LG 50PB6600 Plasma TV Review
Shallow black levels devastate this plasma's picture quality.
Behind the Screens
LG's 50PB6600 plasma TV (MSRP $699) didn't bomb every test we threw at it, but it bombed the one that matters most: black level. That's as unfortunate as it is inexplicable. Why on earth make a plasma TV—a technology most loved for its depthless, inky black levels—if it can't even get as dark as an edge-lit LCD?
Whatever the case, the PB6600's deplorable contrast performance absolutely ruins this TV's chance for a good score—despite great color, motion, and viewing angle results.
We believe it's important to tell you two key things about every TV we test: how well it performs straight out of its box, and how well it's capable of performing with some informed calibration. To get you this information, we run tests, collect data, and score each TV prior to calibration.
Afterwards, we calibrate each TV (ITU standards) to find out what its full potential really is. Unfortunately, no amount of calibration can repair a shallow minimum luminance level, so the LG PB6600 plasma TV's fate remains sealed—with or without calibration.
Nevertheless, I went about fine-tuning this LG's color, gamma sum, and grayscale for good measure. Starting in the display's "Cinema" mode, I altered its gamma, raised its backlight slightly, and made adjustments to primary and secondary colors in its CMS, as well.
The fact that every LED LCD panel we've tested this year earned a better score on black level than this LG plasma really says it all. How did this happen? The black level and average peak white are so poor that the overall contrast ratio is 193:1. That's insanely terrible. A contrast ratio of 1000:1 is below-average, 193:1 is bordering on unheard of.
The PB6600's average peak white level of 54 cd/m2 is dim even for a plasma display, and its grayish black level of 0.28 cd/m2 is just hopeless.
This LG isn't completely a "non-plasma" plasma. Since this technology requires no backlight, light travels a shorter distance before reaching your eyes—and shorter distance means less opportunity for light to scatter and dissipate, resulting in a killer total viewing angle of 166º.
So from just about angle, the image won't notably degrade. Too bad the image quality is so poor to begin with.
The LG PB6600 handled the color gamut test with ease. When we test this performance aspect, we're determining how close to international standards a TV's color production is.
Though its primary colors aren't flawless, this LG still does a standup job on this test. The only notable troubles impacted its secondary colors (cyan, magenta, yellow). Luckily, this plasma comes equipped with the necessary controls to nearly perfect its color performance.
For TVs, there are different ways to ramp up out of total darkness into grays, and up to white levels—and the gamma sum illustrates a panel's chosen ramp-up behavior. Some televisions ramp up too quickly, others erratically, others very slowly.
To score this performance, we measure against an ideal, dark-room gamma sum of 2.4. I ran a test to see what the LG PB6600 was up to and found that it had a gamma sum of 2.27. By altering its gamma in the Expert Menu, I got this panel a bit closer to the home-theater ideal—with a final gamma sum of 2.34.
Grayscale & RGB Balance
A common problem we see in TVs is that black, gray, and white values sometimes carry unwanted tinges of color—bluish highlights, reddish grays, and so forth.
To test this performance aspect, we measure the total error within the grayscale (DeltaE) and we look at how the TV balances its red, green, and blue sub-pixels.
In the case of the PB6600, I noted overemphasis of the blue sub-pixel throughout middle to high steps of the grayscale (50 IRE to 100 IRE). The result is that middle grays and bright whites can sometimes appear a bit blueish. On the whole, grayscale error amounted to 8.42 DeltaE—that's well above the acceptable upper limit we look for (DeltaE 3). Happily, some simple calibration lowered the LG's error to a more acceptable total of 2.16.
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