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<ul class="navigation"><li class="prev"><a accesskey="p" class="prev" href="WS8A20C696-D545-48c3-9851-1B52684555F8.html" title="Making color and tonal adjustments in Camera Raw"><img src="images/blank.gif" alt="Previous" width="17" height="17" /></a></li><li class="next"><a accesskey="n" class="next" href="WSF1B29B95-2419-4b50-A058-A5FE2D7E5E6F.html" title="Preview highlight and shadow clipping in Camera Raw"><img src="images/blank.gif" alt="Next" width="17" height="17" /></a></li></ul><div class="hierarchy" id="hierarchy"><a href="WSB5C0E258-66DE-4089-9CB0-42F396E2B814.html">Camera Raw</a> /
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                <h1>
                    Using histogram and RGB levels in Camera Raw
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                <div><div class="para">A <dfn class="term">histogram</dfn> is a representation of the
number of pixels at each luminance value in an image. A histogram
that has nonzero values for each luminance value indicates an image
that takes advantage of the full tonal scale. A histogram that doesn’t
use the full tonal range corresponds to a dull image that lacks
contrast. A histogram with a spike at the left side indicates shadow
clipping; a histogram with a spike on the right side indicates highlight
clipping. <div class="tip"><img src="images/tip_help.png" />Select Shadows or Highlights to see,
in the preview image, which pixels are being clipped. For more information,
see <a href="WSF1B29B95-2419-4b50-A058-A5FE2D7E5E6F.html">Preview highlight and shadow clipping in Camera Raw</a>.</div></div>
<p>One common task for adjusting an image is to spread out the pixel
values more evenly from left to right on the histogram, instead
of having them bunched up at one end or the other.</p>
<p>A histogram is made up of three layers of color that represent
the red, green, and blue color channels. White appears when all
three channels overlap; yellow, magenta, and cyan appear when two
of the RGB channels overlap (yellow equals the red + green channels,
magenta equals the red + blue channels, and cyan equals the green
+ blue channels).</p>
<p>The
histogram changes automatically as you adjust the settings in the
Camera Raw dialog box. </p>
<p>The RGB values of the pixel under the pointer (in the preview
image) appear below the histogram.</p>
<div class="note"><span class="notetitle">Note:  </span>You can also use the Color Sampler tool&#160; <img src="images/P_ColorSampler_Lg_N.png" /> to
place up to nine color samplers in the preview image. The RGB values
appear above the preview image. To remove a color sampler, Alt-click
(Windows) or Option-click (Mac&#160;OS) it. To clear the color samplers,
click Clear Samplers. </div>
<div class="fignone"><img alt="" id="sca_rgb_values" src="images/sca_rgb_values.png" /><div class="figdesc">The Camera Raw dialog box displays the RGB values of the pixel
under the pointer.</div><br /></div></div>

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