Vizio SV471XVT HDTV Review - Color Accuracy |
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Published on July 22, 2009 Comment on this |
Color Temperature (9.04) As part of our calibration procedure, we set the white of the HDTV being tested to as close to 6500k as possible. For the SV471XVT, the closest we were able to get was about 6100k with the Normal white balance setting. This is with a white screen at the brightest white, but we also test how well this color temperature holds up as the whites shift into greys. On some HDTVs, we see the color temperature of the greys change, which can create a color cast. That's why we test this, and the graph below shows how the color temperature changes as the intensity of the whites decreases. On an ideal display, there would be no shift; the line on the graph would remain completely flat. The SV471XVT isn't perfect, but it is pretty good; although there is a distinct shift in the color temperature upwards as the intensity decreaes, this is not by any significant margin; the change remains small across the entire range that we test.
The real-world impact of this result is that you might spot a very subtle bluish cast to some greys, particualrly the darker ones. But this won't be that distracting, and most users probably won't be able to see it, even if they try.
RGB Curves (7.71) Like all HDTVs. the SV471XVT creates colors by mixing the primary colors of red, green and blue. To do this accurately, the display has to be able to create the different intensities of each color, which is what we test here. We feed the display a signal that contains all of the different levels, and measure how this translates into the color on the screen. Then, we create the graph below, which shows this translation. An ideal display would have a perfectly smooth curve here; every small increase in the input signal would translate into a similar increase in the intensity of the color. However, we seldom see a smooth curve because the internal processing that the display does causes bumps and jumps in the response. The SV471XVT had a few issues here; the red curve in particular was somewhat bumpy.
If we take this data and convert it into a gradient, we see how these bumps translate into banding on a gradient. The effect of these bands is that subtle color changes (such as skies or the details of flowers) may not be accurately represented: they may look flat, or may show bands that weren't present in the original image. The top gradient represents the ideal; a perfectly smooth response. If you see bands or bumps in this, they are caused by the display you are reading this review on.
Color Gamut (6.45) The color gamut of a display is the range of colors that it can show. The range of colors that a HDTV signal contains is set in a standard that was defined by a group of international experts (it is called the ITU Recommendation 709, or Rec.709), so an ideal HDTV should be able to reproduce exactly the same range of colors as the standard. That's what we test here: we measure the color coordinates of the red, green and blue and see how close they come to the standard.
As you can see from the graph above, the SV471XVT had a few issues here; the red was almost perfect, but both the blue and the green were somewhat off, meaning that both greens and blues will look a little different to what the program maker intended. These differences aren't huge, but they are enough to be noticeable.
Most of the HDTVs that we have reviewed have some sort of problem here, and the SV471XVT isn't much worse than most. It's also not much better, though.
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• Whites were very clean and accurate
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