Assembling the Perfect DVD Presentation System: Getting Visual - Buyers Guide

Emedia Professional, Nov, 1999 by Mark Fritz

One advantage the rear-screen has over gas plasma is that rear-screen projectors (RSPs) are cheaper--but not by much. Prices for RSPs start at $6000, while a gas plasma monitor will cost you nearly $10,000. A second advantage is that they come in bigger screen sizes--while plasma tops out at 50 inches, rear-screen projectors are available in screen sizes up to 72 inches. Rear-screen projectors are available in higher resolutions (currently, gas plasmas top out at XGA). Many RSP cabinets have stereo speakers built-in.

On the other hand, rear-screen projectors are heavier than gas plasma displays, ranging from 70 to 300 pounds. And they are not as thin. While gas plasmas measure from 4 to 6 inches, most RSPs measure about 30 inches--just thin enough to get them through doorways. While bigger and heavier may be bad for mobile presenters, in some circles, their generous girth is considered a good thing. "This makes them harder to steal and borrow," says Bill Coggshall.

FRONT RUNNERS

Market analysts and salespeople usually put multimedia front projectors into one of five categories, based primarily on weight: ultra-ultraportable or featherweight (5 pounds or less), ultra-portable (under 10 pounds), portable (10-20 pounds), desktop (20-40 pounds), and fixed-installation or large venue (over 40 pounds, with weights in the hundreds of pounds not unusual). Projectors in the last category are intended for use in stadiums, auditoriums, conference facilities, trade show halls, etc. Once you get into this high-cost category, weight becomes the least of your worries.

Running parallel to projector weight is projector brightness, measured in ANSI lumens. Featherweight projectors typically put out between 300 and 600 ANSI lumens, while ultra-portables deliver between 400 and 1,000 lumens. Portables are capable of supplying 700 to 2,000 lumens and desktops 1,000 to 3,000. Large venue projectors put out from 2,500 to 12,000 ANSI lumens.

When is brightness important? Well, if you're presenting in high ambient light conditions--say, in some well-lit area where it is impossible or inconvenient to dim the lights--then you need more projector light in order to compensate. Also, the larger the image size you want, the more light you need. With a front projector, you make your image larger by increasing the distance (known as throw distance) from the projector to the screen. Therefore, the greater your throw distance, the more light you need.

Since image brightness is somewhat subjective, it's difficult to say how many ANSI lumens you need for a given screen size, but projector expert William Bohannon, chief scientist for Escondido, California-based Manx Research, recommends that people filling 100-inch screens use a projector capable of 2,000 ANSI lumens. Hundred-inch screens are frequently used in presentations because it is close to the maximum you can fit into a room with a standard eight-foot ceiling.

Underlying most multimedia projectors is one of three technologies: Cathode Ray Tube (CRT), Liquid Crystal Display (LCD), or Digital Light Processing (DLP).