from InFocus, now have sealed optical blocks and are designed not to need air filters that have to be cleaned or changed. This is a great advantage because filter cleaning is a timeconsuming and inconvenient procedure requiring a ladder and enough time to set it up, clean the filter, and put it away.

Most LCD projectors, however, do have air filters that need maintenance, and keeping the filter clean is critical to the reliability and lifespan of both the lamp and projector. To make the task as quick and easy as possible, the filter holder should be readily accessible for replacement or quick cleaning with a handheld vacuum cleaner. Filter cleaning is never convenient, however, as the vacuum cleaner requires a power cord to be plugged in, and the equipment must be used atop a step ladder. This, in turn, may require a second person to assist for safety. What's more, filter cleaning can't be done between classes, and with the busy schedules at many schools, evenings and weekends are often the only options left.

Fortunately, a couple of projectors have recently come on the market boasting an innovative filter system that requires almost no cleaning or replacement. Panasonic's PT-100 series uses an auto-rolling filter (ARF) that periodically advances new filter material automatically. Eiki also uses a self-advancing cartridge air filter in its LC-X80 and LC-XIP2000 models. Replacement filter cartridges cost more than ordinary filters ($75 for the Eiki), but they should easily pay for themselves in reduced labor costs. Consider these especially for large lecture halls and auditoria, where there are high ceilings that require tall, unwieldy ladders or even scaffolding. Just as much to the point, these devices do not depend on staff finding the time to keep to the maintenance schedule. The adage, "When you are up to your neck in alligators, it's difficult to remember your objective is to drain the swamp," applies here. Preventive maintenance always yields to immediate needs, and is frequently deferred (sometimes forever). Which brings us to…

Time Out for Repairs

Even with the best preventive maintenance program, equipment sometimes fails. In the simplest case, it's the projection lamp. Most classroom projectors have lamp assemblies that the user can replace-a few even without unmounting the projector. Worst-case scenario: The support technician can change out a bad lamp in the few minutes between classes and get the projector right back into service. I suggest buying one spare lamp assembly for each model of projector in use, or more if you have difficulty replenishing your stock quickly, own more than 10 of the same model, or experience very heavy usage. But lamp assemblies are expensive ($300 to $500), so don't overdo it, especially since the warranties usually start upon delivery and last only 90 days. (You don't want the warranty to run out while your lamps sit on the shelf. Nor do you want to be holding spare lamps when the projector approaches the end of its useful life.) Two NEC models (VT700 and VT695) have an advantage here in that the lamp is warranted for a full year, or 500 hours, whichever comes first.

After replacing the lamp, if the projector still doesn't work, you will need to send it out for service. This is where the response time and service level of the manufacturer (and/or your local vendor) become critical. Some warranties, like that of the NEC VT700 and VT695, give you the choice of having your unit repaired and returned within three business days, or having an exchange unit shipped out for delivery the next day. In the latter case, if you notify the service center of the failure on a Monday, for instance, you'll receive your replacement on Tuesday. That's hard to beat!

Still, read warranty options carefully. Almost all cover lamps for only 90 days, and projector parts and labor for anywhere from one to five years. The main variations: whether they will cross-ship a replacement unit before you send yours out, and who pays the shipping costs. Eiki is the only manufacturer I know of that limits not only the length of ownership, but the number of hours of projector use as well. This is not unlike automobile warranties, which typically cover some number of miles or some period of time, whichever comes first. The number of hours warranted by the company is 6,000 hours for the projector, 500 hours for the lamp, and that equates to about 40 hours per week. This would have the effect of shortening the warranty for heavy users who run the projectors five or six days and evenings a week. Also, make sure that you consider that the lamp warranty is limited not only to 90 days, but also to 500 hours-whichever comes first. And if the lamp fails during the warranty period, you don't get full reimbursement; it's prorated based on the number of hours that it worked before it failed. Caveat about projectors in general: Read the fine print. That brings us to the following question:

Are Some Brands Good and Others Bad?

Everyone wants to know which brands are good and which are bad. Unfortunately, there is no comprehensive independent organization that conducts statistically sound tests and surveys for data projectors as, say, Consumer Reports does for home appliances. Instead, we all have to look to our own experiences with the equipment, and those of others. My own take is that there is no consistent difference in reliability across the various manufacturers. In fact, just a few manufacturers actually make the projectors that many other companies brand, market, and sell under their own names. (For that matter, some manufacturers actually outsource the fabrication to an even smaller number of factories in China.)

That is not to say there are no differences between specific models or makers. On occasion, I have seen an otherwise reliable brand create a new model with a high failure rate of a particular component such as a power supply. Often, the manufacturer recognizes the problem, and may even initiate a recall campaign and provide free loaners. And sometimes, what seems like a design problem may actually be due to something else. In one instance, a new projector model seemed to burn up lamps in only two hundred hours or so. It turned out that the problem was actually a bad batch of lamps. I rarely would regard one problem model as a reason to reject the entire line.

Which factors, then, should you consider when choosing a brand? First, of course, you need to work from a list of the features that are important to you. We have already mentioned a few: a bright, clear image; longer-life AC lamps; high/low power modes; self-cleaning (or no) filters; dual lamps; user-replaceable lamps; service level and warranty. But you need also to keep up with projector technology, to truly assess the best products for your own campus needs.

Projector Technology

There are presently three basic chip technologies that projectors used to create an image: LCD, DLP, and LCOS. In LCD projectors, a light from a metal halide lamp passes through a prism that separates the light into red, green, and blue streams, which pass through separate poly-silicone panels that act as gates. Individual gates, which are quite tiny, can be opened according to the brightness of that color component for each pixel. By combining the three colors in varying degrees, a wide range of colors and shades is created.

In DLP projectors, the image is created with tiny mirrors instead of gates. Each mirror reflects light out either to the lens or into a light-absorbing heat sink. By flipping the mirrors very rapidly between these two positions, the strength of the light can be varied. In addition, there are both three-chip and single-chip DLP projectors. Three-chip models use a prism like that of LCD projectors to create color, whereas single-chip DLP projectors pass the light through a spinning color wheel containing the primary colors. The single chip does the job of three by reflecting the appropriate amount of light for, say, the red component of the image, only when the red filter passes before it. Likewise, it reflects only the green portion of the image when the green filter comes around. This process occurs quickly enough that persistence of vision causes the primary colors to blend together and appear as the appropriate color. However, the image from a three-chip DLP projector is considerably better than that of a single chip, which has a visual artifact called the "rainbow effect." It's perceived as brief flashes of red, green, and blue shadows surrounding very bright objects on a dark background. It can cause eyestrain as well as distraction.

LCOS chips use reflective technology similar to DLP's moving micro-mirrors, but are also akin to LCDs in that they use liquid crystals that are fixed in place. They are capable of creating excellent images (and with no "screen-door" effect), but they cost more. Look for the price to drop in the coming year as improvements in the manufacturing process lead to expanded use in consumer viewing products. If you're interested in LCOS projection technology, consider the Canon REALiS series, which uses LCOS chips to create top-notch images at a substantial 4000 lumens with a contrast ratio of 1000:1. And take note: The widescreen version, SX7, is the first moderately priced projector I have seen that is capable of being calibrated to the demanding color reproduction requirements of Adobe RGB and sRGB color spaces. Then again, your color reproduction requirements may not be as stringent, especially if you're in the market for multiple projectors and you have very real budgetary issues. See "Projector Chip Technology: What's the Difference?", to help you determine the impact of the various technologies.

In the be-all and end-all, when it comes to projectors, a little solid knowledge goes a long way before you plunk down your institution's IT dollars. Take heart: By using this article and the projector model specification comparisons in the chart below, you'll find yourself way ahead of the Eeny Meeny Miny Mo game.

Malcolm Montgomery is president of EduTech Consulting Services.