|How To Pick A Video Screen For Digital Projectors|
|Home Theater Feature Articles Video Related Articles|
|Written by Jerry Del Colliano|
|Monday, 01 April 2002|
How To Pick A Video Screen For Digital Projectors
Some of the most exciting advances being made in the world of audio/video involve the new, smaller, lower-priced projectors, especially fixed-pixel digital devices such as DLP and D-ILA video projectors. For ultimate picture quality, the traditional CRT projectors, especially the most expensive nine-inch CRT projectors, are still the best in absolute terms. In more real-world applications, D-ILA and DLP projectors offer the ability to reproduce a far larger and far brighter picture by means of a less expensive, physically smaller projector that needs very little maintenance. With all of these advantages, there are still issues that you need to consider in order to get the biggest and best picture for your video setup.
A Dark Room = A Good Room For Video
I know this is an article about screens, but before you can talk about screens, you need to consider your room as it relates to the environment for a good video picture. The new digital projectors have their roots in conference system installations that need big-time brightness because of less than desirable ambient light situations. Unlike a CRT, the digital projector makes it possible to produce a passable video picture in a home theater that has some ambient light, but let me advise you now – the darker you can get your room, the better off you will be. Realistically, in non-purpose-built theaters, there is probably always going to be some light seepage during the day. You want to take steps to reduce this as best you can. Some remedies include thick, multi-layered, light-absorbing blackout drapes and light-blocking treatments for the outsides of your windows. In my system, I have my drapes all tricked out on a motorized Makita track, which adds to the "wow" factor, especially when you can dim your lights, drop your screen, close your drapes and open the drawer of your DVD player, all with the touch of one button. Your investment in making your room dark is a worthy one, no matter what your reasons for it.
Another requirement is to reduce the reflective surfaces in your room, including glossy paint, mirrors, anything shiny flashing around or near your screen, or even light-colored carpet. You have to consider your overall décor when weighing these factors, but they all add to the ambient and reflected light in your room. With the goal of "darker is better," you need to at least consider these issues if you are investing big bucks on any kind of video projector.
Contrast Is King
The biggest problem facing fixed-pixel digital projectors is contrast. As compared to CRT projectors, even the smaller, more affordable seven-inch projectors, the black levels are darker and the difference between black and white is more dramatic. On DLP and D-ILA projectors, blacks aren’t as crisp. In many situations, the problem can largely be addressed by a professional video technician. For the do-it-yourselfer, you can make significant improvements with accessories like the Avia Setup disc or the new Digital Video Essentials (coming out soon). In the case of D-ILA’s, some of the contrast issues are due to flaws in the factory gamma settings, because D-ILA is a technology designed for presentation and conference room systems first and home theaters second. Gurus like William Phelps, based in Silicon Valley, use special software to correct the gamma of a D-ILA to get reportedly dramatic improvements in contrast. DLP projectors from companies like Seleco have better than average contrast out of the box, because they are specifically designed for home theater applications. No matter which digital projector technology you decide on, according to Phelps, you are looking at 400:1 to 600:1 contrast ratios for contrast, depending on the quality of your specific chip. And yes, there are a wide variety of chips, which is one of the reasons why the Madrigal version of the D-ILA projector is $9,000 more than the JVC.
The hard fact is that, in order to get your digital projector looking as good as a CRT, you need to select the correct screen type. Video setup gurus, setup discs and the rest come next. Because of the brightness of these new projectors, the extra light output creates unique challenges to be dealt with at the screen level. Stewart, a leader in film screen manufacturing, has developed new screen technologies to specifically deal with the high light output of digital projectors. A GrayHawk screen has a relatively low 0.95 gain screen material and a gray background that absorbs extra light better than a traditional screen, which in many cases slightly amplifies the light output. The specific gray background color of the screen is chosen intentionally for the purpose of absorbing light. The newest Stewart screen for digital projectors is called a FireHawk and has a gray color, but also has a higher 1.3 gain as an alternative choice for digital projector applications.
According to Joe Kane (the author of the Video Essentials setup disc), as the result of his most recent tests on digital projectors, he has concluded that the optimum light output for a digital projector is 1.05 foot lamberts, which you can have your local dealer measure with a somewhat pricey light level meter. Lots of factors come into play on getting the light levels perfect in your room, including a combination of projector distance, screen size, ambient light and screen material. The advantage of working with a talented video setup guy and/or a dealer who really has some chops is that they will have the tools and the know-how to advise you on the best screen for your video system in your room based on measurements and math. In contrast, you local stereo salesman will try to sell you the screen he or she deems best based on what’s in stock and produces the best profit margin.
The reward for getting your light output correct, or at least really close to Kane’s goal, is dramatically better black levels. Critics of digital projectors knock the projectors for weak sauce black levels and, in many cases, they are right to do so. However, you will have built your system with the correct foundation to give you a head start towards success. Adding in great setup, gamma correction software and other video manipulations just gets you closer to the blacks you’d expect to see from a CRT without all of the hassle and expense of CRT technology.
Your wife keeps telling you that size doesn’t matter but, buddy, it does. So does shape and configuration – when it comes to your screen, that is. How far you sit from the screen is normally the determining factor for how big your screen should be. You are supposed to at a distance from your screen that is no greater than 1.5 times its diagonal width. In my system, I went for a larger distance than this standard, because I wanted a huge picture and knew I was ultimately going to get a D-ILA or DLP projector. My screen is a 100-inch 4:3 Stewart Studiotec 130 and I sit about 12 feet from it. I like the larger effect for the types of material I watch, including Philadelphia Flyers hockey games recorded on TiVo, Playstation 2, some movies on DVD and some HDTV sources when there is something on that’s worth watching. The risk is that, if you make the screen too big, you will need to move your head or eyes in uncomfortable or fatiguing ways when watching your system. You don’t want to go overboard with screen size, but if you have a very bright digital projector, I recommend that you use the horsepower you invested in to create a dramatic yet sensible picture. Be warned, even if you use a GrayHawk screen with a 0.95 gain, you may find that small screens result in too much light on the screen, which adversely effects your goal of 1.05 foot lamberts.
Screen shape is another issue you will need to address on personal terms, based on your current and projected usage. I predominantly watch hockey games, which are shown in the traditional 4:3 aspect ratio, as is Playstation 2 material and most of what I watch on TV. The large majority of the DVDs I watch are in 16x9 aspect ratio, which still creates a pretty big picture on a 100-inch screen. The same goes for HDTV programming. The very top and bottom of the screen are blank, but the image is still reasonably large. I had a discussion with an industry friend of mine, who primarily watches movies and HDTV on his big home theater screen. In his case, a 16x9 screen makes the most sense. 4:3 sources, like most broadcast TV, will look small on the 16x9 screen. In other words, you want to get the optimal screen for the sources you watch most.
My father got burned with this aspect ratio situation when he invested in a theater system with a first-generation 42-inch plasma monitor. Not only did the plasma monitor not have the brightness or black levels to keep up in a very bright room for daytime viewing, 4:3 sources looked pathetically small with a 26.1 inch diagonal picture. You can stretch the image, but the results look awkward at best. I am not sure that there is an absolute right or wrong on the topic of screen shape at this time. If HDTV were a more dominant broadcast format, you could make an argument for definitely investing in a 16x9 screen. However, for now, you need to consider your specific viewing habits, then how you think they will change over the next few years, before you make your screen decision.
I hope this article gives you some good ideas about how to go about setting up a state-of-the-art video system that is built from the ground up to look and perform to standards that will have you drooling in amazement for years to come. When it comes time to make the move to a big, badass system, be sure to interview your better local dealers for their opinions on video setup. Find out who has trained them and how many systems they have designed. Ask them if they work with or subcontract high-end video projector setups to experts like William Phelps, Nick Griecko or others. If they do, you know you are dealing with top-notch installers who know what they can do well on their own and when to call in the pros. Trust me, when all is said and done, you will appreciate the difference, and the leg work you have done in advance of your purchase will seem well worth the effort.
Click here to read Jerry's review of the Madrigal Imaging MPD-1 D-ILA Video Projector.