THX Certified Display-bw 425

(May 4, 2010) Director George Lucus created the THX Certification program in 1983 to institute audio and film reproduction standards for movie theaters. Later, THX began an audio certification program for home theater. More recently, THX introduced new standards for home HDTV certification (for more on THX history click this link). To receive THX certification a display must pass a battery of tests incorporating over 400 data points.

THX chose the HD Guru as the first journalist to reveal details about its display testing program. (Disclosure: THX paid expenses to visit its San Rafael headquarters)

Our host provided a complete copy of its requirements and specifications for certification with the understanding (for competitive and business reasons) we would only publish the list of test categories with a limited number of the exact specifications. We jumped on the chance to pierce the armor of secrecy surrounding THX’s video standards.

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Inside THX’s test lab, we observed their array of test signals and procedures. In addition to the legacy test signals we and other reviewers use to evaluate HDTVs, THX created some of their own patterns (see photos).

THX tests signal processing, deinterlacing, color points, black levels and white levels among others criteria. They perform additional testing of display properties that are generally too time consuming or require special test equipment the HD Guru and our fellow reviewers don’t possess. Here is a link to a never before released list of THX tests.

THX Test Equip. 425THX Testing Lab 1 425

The Secret Sauce

Below, the techies among our readers can see the seven of the dozens of specifications a display must meet for THX Certification. These tolerances are quite tight.

A brief explanation of the seven items

1) Primary and secondary color points must be within a±0.005 variation.  2) Low panel reflectance allows viewing in an environment with lamps. Please note no anti reflective filter is 100% effective.  3) Uniformity assures no dark or light areas on the panel, a problem that plagues many LCD (and LED-LCD) panels. 4) Off axis color accuracy assures minimal color shift as one moves up to 45º off center, another common issue with many LCD panels. 5) Tests for residual images (called image retention) on a plasma display. 6) Confirms display of 100% of the image, assuring no aliasing artifacts with 1080i/1080p content. 7) Assures the signal processing within the display provides full resolution without adding undesirable artifacts.

THX provided the following italicized section:

The items below are a snapshot of some of requirements to achieve THX Display Certification. The test sample provided by the manufacturer must meet or exceed all THX requirements, as listed in the THX specification, when measured in our San Rafael facility. All requirements pertain to the THX picture mode; the manufacturer may choose different settings in other picture modes.

  1. 1. Rec. 709 Standard. THX restricts the color gamut to Rec. 709 as all source material is mastered to these limits. The display must measure within ±0.005 of the coordinates listed below for white, red, blue and ±0.010 for green coordinates (Sec. 3.1.5)
Color Rec. 709 Chromaticity**
x y

White

0.313

0.329

Red

0.640

0.330

Green

0.300

0.600

Blue

0.150

0.060

Cyan

0.225

0.329

Magenta

0.321

0.154

Yellow

0.419

0.505

 

  1. 2. Panel Reflectance. THX requires a panel reflectance of <2% to ensure good contrast in a moderately lit viewing environment, which keeps the image dark the presence of  lamps. (Sec. 3.1.12)

 

  1. 3. Uniformity. THX measures the uniformity by comparing eight locations at the edge of the panel to the center. THX mandates that black and white panel uniformity must be >80% in luminance and within ±0.004 in color. (Sec. 3.3)

 

  1. 4. Four-point viewing angle (LCD flat panel). THX compares the color and uniformity at 45º to the on-axis (90º) measurements for a color of ±0.004 and uniformity >75%. (Sec. 3.3.5)

 

  1. 5. Image Retention Recovery (Plasma panel). THX ensures that the image recovery utility within the panel eliminates image retention. A static checkerboard pattern is displayed for two hours. The retained image must recover >98% within ten minutes. (Sec. 3.3.7)

 

  1. 6. Overscan. The native 1920 x 1080 source must be presented pixel-for-pixel with no overscan. This ensures that no scaling artifacts are added to the image. (Sec. 4.2.4)

 

  1. 7. Video Processing. THX uses proprietary patterns to evaluate the following: judder, deinterlacing, bob and weave switching time, contouring; jaggies (smoothing), etc. (Sec. 4.0)

 

The requirements described and others within the THX Display Specification are incorporated in the THX picture mode. In addition, THX engineers choose the default settings of the manufacturer-specific features (noise reduction, interpolation, contrast enhancement, etc.).

 

THX Mode

In addition to the performance testing, THX requires implementation of a THX Movie Mode, with performance characteristics determined by THX after the display is completely characterized.

The THX Movie Mode has specific settings for gamma, color point, luminance, overscan, and other settings specific to the certified display. This setting is intended to provide the optimum settings for playback of movie titles, but can be used for viewing other content as well.

 

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What Does THX Do For You?

THX certification assures buyers a high quality high definition display. TV makers can’t pass the rigid specifications by using low quality LCD or plasma panels and/or mediocre signal processors.

Engaging the THX mode assures HDTV purchasers a simple “out of the box” setting that is as accurate as you will find, without any other adjustments or extra cost post setup calibration.

We’ve tested THX Certified modes in various brand sets and confirmed they measure close to industry image setting standards. While it’s possible that an HDTV manufacturer can do their homework and produce a factory setting that provides the best possible picture quality, to date no vendor does. THX certification is available on select LG LED LCDs including the 47LE8500], and LG plasmas :50PK750, and 60PK750, Panasonic plasmasTC-P42G25, TC-P46G25, TC-P50G25, TC-P54G25, Epson front projectors, Runco front projectors and JVC front projectors. Here is a link to all the 2010 THX Certified models.

Bottom Line

If you want an accurate HDTV image, choosing a THX Certified display will get you a top quality unit without fuss. THX Certified displays continue to receive some of the highest ratings from the leading magazine and web HDTV reviewers.

Edited By Michael Fremer

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