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We were impressed by the JVC LT-32P679's black level, but the peak brightness was not as impressive. Whites and black held up well, but the HDTV seemed to be doing some kind of background processing that led it to simply fail our greyscale gamma test.
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Black Level (7.60) 
The black level of an HDTV is very important as it will contribute to realistic images with deep blacks and is a key contributor to contrast level. We measured the black level on the JVC LT-32P679 at 0.12 candelas per meter squared (cd/m2). This is a very good score for an LCD HDTV, which don't do as well on this test as Plasmas. The reason is that LCDs produce black by blocking light from their backlight, and they can never get it all, whereas Plasma TVs can actually turn off the light they emit for each pixel individually. Still, as we said, we were very pleased with the JVC LT-32P679's black level given its an LCD HDTV. It should produce deep blacks.
Peak Brightness (7.21)
This is the converse of black level, for peak brightness we are looking at the brightest white that the JVC LT-32P679 can produce. We measured peak brightness at 218.42 cd/m2. This is not very bright, especially for an LCD HDTV, which often produce peak brightness above 300 cd/m2. The JVC LT-32P679's poor peak brightness is directly related to the compromises we made in our calibration, which you can read about in our Performance: Summary section. If you wish you can get the JVC LT-32P679's peak brightness all the way up to 390 cd/m2, but this will seriously impact the HDTVs ability to produce accurate images on the screen. As it is the JVC LT-32P679's brightness level may not be impressive, but it is right about the 200 cd/m2 that we consider ideal for most conditions, so it shouldn't be too much of an issue.
Contrast (7.04)
Contrast is the ratio between the brightest white and the deepest black. The JVC LT-32P679's contrast ratio was 1820:1. This is about average, we've seen signficantly worse from other HDTVs, but we've also seen better. In this case the JVC LT-32P679 was helped out by a very good black level, but hurt by the less than impressive peak brightness. The end result is a reasonable score, but nothing that overly impressed us. One thing we should note is that if you compare our contrast ratio to the ones published by manufacturers you'll see a significant difference. The reason is that manufacturers tend to cheat by comparing the brightest white with settings pushed to maximum and the deepest black with the backlight completely off. Since doing either of these things will ruin your viewing experience we don't use this method. Instead we look at the contrast ratio based on calibrated settings that are meant to produce the best picture for the viewer.
Tunnel Contrast (9.84)
Black level and peak brightness are all well and good, but the reality is that black and white don't tend to exist by themselves on a real HDTV. As such we look at what happens to blacks as more of the screen is taken up by white in our tunnel contrast test. Ideally the black level should stay constant regardless, and this is exactlly what we found on the JVC LT-32P679, as you can see below.
The black level stayed relatively constant no matter how much white we put up on the screen. This is excellent to see and will ensure that you should get deep blacks no matter what else is on the screen.
White Falloff (9.33)
This is the converse of the previous test. Here we look at what happens to peak brightness as we put more and more black on the screen. As with our Tunnel Contrast test we were impressed at how well the JVC LT-32P679 held up here as the white level only deviated by a single candela per meter squared no matter what we did to the amount of black on the screen. You can see this indicated more clearly by the chart below. That flat white line is exactly what we want to see, and its what we got with the JVC LT-32P679.
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Uniformity (6.0)
Ideally an HDTV will stay smooth and uniform when displaying black or white. We found that the JVC LT-32P679's had a few problems in this area, however. With a white screen we noted some dimness at the corner and a few scattered blotches of dim areas. These are not overwhelmingly obvious but are apparent when looking at an all white screen. We saw less blotchiness with an all black screen, but we also saw some significant brightening at the edges and corner of the display. It could be worse, but it also could be significantly better.
Greyscale Gamma (2.08)
Update: We have rescaled our scoring system for this test, the original score was 0.0
The JVC LT-32P679 basically failed this test. The greyscale gamma curve maps what happens as the display goes from black to white. Below is the graph of the JVC LT-32P679's performance in this test. Ideally the curve should run right along the blue line, smoothly shifting across the greyscale. You can see quite clearly that the JVC LT-32P679 did not follow this curve, instead deviating significantly.
The chart above takes the curve and plots it exponentially since our eyes tend to notice exponential differences rather than discrete levels. Below you can see the actual Gamma curve. Ideally this curve should be slightly concave and completely smooth from top to bottom. You can see that instead it's bumpy with almost no concave near the top.
What this means in practice is that the JVC LT-32P679 is very unpredictable as it makes changes from black to white. Change does not occur smoothly and occasionally you'll have sudden jumps. This is likely due to the same problem we saw when calibrating the HDTV. There seems to be some kind of dynamic adjustment betwen the blacks and whites that can't be turned off. The result is a zero in this section.
Resolution Scaling (7.27)
With the plethora of different video formats that are fed to an HDTV its important to see how it handles these different signals. The JVC LT-32P679 did a reasonable job with all three of the non-native formats we fed it, with the significant issue that we saw overscanning in all cases. In fact we saw the overscanning even at the native 720p resolution, and there's no way to get rid of this. What this means in practice is that you're going to lose between 4-5 percent of a picture both vertically and horizontally, a serious problem.
480p (7.8)
480p is the resolution used by standard definition television and DVDs. Feeding the JVC LT-32P679 a 480p signal text was clearly visible and resolution was good, but we did notice that we lost about 4% both vertically and horizontally to overscan.
1080i (6.75)
Most broadcast HD television comes through in 1080i resolution. For a 720p HDTV like the JVC LT-32P679 such a signal needs to be downscaled to fit on the resolution of the HDTV. The effect was that text was only legible at 10 point font or above, below that it became so small and crammed together it was difficult to read. Resolution was good, but we did notice some interlace effects that created some banding and colors in our moire pattern test. We also saw the same overscanning problems that the HDTV is plagued with as we lost about 5% of the signal both vertically and horizontally.
1080p (7.25)
Also known as "full" HD, 1080p signals are currentliy the best quality video you can get and generally are only available from Blu-Ray discs. As with a 1080i signal the JVC LT-32P679 needs to downscale it since it is a 720p HDTV. We saw the same issue with text being legible at only 10 point as we saw with the 1080i signal, but did not notice the banding and slightly green cast on the moire patterns. We did lose about 5% of the signal both vertically and horizontally, however.
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