MP3 and PVP picture quality: image and picture-quality ratings

The picture quality of any display depends on the saturation of its primary colors and how it controls the brightness of its intensity scale, which is known as the grayscale. The measurements in the first half of Table 3 are discussed in the "Technical information" sidebar.

The grayscale describes how the brightness of the image pixels varies between the black and white extremes discussed in Table 2. If any portion of the grayscale becomes compressed, the images will appear dull and washed out. When the bright end of the grayscale is compressed, the picture starts looking overexposed. Table 3 lists the bright compression of each player (the smaller, the better). The iPod was the only player that did well in this category. The other players are being pushed way too hard to deliver the brightest image possible. This compression affects and hurts only the photos. Videos are not affected because of the way the players have been calibrated by their manufacturers (see "Videos and TV-out").

Picture contrast
The steepness of the grayscale determines the contrast within an image. Too much is just as bad as too little. This is crucial component to picture quality. Table 3 shows the rating for the picture contrast measured for each player (determined from the display gamma in the "Technical information" sidebar). Most of the players deliver too high a picture contrast, which was easy to see in the viewing tests. Under bright ambient light, a boost in picture contrast is often helpful, but that should be a user-controlled option; that way, the pictures also look good in subdued ambient lighting, where picture quality is best appreciated.

Color saturation and gamut
The hues in all color displays are produced through a combination of three primary colors: red, green, and blue. These primaries need to be strong and saturated for the displays to be able to reproduce a wide color gamut. Too little saturation and the pictures look flat and pastel-like; too much saturation and the pictures look gaudy. We measured the primary colors with the Spectroradiometer. The results are in "Technical information" but are summarized in Table 3 by comparing the color gamut of each player to that of a standard high-definition TV or a sRGB computer monitor (the closer to 100 percent, the better). The Creative Zen Vision had a significantly smaller color gamut and saturation than the other players. This was confirmed in the viewing tests.

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