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6 Move the Eyedropper tool over those sections of the image whose grayscale values you want to measure.

Here you're looking for sections of the image that display diffuse white highlights, rather than the bright white you'd need to display and print with detail. Tanua's shirt is an example of a diffuse white highlight.

If you move your cursor over the right side of Tauna's white shirt and measure its grayscale, you'll notice that the grayscale value averages around 26 to 27 percent.

These mid-to-high 20-percent-grayscale values are too high for this diffuse highlight area to appear bright white. (Such high values are one big reason why this image appears flat and dingy.)

7 Choose ImageoAdjustmentso Levels to call up the Levels dialog box (with its accompanying Histogram).

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Photoshop Confidential

Dealing with Two Types of Highlights

^Host discussions of highlights don't mention that there really are two types of highlights: the specular highlight and the diffuse highlight. A specular highlight is one that is pure white — one with a K percentage value of 0 (or an RGB value of 255). A specular highlight contains no detail, and therefore will print with no halftone dot. The diffuse highlight, on the other hand, does contain detail — and those details are precisely what need to be preserved when you set a highlight value. When evaluating highlights in images, always look for diffuse highlights — the lightest portion of an image that still has detail. And if this highlight is supposed to be a white highlight, the Luminance value (whether K or RGB) should be set so that this white highlight "looks" white but still shows detail. For most commercial printers and high-quality desktop printers, a good, safe highlight setting is K=5 percent / RGB=242. If the detail is lost, the highlight will look flat or "blown out," as if the parts of the light exploded into a blur. (You can see this effect in newspapers when highlight values of less than 15 percent fail to print.) This results in a pure white area (sometimes referred to as a blown-out area) with no image detail present.

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