Of all the preset picture modes, the TC-P55ST50's Cinema mode looks the best (the Standard mode is surprisingly dark). Be warned that Motion Smoother is now turned on by default in this mode, so if you don't like that soap-opera effect with film sources, you'll want to turn go into the Advanced video menu and turn it off. Black level, brightness, and color are all respectable in this mode, but the Warm2 color temperature is a bit green, and the gamma is too light. You can't adjust either of these parameters in the Cinema mode, which is why I switched over to the Custom mode to perform a more advanced calibration, and was happier with the results. I switched gamma from the default 2.2 to a seemingly more accurate 2.6, I went with the "mid" panel brightness, and I performed some eyeball adjustments to the RGB controls to dial in a more neutral color temperature. After performing these tweaks, I settled in with my usual assortment of BD/DVD demo scenes and HDTV content from DirecTV.
First off, the TC-P55ST50's black level is excellent, which allows it to render a wonderfully saturated image in a dark room. (The GT50 model uses the same Infinite Black Pro panel, while the top-shelf VT50 uses the Infinite Black Ultra panel.) Thankfully, I saw none of the odd brightness fluctuations that plagued last year's Panasonic GT30 plasma. The ST50 produced a deeper shade of black than my reference G25 - not significantly deeper, but deep enough that you could obviously see the difference in a side-by-side comparison. Combine this great black level with very good image brightness, and you get a rich-looking image with outstanding depth and overall contrast. The ST50 certainly isn't LCD-bright and probably isn't the ideal choice for an extremely bright room; however, in my family room with the window blinds open, the picture had ample brightness to produce vibrant HDTV and sports content during the day. The TC-P55ST50 also did an excellent job rendering fine black details, and its overall level of detail with HD sources was very good. Beyond the mildly green color temperature that I was able to correct, I had no issues with the TV's color performance. All of the color points looked close to reference standards, and skin tones were neutral (more natural-looking than those of the G25, I might add).
Motion blur isn't really a concern with plasma technology, but I ran through the motion-blur tests on my FPD Benchmark BD anyhow. The TC-P55ST50 cleanly rendered all of the motion-blur patterns and did not exhibit the occasional ghosting effect I see with 120Hz/240Hz LCDs. With Motion Smoother disabled, the TV produced clean lines to HD720 in the Resolution test pattern. With Motion Smoother enabled, the lines were clean to HD1080. The difference was small enough that I was content to leave Motion Smoother turned off, since I don't like its smoothing effects with film sources. I will say that the Weak Motion Smoother mode is subtle enough to be tolerable. In other processing news, the TC-P55ST50 passed all of the 1080i tests on the HD HQV Benchmark BD, and I did not notice jaggies or other artifacts with real-world 1080i signals.
For my 3D tests, I ran through my standard demos from Ice Age: Dawn of the Dinosaurs (Chapters 3 and 9), Monsters vs. Aliens (Chapters 12 and 13), and Monster House (Chapters 6 and 7), plus assorted DirecTV 3D content. Like its 2D counterpart, the TC-P55ST50's 3D image has excellent contrast and rich color. The 3D depth was impressive, and the level of detail was very good with both Blu-ray and DirecTV content. Light output was good for HDTV and movie-watching in a medium to dark room, but I found the Cinema and Custom modes to be a little dim for a bright daytime environment (the Game 3D mode is a slightly brighter alternative). In last year's GT30, I could crank up the light output by setting the panel brightness to high in the Custom mode; this year, that change seemed to have little effect beyond slightly altering the color temperature. In terms of 3D hardware, the lighter TY-ER3D4MU glasses are much more comfortable to wear for an extended period of time.
The TC-P55ST50's image was sometimes noisy in darker scenes. The new GT/VT models reportedly have 24,576 steps of gradation, while the ST models have about half that, or 12,286 steps. (The UT/XT models drop to 6,144 steps.) When I put up the DVE gray-scale ramp, the transition from light to dark was not smooth; I saw more uneven steps than I've encountered on any recent TV I've reviewed. With real-world sources, that sometimes translated into noise, uneven transitions from light to dark, and color shifting in grays. Two of my favorite gray-scale demos are Chapter 10 in the Ladder 49 DVD (in which Joaquin Phoenix moves through a dark, completely smoke-filled room) and Chapter 5 of the Flags of Our Fathers BD (in which the soldiers sit on the ship's deck on a dark, foggy night). Both scenes exhibited color shifting in their grays. Interestingly enough, the new ST50 exhibited slightly less color shifting than the older G25; however, in certain dimly lit scenes from House on Fox's HD channel, the newer model revealed more noise and uneven gradations in backgrounds. By comparison, my living-room LCD (the Samsung LN-T4681) produced a cleaner picture in these same scenes. The lighter gamma in the ST50's Cinema mode also contributes to the problem, making low-level noise more obvious in darker areas of the scene. I was able to lessen the visibility of the noise in the Custom mode by setting a darker, more accurate gamma. I also upped the noise reduction to strong, which helped but didn't completely solve the problem. This wasn't an ever-constant issue with all sources, but I did see more noise than I'd prefer.
The TC-P55ST50's handling of SD content is average at best. Upconverted images looked a little soft, and the TV was somewhat slow to pick up the 3:2 cadence in film sources, so I noticed jaggies and moire in my demo scenes from Gladiator and The Bourne Identity. The TV also failed to detect most of the assorted cadences on the HQV Benchmark DVD. For the best performance, you might want to let your source devices or an external processor handle the upconversion process.
The Infinite Black Pro panel effectively reduces glare off the screen while allowing blacks to look darker during the day; however, it's still a reflective screen, which can present problems when trying to watch darker content in a well-lit room. Be mindful of the position of lamps and other light sources in relation to the TV.
With 3D content, I was surprised by the amount of crosstalk I witnessed - surprised because, in my experience thus far, plasma does the best job of keeping crosstalk to a minimum in active 3D displays. That's not the case here. I wouldn't say the TC-P55ST50's crosstalk is excessive, but it occurs with enough consistency to earn it a mention here. Also, Panasonic has opted not to include any 3D glasses with the ST50. While the $80 asking price of the TY-ER3D4MU is lower than previous glasses, it still adds up if you want to buy glasses for multiple family members.
In my book, you still can't beat plasma when it comes to getting the best combination of features, screen size, and performance for the price, and Panasonic has set the 2012 bar high with the new TC-P55ST50. This 55-inch plasma TV currently has a street price around $1,550; a similarly equipped model in the LED camp could cost you $1,000 more than that. There's also the not-insignificant fact that the TC-P55ST50 serves up a very attractive HD image, with an excellent black level, good brightness and detail, and natural color. If you're shopping specifically for a 3DTV, you can find better 3D performers on the market, but the TC-P55ST50's 2D performance is excellent.
I must add, though, that I'm intrigued by the step-up TC-P55GT50: It costs about $350 to $400 more than the ST50 (still a good value at this screen size), but it adds THX certification, the 24,576 gradation steps, the dual-core processor for multitasking, and more connection options. While I have not yet reviewed the GT50, its THX mode could mean a better-looking image right out of the box with little to no calibration, and the higher gradation number could mean less digital noise. It's at least worth a comparison of the two models to see if you find any potential performance improvements to be worth the step up in price.