JVC LT-42WX70 LCD HDTV Review - Color Accuracy

Color Accuracy Summary
• The whites were pretty stable • The RGB response was a little • Color gamuts are slightly inaccurate, both for the HDTV standard and the Adobe RGB gamut
	Blacks & Whites	Page 5 of 18	Motion

Color Temperature (8.76)

One of the most important aspects of the color performance of a HDTV is how consistent the whites are. On some TVs, the whites shift as their brightness decreases, so greys start to have a distinct color cast. That's what we test here, but the LT-42WX70 had only minor problems; we saw a slight tendancy for the whites to turn slightly orange in the middle of the range. But this was only a slight shift, and it is only just visible (the green area on the graph below shows the minimum change in the white color temperature that most people will notice).

Color Temperature

RGB Curves (7.58)

Televisions create all of the colors that you see on the screen from a combination of the red, green and blue elements that form the dusplay, so it is important that these colors are accurately reproduced; if a display fails to accurately create subtle changes in these primary colors, the colors that the combinations create won't look accurate. We test this by sending the display a range of intensities of each of the primary colors, and measuring the color on the screen. The graph below shows the results; with a perfect TV, these lines should be smooth curves. On the LT-42WX70, they are some way from being perfect; the lines are extremely bumpy.

RGB Curves

What this means in real terms is that subtle color changes may not be accurately reproduced, so things like blue skies and plants may look flat, with sudden abrupt jumps rather than the subtle color changes that exist in the real world.  You can see this in the charts below, which show what a red, green and blue gradient would look like on the display. The Ideal Response should look smooth: if there are sudden jumps or glitches in this, the device you are reading this review on has a poor response curve.

Red Response Comparisons
Ideal Response
JVC LT-42WX70
Samsung LN40B650
JVC LT-42P300
Sony KDL-52V5100

Green Response Comparisons
Ideal Response
JVC LT-42WX70
Samsung LN40B650
JVC LT-42P300
Sony KDL-52V5100

Blue Response Comparisons
Ideal Response
JVC LT-42WX70
Samsung LN40B650
JVC LT-42P300
Sony KDL-52V5100

As you can see from this, the LT-42WX70 has a far from ideal response; the gradient on all three of the colors is not smooth and there is some quite significant banding across the range of shades.

Color Gamut (5.14)

The range of colors that a display cam represent is called the color gamut. This is one area where the LT-42WX70 differs greatly from most TVs; it claims to support several different color gamuts, including the sRGB and Adobe RGB color gamuts used by many digital cameras. But the first thing it has to support is the standard HDTV color gamut, which is defined by something called Rec.709, where a group of color experts defined what colors a HDTV image could contain. If a HDTV matches this reccommendation, the colors on the screen will look the same way that the filmmaker intended.

Color Gamut (Rec.709)

The LT-42WX70 did rather por job here; when the TV is set to the Normal Color Space setting, the measured color gamut is some way off from the reccomended one, with both the red and green corners of the gamut being further out than they should, which means that the reds and the greens will look a little oversaturated.

For those who like to look at the numbers, the measurements we made are below.

Because the LN-42WX70 also claims to support the Adobe RGB color space, we also tested it to see how well the display represented this wider color space.

Color Gamut (Adobe RGB)

As you can see from the diagram above, the LN-42WX70 covers most of the gamut, but doesn't quite manage all of it; it falls somewhat short in the green area. If you look closely at the specifications for this display, they state that it covers 96% of the Adobe RGB gamut, and the missing 4% seems to be in the greens.

What is this likely to mean for the serious photographer that the display is aimed at? Well, the Adobe RGB color space mode definitely has a wide color gamut than a standard TV, so if you shoot photos in the Adobe RGB color space and use this monitor in that same color space, your colors will look closer to the original than they would on a standard HDTV. But they won't be as accurate as a professional monitor that covers the entire Adobe RGB color gamut and more, especially with greenery.

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