Panasonic TC-P55ST50 3D Plasma HDTV Review$1,699.00
The superb black level on this Panasonic yields a strong contrast ratio, despite the oppressively low peak brightness. It has been a while since we saw a television show images this dimly. However, to be fair, we calibrate in cinema mode, which dims the screen for optimal viewing in darkened rooms, while also producing the most accurate colors and grayscale values. There are other modes that increase the brightness of the screen overall, but they will also affect the picture quality in a way that is less than accurate. More on how we test contrast.
Color & Greyscale Curves
These color curves start out with a slope too shallow, and finish with too much steepness. This means that, in shadow, the detail distinction between values will be low. Objects in shadow will not appear as rounded as they should, rather they will be obscured in blankets of black. On the other end of the spectrum, bright colors will jump up in luminance suddenly, and gradients may show some banding as a result. The bumpy lines are a concern as well. All three lines should be perfectly smooth. Any wavering means an incorrect reproduction of the input signal. More on how we test color performance.
The color temperature showed errors from middle gray, all the way through the darkest images. Picture here will pick up a warm orange hue, but only a slight one. Looking at a gray value scale, from dark to light, you can see where the gray values appear to get a little warm, before they become utterly black. More on how we test color temperature.
The color gamut proved to be incredibly accurate. All three primary colors and the white point almost exactly match the Rec. 709, the international standard set of HDTV colors. The white point shows the most error, but it is very close to dead-on. More on how we test color temperature.
Plasma screens will dim the brightest whites and brighten the black level depending on the images shown on the screen. When there is less white, the whites become brighter, and less black, the black values get brighter. The idea is that when the screen is fully white, the plasma cells are at a high activation, and if they retained such a high peak brightness, there would be a risk of overheating the unit. The black level on the TC-P55ST50 gets significantly brighter when there is very little black on the screen. These small areas of black are surrounded by cells that are at a high activation level, and this high activation in such close proximity can slightly activate the cells that are supposed to be turned all the way off. The brightening of the black level means that the contrast ratio will be highest when there is quite a bit of shadow on the screen, mixed with some bright highlights. More on how we test picture dynamics.