Professional monitoring for live 3-D production takes passive approach

While consumers struggle with the passive (more affordable) versus active (expensive, better resolution) glasses debate for 3-D viewing, production companies appear to have made their preference known for the less costly passive system when monitoring camera sources and program feeds during a 3-D production. It’s critical that stereographers see and adjust images correctly before consumers see them to ensure a comfortable viewing experience.

Meeting this demand for practicality, JVC, Marshall Electronics, Panasonic and Sony are marketing a new generation of professional reference monitors that leverage the Xpol circular polarizing filter so 3-D content can be viewed with circular polarizing (passive) glasses.

“When you are in a truck, you don't want to use expensive shutter-style glasses because they get misplaced and stepped on,” said Jason Goodman, a stereographer with 21st Century 3D (New York and Los Angeles). “Polarized glasses and passive monitors might not give the best resolution, but the system is practical and gives us enough of a natural color rendition to create a beautiful 3-D image that is engaging for the audience.”

With the Xpol system, a trademark of Arisawa Manufacturing in Japan, the dual signals coming from the 3-D stereoscopic camera rigs are interleaved within the monitor, so the left- and right-eye image data is displayed as alternate scan lines or alternate rows of pixels. The left and right eye each gets different images, which are combined on the screen as they are presented to the viewer. It gives the stereoscopic crew a good horizontal viewing angle, but the vertical viewing angle is somewhat limited.

With an active-shutter monitor, the left-eye and right-eye information switches back and forth between lenses on the glasses, providing, some say, a higher-quality 3-D image; however, the cost of the glasses, which require batteries, at $75 to $150 per pair is prohibitive.

“Nobody is advocating the shutter-type glasses because of cost, and when the glasses have shutters in them, there’s all kinds of problems with viewing angles when looking at multiple monitors inside a production truck,” said Dave Walton, vice president of marketing for JVC Professional. “The current trend is to use a passive system that uses inexpensive polarized lenses and a polarizing filter across the front of the LCD flat panel.”

JVC introduced a 46in professional reference monitor at NAB this year that features the company’s "3-D visual engine." It’s compatible with both line-by-line and side-by-side camera rig signal inputs. At IBC in Amsterdam next month, JVC will show a 24in production monitor that features built-in alignment tools to help stereographers and cinematographers adjust cameras on the set.

Marshall Electronics also makes a 24in 1920 x 1200 LCD panel that displays 3-D images via a circularly polarized glasses system. There are four inputs for the simultaneous monitoring of two (right eye/left eye) HD-SDI signals, 2-D images side by side and butterfly display options for looking at left-eye and right-eye data separately. It uses a horizontal alternating polarization method to show converged 3-D images.

The monitor employs a 3-D optical filter applied to the surface of the flat-panel display. By using circularly polarized glasses, the user can simultaneously view multiple 3-D monitors in a production or multimedia environment. This monitor also supports in-monitor display functions through RS-422/RS-485 connections (in quad-view mode).

Earlier this year, Panasonic introduced a 25.5in 3-D LCD production monitor with 1920 x 1200 resolution. The BT-3DL2550 provides 3-D display with true-to-life color in a durable, production-tough LCD panel package. Joe Facchini, vice president of sales and product management, said that the monitor features dual HD-SDI inputs for simultaneous display of left-image, right-image and combined 3-D signals. Green and red tally lamps on the front panel, an embedded audio decoder (through the headphone jack), time code display, closed-captioning (through video input only) and an audio level meter that can display of up to eight channels are also included.

With an in-plane switching panel and 10-bit processing circuit, the monitor offers six color settings (SMPTE, EBU, ITU-R BT.709, Adobe 2.2, Adobe 1.8 and D-Cinema) and a 3D look-up table for calibration. It also supports 1080i, 1080p and 720p playback and offers pixel-to-pixel function in 720p mode.

Sony offers both a 42in and 24in 3-D monitor, each with a micro-polarizer 3-D filter across the front panel. The complementary glasses use a circularly polarized filter that displays the right signal on the odd scan lines (clockwise) and the left signal on even lines (counter clockwise). The 24in version’s aspect ratio is a bit wider than 16:9. It provides 1920 x 1200 resolution for dual HD-SDI streams (with an optional BKM input adapter) and a wide viewing angle. The 42in model features full 1920 x 1080 HD resolution for each channel.

Images are displayed in a field-sequential HD-SDI scheme (1080/30PsF, 25PsF or 24PsF) or DVI (line-by-line 1920 x 1080/60p, 50p). Both models, part of Sony’s Luma line, will be shown at the IBC show in Amsterdam in September.

“We make both types of 3-D systems (passive and active) but understand the clear need among production crews for affordable solutions, and that means a passive system,” said Alec Shapiro, senior vice president of Sony’s Broadcast and Production Systems Division. “The circuitry is improving at such a rapid pace that the resolutions we're getting with these new monitors is better than any CRT product we've ever produced.”

Of course, there are a lot of other tools stereographers need besides a monitor. While the monitors combine the signals onto a single screen, the 3-D crew also needs to look at the two images coming from the cameras separately for fine-tuning. For this they use a stereoscopic processor that allows them to look at the combined 3-D image with glasses on as well as see each individual image to adjust convergence. They might also use a waveform of the left and right images, so they can match the levels from a pair of HD cameras.