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Panasonic TX37LZD85 Calibration

by David Mackenzie
24 May 2008

Greyscale

The Panasonic TX37LZD85's Colour Balance control allows the user to select from Cool, Normal or Warm colour temperatures, which tinted the picture blue, green, and red, respectively. Out of the three settings, the "Warm" preset was closest to the D65 greyscale standard which film studios adhere to, and brings the most accurate picture. That said, with the CCT chart indicating that the temperature was closer to 6000K than the desired 6500K, it's still not ideal. Below are the RGB Levels and Colour Temperature charts for the "Warm" setting:

RGB levels

CCT

Sadly, there are no user-accessible Greyscale calibration controls on this LCD television. In other words, calibrating the greyscale for a truly accurate picture will require the user to either enter the hidden service menu (and accept that there may be potential warranty issues attached) or hire a professional to do the same. As doing so would invalidate our review sample agreement with Panasonic UK, we were unable to refine the greyscale performance of the TX37LZD85 LCD HDTV further in this case, although it's not necessarily an impossibility.

Colour

CIE

As with most HDTVs, the Panasonic TX37LZD85 does not have a mechanism by which the user can alter the setup of colour decoding. But, this wasn't a problem, because the CIE chart showed that the points for all six colours were very, very close to Rec.709 standards anyway. Red was pushed slightly towards purple, but this wasn't too noticeable in real world material.

This LCD TV has an option called "Colour Management" in the Picture menu, which is a simple On/Off toggle. Turning it on does almost nothing, and really only shifts Cyan marginally.

Benchmark Test Results

Dead pixels None
Screen uniformity Excellent
Overscanning on HDMI 0% with [Picture Overscan] turned Off
Blacker than black Passed
Black level Average
Black level retention Stable if [Viewing Mode] set to Cinema or Eco
Primary chromaticity Very good
Scaling Very good
Video mode deinterlacing Effective jaggies reduction
Film mode deinterlacing Failed 3:2/ 2:2 cadences in 480i/ 576i
Viewing angle Excellent for an LCD TV (120-130°)
Motion resolution 600
Digital noise reduction [P-NR] function only cuts off frequencies, no control over Temporal Noise Reduction which is on at all times
Sharpness Non-defeatable edge enhancement
1080p/24 capability (PS3) Accepts 1080p/24 video signal; no telecine judder
Input lag 30ms slower than a CRT monitor

Black Level

Calibrated black level on the Panasonic TX37LZD85 measured 0.33 cd/m2, which was about average for an LCD TV. As the TV does not feature a manual Backlight control (at least not without delving into the service menu), it wasn't easily possible to improve this figure further, unless the "Dynamic" or "Normal" picture modes were selected. These modes both activate the Auto Contrast system, which intelligently raises or lowers the backlight brightness to acheive maximum contrast ratio ("Cinema" and "Eco" modes leave this feature disabled). However, this feature relies on the user's ability to tolerate fluctuations in screen brightness, so isn't for everyone.

Screen/Backlight Uniformity

In addition to excellent viewing angles, screen uniformity has always been a strong point of IPS Alpha panels. As a result, I wasn't surprised to find that the Panasonic TX37LZD85 had no significant clouding/ mura defects visible, despite the higher than optimum backlight brightness - an excellent result.

Static Resolution

With "Picture Overscan" turned off and a 1080p source fed to the Panasonic TX37LZD85, the LCD HDTV correctly enabled 1:1 mapping. However, due to the fact that this television employs non-defeatable edge enhancement, distortion in the form of ringing was visible around high frequency details on the SMPTE 133 test pattern. This means that genuine picture detail is slightly compromised.

Motion Resolution

The "FPD Benchmark Software for Professional" Blu-ray Disc allowed us to see how the LCD TV handled motion. This is perhaps the most impressive area of the Panasonic TX37LZD85, as the motion test pattern indicated that it could resolve around 600 lines of horizontal motion. By contrast, LCD televisions which don't use some sort of motion interpolation technlogy typically only manage around 300.

Video Processing

Unfortunately, the LCD TV's video processing actually suffers from the Chroma Upsampling Error, which means that the edges of bright colours appear slightly jagged upon close inspection, but only when Interlaced material is input. Fans of animation or other content which is typically saturated, will want to use an Upscaling DVD player (making sure that it is also free of the problem!) to sidestep this error.

The diagonal interpolation capabilities of the Panasonic TX37LZD85 were very good. Almost no jaggies crept through at all using the Silicon Optix "rotating bar" test, and real world results were similarly free of the problem.

For PAL film material, the LCD HDTV did not detect the 2:2 cadence. This means that for optimum results, users will need to connect an Upscaling/Progressive Scan DVD player that does. More surprisingly, the Panasonic TX37LZD85 did not pass the "Film Detail" or the 3:2 cadence tests on the NTSC version of the Silicon Optix disc. This isn't of consequence to most of us here in the UK (where the PAL system is used), but it is very surprising because most video processing devices can pass these easier tests. In fact, this means that the Panasonic TX37LZD85's internal video processing has no Film Mode detection capabilities whatsoever.

This is less of a problem now that DVD players perform Deinterlacing internally, but remember that films broadcast on TV or output from devices such as standard-def satellite or cable decoders, or older DVD players, require the television to perform cadence detection and will suffer as a result. You will definitely need to connect a capable progressive/upscaling DVD player for the best results. 

There are other problems related to video processing on the Panasonic TX37LZD85 that would appear to be deliberate design decisions rather than accidental errors. Firstly, although there is an option labelled "P-NR" in the Picture menu, this TV still has some degree of temporal noise reduction working at all times, which can't be disabled and causes details in some films to smear. Secondly, the 100hz Motion Picture Pro system can't be disabled. It might seem counter-intuitive to pay for a TV with this feature then want to disable it, but the fact is that as a motion estimation system, it can still create artefacts (they were particularly noticeable during fast motion and animated content). That said, the motion artefacts were much rarer than they were on last year's TX-32LXD700, so it would appear that Panasonic has improved the algorithm.

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