LG 47LH90 LCD HDTV Review - Blacks & Whites |
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Published on October 19, 2009 Comment on this |
Black Level (5.10) Black level is one of the indicators that a TV has good detailing during dark scenes; if it isn't capable of a low black level, your blacks and going to be unnaturally bright and washed out. Typically LCDs have issues with this test, because they depend on backlights. Plasmas can usually display much deeper blacks, the tradeoff being dimmer whites. Even compared to other LCDs, the 47LH90 didn't do particularly well on this test. The "good" range for black level is 0.1 candelas per square meter (cd/m2); around there is great, below there is golden, but once you get towards 0.2 cd/m2, you start to wander towards washed out blacks. Unfortunately, the LG 47LH90 is capable of 0.38 at its lowest. The 47LH90 does have a localized dimming feature, but we don't see much of a difference between it and a regular dynamic backlight. When it worked, it washed out the subtle details in the area. It typically meant the difference between someone's black suit looking like a suit and that same suit looking like a flat swath of black. We weren't too impressed with the feature.
Peak Brightness (9.78) Peak brightness is an oft-overlooked facet of picture quality. A low peak brightness can hurt your contrast ratio, lead to external lights washing out the screen, or otherwise reduce the level of detail in your picture. LCDs have the advantage on this test, since their display technology essentially hinges on shining a bunch of flashlights at your face. Plasmas have issues here because they draw too much power to display large areas of white at a high luminescence. The 47LH90 did very, very well on this test. Typically all you need for a decent picture is 200 cd/m2, with anything above 300 cd/m2 being gravy. The LG 47LH90 exceeded both these benchmarks with a stunning 456 cd/m2. Due to the logarithmic progression of the greyscale, 0.1 cd/m2 in the dark end can mean the same difference as 100 cd/m2 in the bright end. While this means the 47LH90 isn't a mind-blowing magnitude greater than a 300 cd/m2 TV, the difference will be noticeable. You shouldn't have any issues with the 47LH90 getting washed out by external light; if your 47LH90 is having brightness issues, your set is either defective or the majority of other TVs out there will be having the same issue.
Contrast (6.32) Contrast is extremely important, because our eyesight is based on contrast. We have trouble seeing subtle differences, so to keep up a level of detail we're capable of perceiving, a TV has to be capable of a high level of contrast. The LG 47LH90 had a great brightness with a relatively poor black level, which results in an average contrast ratio of 1201:1. This means the TV will have some trouble catching your eye, compared to the more top-of-the-line TVs. For the average consumer, the difference will be negligible. Chances are, however, if you're reading this lengthy, geeky review, you're not the average consumer. You will notice the difference.
A quick note on contrast: manufactures lie like crazy about this. They'll turn off the backlight when they measure the black, then boost every setting possible to achieve the brightest possible white. Now, this isn't a realistic contrast ratio: since different settings are required for each, there's no way you'd see both levels at the same time during normal viewing. This is why any listed contrast ratio that's more than 10,000:1–and most are over a million to one at this point–are pretty much lying to you.
Tunnel Contrast (9.34) For this test, we start with the entire screen black, then slowly inject a white margin around it until only 5% of the screen is black. Theoretically, this shouldn't have any effect on the TV's black level; the deepest black should remain consistent regardless of how much of the screen the black area encompasses. Of course, the ideal isn't realistic, if only due to normal fluctuations in lighting. What we're looking for on this test, however, isn't those minor fluctuations: we're looking for a sudden drop off, either due to some automatic dim feature or the surrounding white washing out the dark area. The 47LH90 performed well on this test. It didn't have any major issues at all. The largest difference in black levels was full screen vs. 90% black, but even then
White Falloff (9.81) White falloff is the inverse of the above test: instead of a changing black area, however, this test focuses on whites. We're checking for the same phenomena as well. Sometimes plasmas can't produce bright full-screen whites, and sometimes LCDs dim the backlights when they deem the screen to be dark enough. Fortunately, there's not a lot of fluctuation in the 47LH90's brightness levels. This means you won't suddenly lose details when the luminescence of a scene exceeds some arbitrary limit.
Uniformity (8.38) On our uniformity test, we check out a black and white screen and look for imperfections in the screen. Typically on LCDs we see far more issues with the black screen than the white, and the inverse is true for plasmas. We didn't really see any uniformity issues with the LG 47LH90. White screens were almost pristine, as we would have expected. Dark screens were pretty good too, at least ideally. The problem here was a combination of size and display technology. The screen is pretty large, and LCDs have terrible viewing angles; the 47LH90 is no exception. If you were seated directly in front of any given portion of the screen, it'd look perfect; seated dead center, you'd notice the corners appear to leak light like crazy. Again, this has more to do with viewing angle than it does with uniformity, but the end result will be the same for someone seated dead center. Greyscale Gamma (9.39) Greyscale gamma describes how rapidly greys shift to white or black. The ideal is for a logarithmic progression that mimics our own sensitivity to contrast. That way each increment looks identical to the last. We didn't see any issues with the TV's greyscale gamma. As long as you set the TV to a "low" gamma setting, you'll net a textbook greyscale curve. To put our test results in context, when this curve is plotted logarythmically, the ideal curve should have a slope between 2.1 and 2.2. We were able to get a 2.3 out of the 47LH90 when we set the Gamma to "Low." This is just kissing the upper limit for ideal, meaning you won't see any gross inaccuracies in the TV's greyscale gamma.
Resolution Scaling (7.22) Chances are, your TV will be displaying a lot of content that's not within the TV's native resolution. Standard definition broadcast is in 480p, DVDs come in 720p, broadcast HD content runs at 1080i, and Blu-rays use 1080p. Here, we test how well the TV performs showing non-native content. Since these section is the only one where we talk about sharpness, we have to interject a little caveat before we get into the individual tests: the TV has really wacky sharpness. Typically when the sharpness is too high, the TV will create a halo around a color with its inverse. For example, a black bar on a grey screen will suddenly become surrounded by white. Even when we turned both sharpness settings all the way down, we still saw these halos around shapes. When we turned the sharpness up, a second, brighter halo formed inside the initial one. 480p 720p 1080i
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• Very shallow black level unless localized dimming is switched on.
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