Cheat Sheet: Planning for 3D
Surprisingly little has been written about calibrating displays to show 3D content, or setting up a display and its environs for optimal viewing. Still, here are a few tips for doing a pro 3D install.
BEFORE YOU BEGIN
Surprisingly little has been written about calibrating displays to show 3D content, in part because much of what we know about calibrating 2D displays applies to the 3D experience. After all, a 3D display or projection screen is still a 2D surfaceand in most cases, the 3D display will also be used to show 2D content. Therefore performing all your normal 2D calibration, such as setting brightness and contrast with a PLUGE (Picture Line-Up Generation Equipment) pattern, adjusting gamma for movies, and matching color spaces to the content, is especially important because mistakes in 2D setups will be exaggerated in 3D.
CALIBRATION FOR 3D VIEWING
Because of the nature of 3D projection technology, everything from glasses to lens shutters limit the amount of light that reaches the eye and creates possible color shifts, so calibration is important. Most 3D projection systems will also need to display 2D content, so ideally, the technology you choose should retain dual calibration presets for color temperature, lumen output, and basic settings. Next, focus on:
Credit: Kevin Mazur
For a big screen, you may want a dual-lamp projector. In 2D mode, a single lamp at 80-percent power can produce 25 foot-lamberts (fL), which is ideal. By some estimates, 3D viewing systems reduce light throughout by 80 percent. So in 3D mode, you’d need both lamps working at 100 percent to produce 60 fL, which would then be reduced to 12 fLmore than adequate for viewing 3D in a dark environment. (The Society of Motion Picture and Television Engineers specifies 4.5 fL for commercial 3D theaters, though many pros say it’s too dim.)
Color shifts. As with 2D displays, use your PLUGE pattern to set contrast and brightness, but with the projector in 3D mode and wearing 3D glasses. Store those values in a different user setting. Next, display a full white field to the projector, with the projector in the 3D mode. You’ll need a spot meter, rather than an incident meter, to accurately determine color performance. The spot meter, shooting through the 3D glasses (which must be in the “on” mode) will capture the color shift produced by the glasses, screen, and the environment. With those measurements in hand, the final step is to adjust the color point as close as possible to x=0.312 and y=0.329 without dramatically affecting light output.
SETTING UP THE ROOM
At September’s CEDIA Expo in Atlanta, experts from THX offered tips for installing 3D displays, whether in a home or another controlled viewing environment. (THX has also begun to include 3D instruction in its professional workshops. Visit thx.com/professional for more information.) Among THX’s guidelines:
1. Ensure a big enough screen. Whether projection or flat-panel display, bigger is better when it comes to 3D, though THX doesn’t talk in terms of simple diagonal screen measurements. In general, because of the way our eyes focus on 3D images, it’s best to use a bigger screen positioned farther from the viewer. THX says a TV or projection screen “should create a field of view no larger than 50 degrees and no smaller than 36 degrees.”
2. Pay attention to seating angles. While some 3D technologies offer better off-axis viewing than others, THX believes that to create the best possible 3D effect, your seating area should be within a 30-degree zone, with a maximum viewing angle of 45 degrees. Outside that viewing zone, certain 3D effects will look unnatural.
3. Avoid visual distractions. One reason some 3D demonstrations at tradeshows such as InfoComm or CEDIA Expo come off poorly is that there is too much going on around the display—other screens, explanatory signs, booth decorations, etc. All these visual clues anchor the view in reality and blunt the 3D effect, which, after all, is about tricking the brain to see something that’s not there.THX recommends a “clean, 120-degree open space between the main seating area and the screen.” No furniture, lighting, glossy bezels, or drapes. If you can clear out a 160-degree space, it’s even better. THX says you should also avoid ambient light reflecting on the screen. Anything within a user’s field of view that’s not the 3D display only lessens the 3D effect.
Some display technologies are less forgiving of off-axis viewing than others. Considering 3D is best experienced within specific viewing angles, take extra care to plan your 3D installation when using either of these product types:
LCD flat panels. Not all LCD TVs offer wide viewing angles to begin with. So if LCD is your 3D technology of choice, make sure you get the best screens you can and/or plan to limit the viewing zone.
Silver screens. Experts say that silver projection screens, which can be used effectively for passive 3D viewing, don’t look as good when viewed from too far to one side, so don’t sit viewers too far from the center line.