Panasonic TH-50PZ800U Plasma

I have been looking forward to calibrating one of the new Panasonic 800Us. These sets stand out from the rest of Panasonic's current line of plasma TVs by the inclusion of a THX preset, which supposedly "Faithfully reproduces the image quality that the movie makers intended in order to provide the ultimate cinematic experience at home." In particular, this mode is supposed to offer unparalleled color accuracy, at least compared to Panasonic's other models, which have always been known for exaggerated reds and greens. I own the Panasonic 85U and I can confirm that its red and green primary colors are exaggerated and cannot be adjusted.

What I found was somewhat surprising. There were 3 things about the THX preset that are odd.

• First, you have to enter the service menu to calibrate the white point, and the menu requires you to select both the picture preset and the scan rate (HD or SD). However, there is no THX option available in the service menu! There is, however, a Cinema option, despite the fact that there is no Cinema preset on the 800U. It turns out that the THX preset is just a factory tweaked version of the Cinema preset available on other Panasonic models.
• Second, color accuracy—in terms of the xy coordinates of the primary colors—is only modestly improved by the THX mode, as shown below. Blue is unchanged (it was fine to begin with) and red is improved by a very small amount. Only green is significantly reigned in, and even in this case it remains noticeably over saturated.
  Red: x0.653, y0.330
  Green: x0.293, y0.624
• Third, the real improvements to be had with the THX mode were in color decoding performance. In concert with some modest adjustments to the main Color control, post-calibration the color decoding of the 80U is near perfect. By default, it was something of a horror show, at least in the Standard mode.

Color Performance

This CIE chart shows the improvement available through the THX mode.

What this chart doesn't reveal entirely are the profound improvements in color decoding that this preset brings.

Before
R: + 64%
G: + 2.6%
B: + 82.5%
After
R: -4%
G: + 1.5%
B: + 5.4%

This preset also greatly improved the hue of yellow. Much of the improvement to the hue of cyan is due to improved grayscale tracking, so it is hard to know how much of this can be attributed to THX.

Also, post-calibration, the gray scale tracking was essentially perfect, with an average dE from 20-100% of 1.4. SMPTE recommends no more than 4 dE Lab units for both the white point and the primary/secondary colors for Digital Cinema. The 800U easily meets this standard for the white point, but the primary/secondary colors averaged 6.4 dE, so it misses this mark by a little.

Add the excellent color decoding to the modestly improved primary color chromaticites, and it is fair to say that the THX mode offers significantly improved color performance over the other models in the Panasonic line, though it is still not as good as what is available from the Pioneer Elite or the Samsung A550.

Perhaps the most comprehensive way to represent color performance is to plot the % errors in terms of the three elements of color: lightness, saturation, and hue. The chart below offers a complete analysis of the color performance of the 800U before and after calibration. Notice the large lightness errors in red, blue, and magenta before calibration. This is the color decoding problem I mentioned above.

Contrast and Light Output

In all other respects, the 800U seemed to perform about the same as the 85U. I got a slightly higher black level from the 800U (0.015 fL v. 0.011 fL) than I measured from the 85U, but this small difference may very well just be part of the normal unit-to-unit variation.

Post-calibration, the on/off contrast ratio was 2327:1 @ 34.8 fL peak output. I usually aim for 35 fL peak output, so this was just about ideal. You can get higher contrast in other modes that also offer higher output for brightness freaks. However, these other modes also exhibit MUCH worse color and their gamma is ridiculously low. I measured an excellent 2.24 gamma in the THX/Cinema mode.

As you can see, in the Standard mode, the gamma is something of a mess. Panasonic engineers it this way no doubt to maximize light output. However, though the higher gamma of the THX mode cannot match the peak output of other modes, it nonetheless offers a much more natural image with significantly greater depth.

Sharpness and clarity

Subjective image sharpness is arguably the greatest strength of plasma displays. Plasmas have an ability to create a "window looking onto the world" effect more convincingly than any other display technology. Among the major plasma manufacturers, I have always thought that the Panasonics were marginally better than others at this. Panasonic plasmas are very sharp, with very good 3-dimensionality. The advent of 1080P panels has only improved on this. However, there is one design flaw with the Panasonic panels hat somewhat undercuts this advantage.

Under the Advanced menu, you can select Size 1 or Size 2. Size 2 maps the incoming signal pixel-by-pixel without any scaling. Size 1 scales the image to provide about 3% overscan. Unfortunately, the scaling in Size 1 visibly softens HD images. Consider the photographs below.

Size 1	Size 2

These are two 18.5 and 37.1 MHz multiburst patterns from a 1080i input. As you can see, with Size 1 selected the 18.5 MHz pattern shows some banding, and the 37.1 MHz show significant banding and loss of detail. On the other hand, with Size 2 selected, both patterns are clean and sharp without any artifacts.

This would seem to indicate that Size 2 is the preferred mode. Unfortunately, it is not that simple. Most SD broadcast sources will show video noise along the top edge or sides of the image in Size 2 (the need to hide this is the reason displays generally use overscan). Thus, when watching SD sources most users will want to watch in Size 1 mode. HD sources don't have this problem, which means that ideally users should switch back and forth between Size 1 and Size 2 when going between SD and HD sources. The problem is that the Panasonic remote offers no method for easily doing this. It takes 17 steps on the Panasonic remote to make this switch! Choose your poison.

Subjective Impressions

Having lived with the 85U for several months now, the images we saw from both HD cable and Blu-ray on the 800U looked predictably good—much like the 85U, but with the added refinement and naturalness brought by the increased color accuracy.

The TH-50PZ800U offers an interesting mix of features and performance. It lacks the superb black levels of the Pioneer Kuros and the spot-on color accuracy of the Samsungs. Yet, its black level is better than the Samsung and its color accuracy is significantly better than the non-Elite Pioneers. Thus, the Panasonic 800U is something of a compromise product geared to appeal to a wide range of tastes. This helps to explain why Panasonic does as well as it does in the plasma market. Though the 800U is not the best available in any one area of performance, it nonetheless does very well in a wide range of areas, which explains it excellent image quality and wide popularity.

Since the 800U is only a few hundred dollars more than the 85U, I think that this would be the display to buy for those already leaning towards Panasonic.