Projectors Get Brighter, More Powerful, and More Versatile

Let's take a closer look at how much an installation projector haschanged in design:

Video and computer sources: In the good old days, a typicalinstallation CRT projector might have to handle interlaced video andthe occasional VGA signal. In most cases, video arrived in a compositeformat (sometimes component RGBS, but not too often). That wasn't toostrenuous a workout.

In contrast, our 21st-century projector has a plate that's slightlyoverflowing. In addition to composite video, today's installation LCDprojector will support Y/C (S-video) and YCbCr component interlacedvideo formats. For progressive-scan computer displays, it will acceptVGA 640x480 (almost extinct now), SVGA 800x600, XGA 1024x768, and SXGA1280x1024 pixel sources.

Sharp's XG-P20XU

Just for the heck of it, throw in support for the ATSC DTV YPbPrformats (480i, 480p, 720p, and 1080i). Oh--and don't forget variableaspect?ratio sizing, such as the ability to toggle between 4:3 and16:9, or display anamorphic video in the correct aspect ratio. Did wemention DVI support? Yes, many installation projectors now have directdigital inputs.

Brightness and Contrast: It used to be a big deal when youcould squeeze over 200 ANSI lumens from a CRT projector. Even the bestdesigns nowadays can't do much better than 350 lumens of brightness.The reason? Resolution and brightness are forever intertwined in aCRT--drive the tube harder to get more light output, and the spot sizeof the electron beam grows in size, reducing the effective resolutionas the beam traces images onto a screen.

LCD projectors have no such limitation--they're basically lightshutters, like Venetian blinds. Their ability to resolve detail in animage is limited only by their native pixel count, regardless ofwhether the projector is turned on or off. Cranking up the brightnesshas no effect on the resolution of the projected image (although itdoes add heat to the optical system).

Enhancements in the efficiency of projection lamps, lightcollimators and condensers, optical prisms, and dichroic filtermaterials have boosted the light output of LCD projectors to almostunbelievable levels. Early LCD installation projectors werehard-pressed to deliver 300 to 400 lumens in 1996. Five years later,it's no big deal to extract over 2000 lumens from an installationprojector.

That level of performance was once the exclusive province oflight-valve projectors, 200+ pound behemoths that required a 220-voltsource and a full-time crew to set up and maintain. Even the simplestdesktop and portable LCD projectors are capable of 1000 to 2000 lumens,and LCDs equipped with micro lens array (MLA) technology will boostthat number by 50%.

What this really means is that installation projectors can work in awider variety of lighting environments, from classrooms equipped withbright fluorescent lamps to trade show booths, business theater, andchurch sanctuaries with high daylight levels. You'll still want to keepas much ambient light from spilling onto the screen. But having theextra horsepower gives you more projection options.

Contrast was another issue with CRT projectors. While CRTs werecapable of excellent grayscale reproduction and good black levels--andstill are--they were hamstrung by low light output. In contrast, awell-designed LCD projector can attain contrast ratios routinelyexceeding 200:1, and in some cases will do better than 300:1. That'smore than enough for display of video and computer graphics invirtually any room, under any lighting.

Screen Sizes and Projection Throws: Remember those oldcurved, high?gain front projection screens that used to be standardequipment with CRT and LCD projectors? They're history! Nowadays, theway to go is to use a flat, low-gain matte finish screen to create thewidest viewing angles possible. All of the imaging horsepower isprovided by the projector.

Having extra lumens in your pocket makes it possible to use evenlarger screens. This is a tremendous benefit to those in the rental andstaging business, who are often working with 15' and wider front andrear screens. Venues that depend on Image Magnification (IMAG) rely onlarge screens, as their audiences can be seated 100' or more from thescreen.

Thanks to the inverse square law, doubling the projection throwdistance to a given screen to double the image size requires four timesthe original image brightness. That level of illumination wasn'tfeasible with CRTs, but LCD technology is another story! If you can'tget enough horsepower from a single installation box, simply stackanother one (or two, or three) on top of it. Converging the images is afairly simple task, thanks to the single-lens design.

Projection lens options have increased with higher brightnessprojectors. It's possible to have extremely short throw lenses (.9:1ratio) and extremely long lenses (over 5:1 ratio) and use the sameinstallation projector with all of them. While the f-number ratio mayrange from as low as 1.7 to as high as 3.4--a range of over twof-stops--there's sufficient illumination in a 3,000 to 4,000 lumensprojector to maintain a bright, contrasty image at all focallengths.