JVC LT-42WX70 LCD HDTV Review - Blacks & Whites

Blacks & Whites Summary
• Decent black levels and peak white. • Problems with uniformity; blotchy black screens and paler whites on the bottom • Good Gamma control
	Calibration	Page 4 of 18	Color Accuracy

Black Level (8.0)

The lower the black level, the deeper the black will look on screen. The LT-42WX70 had decent performance here; we measured the depest black at 0.1 cd/m2. That's about the same as the Sony Bravia KDL-52V5100, but is somewhat better than the other JVC we have reviwed, the LT-42P300. Deeper blacks means a wider contrast ratio and more dramatic images, so this is a good thing to see.

Black Level

Peak Brightness (8.23)

At the other end of the scale is the peak brightness; the brightest white that the display can manage. The LT-42WX70 managed a very creditable 331 cd/m2 here, which is one of the higher numbers that we have seem. This would be particularly advantageous if you were watching TV or looking at photos on this screen in daylight; the brigher the screen, the better it will look.

Peak Brightness

Contrast (8.23)

The ratio of the darket black to the brightest white is the contrast ratio, and the bigger this is, the better the on-screen images will look. We found that the LT-42-WX70 had a contrast ratio of 3317:1, which is in the middle of the pack. It's not the best contrast ration we've seen, but it also far from being the worst, and it means decent image quality.

Contrast

One thing to note here: our numbers differ from the ones that the manufacturers quote because they measure the deepest black with the backlight turned down, and the peak white with it turned up. Our measurements are done with the backlight set at the highest level for both, because that's what happens when you are actually using  the TV. So, our figures represent what you get in the real world, and the manufacturers figures don't.

Tunnel Contrast (9.85)

Your TV doesn't ge tthe luxury of diaplying just blacks or whites very often; in most situations, it has to display both at once. What we test here is how dark the black remains when there is white next to it; does the black stay nice and dark, or does light bouncing around inside the screen cause it to turn greyish? We didn't see a big problem here with the LT-42WX70; even when showing just a small area of black surrounded by white, we found that the blacks remained at pretty much the same level.

Tunnel Contrast

White Falloff (9.96)

The flip side of this coin is what happens to the whites when they are surrounded by black. So, we test this by measuring the brightness of a small area in the middle of the screen with varying amounts of black surrounding it. Again the LT-42WX70 performed well here: we found that the whites remained at a pretty constant level irrespective of how much black was around them.

White Falloff

Uniformity (4.88)

The LT-32WX70 had some serious issues in this test, where we look at how uniform the screen looks. We test this by displaying both black and white screens and examining them to see how uniformly dark and white the screens are. On the black screens, we saw several large blotchy areas on the screen that were much lighter than the rest, which could distract from the image if you are watching a horror film or something else that relies on areas of black for dramatic impact. On our tests using a white screen, we also saw problems where the bottom edge of the screen was significantly darker than the rest of the screen. Again, this was bad enough that it could prove distracting when watching TV.

Greyscale Gamma (9.0)

The LT-32WX70 is unusual in providing the user with access to a number of different gamma settings, called Gamma Mode 1 to 6. We found that Gamma Mode 3 was pretty much right on the mark for what we look for; we measured the gamma here at 2.19, just a touch off the 2.2 ideal level that we look for. The Gamma curve was also pretty smooth, although there was some issues with stepping; the stair-steps on the graph below are where an increase in the signal didn't lead to a similar increase in the luminance of the screen, which could lead to banding issues on the screen, where a subtle change in the grey level is reproduced as a sudden jump.

Greyscale Gamma

Resolution Scaling (7.75)

The LT-42WX70 is a 1080p display, but it still has to deal with lower resolution signals that a device such as a DVD player or cable box could throw at it. So, we test every display with each of these signals, examining ho well it deals with the process of upscaling these signals to fit the screen.

480p (7.95)
With a 480p signal such as one produced by a standard definition DVD player with a HDMi output, the LT-42WX70 did a decent job of upscaling the resolution cleanly; we saw clear text and as sharp edges as you would expect. The signal was overscanned by about 3%, so the edges of the image are cropped off, and there is no way to overcome this. But that's a pretty standard approach, and shouldn't be a big issue for most users.

720p (8.0)
Signals like this are often used by broadcasters when showing sports; the progressive nature of the signal makes fast movement look better. A 720p signal on this display looked decent; we saw sharp text, but there were some problems with clise-knit patterns of lines producing an interference effect that wasn't consistent across the screen. So, if your favorite sports presenter had a fondness for herringbone patterned sports jackets, you might see a somewhat unpleasant wavy lined effect. The screen also defaulted to the full aspect mode, which somewhat confusingly added about 3% overscan to the image, so the edges of the iamge were cropped off the screen.  this could be a pain if you connect a computer that outputs a 720p signal, as you'll loose the menu bars at the top and bottom of the screen. This can be easily overcome by using the Full Native aspect mode, though, and putting the PC into the monitor preset mode defaults to no overscanning.

1080i (6.3)
The LT-42WX70 did a less impressive job of displaying a 1080i signal; we saw some serious problems with odd processing issues that caused some of our test images composed of alternating lines to produce an unpleasant interference effect caused by the display rescaling the image to accommodate a 3% overscan that crops off the edges of the image. Again, this can be overcome by pressing the aspect button on the remote and setting the aspect mode to Full Native, but most displays default to not putting overscan on 1080i signals. The LT42WZ70 doesn't, although there is an option buried deep within the setup screen to change teh default for 1080i/p signals to the Full Native aspect setting. When this was done, the images looked much better; text was sharper and the interference effect was gone.

Compare the JVC LT-42WX70 to other HDTVs
Samsung LN40B650 40"	JVC LT-42P300 42"	Sony Bravia KDL-52V5100 52"