A Time For Reflection, or “how to choose the proper fabric for your front projection screen.”
One of the tasks of a “home theater expert” is to help a client decide on the correct screen fabric for the theater. On the surface (pun intended) that may seem like an unimportant task. However, the right screen surface can make the difference between a poor picture, a decent picture, and a great picture. There are several great websites with a great deal more information on choosing the right screen surface than I am planning to cover here but this blog will cover a few of the basics.
Basically, here are a few of the questions I would ask a client to help pick the right fabric.
1) Will the speakers be installed behind the screen?
2) Do you have the ability to completely control the amount of light in the room?
3) Will you watch the largest percentage of what you watch with the lights off, or nearly off?
4) What are the dimensions of the room, and what will the seating layout be?
As you can imagine, there are several screen companies out there to choose from. Some names are more recognizable than others, but they all make different screen models that are better suited for certain applications.
The first question above determines if we will use a perforated screen or not. That’s the way a movie theater works in that the front speakers are installed behind the screen. The perforations are so that the sound is not muffled. Those screens also typically have a lower screen gain (more on that below) than a matte white or white screen.
When choosing screen fabric, you will most often select a screen that is white or gray (some are even black!) That choice is usually determined by your ability to control ambient light conditions. While most people will use a different light level while watching different material (I usually have low level lighting while watching sports, and completely dark for movies), you’ll want to let your home theater expert know what the lighting conditions will be most of the time. When the vast majority of your viewing will be done in very low lighting (and you can control the amount of light in the room) then a white screen is usually the better choice. There are still factors that may necessitate the choice of a gray screen (like an extremely bright projector) but generally speaking, a white screen is the better choice if light can be completely controlled and you plan to watch mostly in the dark. Conversely, a white screen is not the best choice if the room is multi-purpose and there are windows that cannot be completely darkened or you plan to have the lights on a lot. Since the job of a front projection screen is to reflect the light that comes at it, a white screen would wash out the image in these conditions.
Stewart Filmscreens introduced the industry’s first gray-based reference standard screen in 2001 with the GrayHawk screen when projector technology was moving from CRT projectors to brighter projector types like DLP, LCD and LCoS. Early models of these projectors were very bright, but had very low contrast ratios and did a very poor job on black levels. Gray screens were designed to help those projectors produce better black levels. Today, many projectors have contrast ratios of 70,000:1 so using a gray screen isn’t necessary in rooms where light is controlled.
The next element in screen choice is screen gain. Gain is a measurement of the reflectivity of any screen or projection surface. The gain number represents a ratio of the light that is reflected from the screen as compared to the light reflected from a standard white (magnesium oxide) board. Therefore, a screen with a gain of 1.0 will reflect the same amount of light as that from a white board. A screen rated at 1.5 gain will reflect 50% more light as that from a white board, whereas a gray screen with an 0.8 rating will reflect 80% of the light from a white board. Gray screens and high contrast screens often have gain levels of .8 and so less light is reflected off the screen than it receives. White screen gains are usually 1.0 to 1.5. So, once the home theater designer and client have decided on a projector and have determined lighting conditions, the choice of screen gets much easier.
The target for screen choice and projector choice is to recreate the experience at the movie theater. Ideally, the projector and screen should produce a minimum least 12 foot-Lamberts when measured and the ideal is 16 foot-Lamberts (SMPTE and THX standards.) So choosing a gray screen with a .8 gain and a projector that only has 700 lumens is probably going to produce a dim picture, especially if the projector is mounted at its farthest throw distance and the screen is large.
Screen companies are very good to help out when determining which screen to go with. As you can see, even from this brief overview, a lot goes in to getting that picture to look just right. Too much gain with too many lumens can produce hot spots, unbalanced color and eye fatigue while too little gain, low lumens, and ambient light can leave a picture dim, or washed out. Be sure when you’re ready to purchase, you go over the details with your home theater expert. You’ll be glad you did!
-Clay Hankins is the CEO of The Audio Guy, LLC located in the
Dallas, TX area and serving the Dallas Home Theater, Media Rooms and surrounding
DFW area markets.
Posted
10-08-2009 9:40 PM
by
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