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<ul class="navigation"><li class="prev"><a accesskey="p" class="prev" href="WSfd1234e1c4b69f30ea53e41001031ab64-768ca.html" title="About histograms"><img src="images/blank.gif" alt="Previous" width="17" height="17" /></a></li><li class="next"><a accesskey="n" class="next" href="WSfd1234e1c4b69f30ea53e41001031ab64-7686a.html" title="View the histogram for a multilayered document"><img src="images/blank.gif" alt="Next" width="17" height="17" /></a></li></ul><div class="hierarchy" id="hierarchy"><a href="WSfd1234e1c4b69f30ea53e41001031ab64-7693a.html">Color and tonal adjustments</a> /
     <a href="WSfd1234e1c4b69f30ea53e41001031ab64-768da.html"><b>Viewing histograms and pixel values</b></a> 
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                <h1>
                    Histogram panel overview
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                <br clear="both" /><div id="minitoc"><div class="t"><div class="b"><div class="l"><div class="r"><div class="bl"><div class="br"><div class="tl"><div class="tr"><div><h3>Contents [<a href="#" onclick="return toggleMiniToc('minitoc-links', this);" class="hideLink">Hide</a>]</h3><ul id="minitoc-links"><li><p><a href="#WSfd1234e1c4b69f30ea53e41001031ab64-768aa"><h1 class="topictitle1">Adjust the view of the Histogram panel</h1>
</a></p></li><li><p><a href="#WSfd1234e1c4b69f30ea53e41001031ab64-7689a"><h1 class="topictitle1">View a specific channel in the histogram</h1>
</a></p></li><li><p><a href="#WSfd1234e1c4b69f30ea53e41001031ab64-7688a"><h1 class="topictitle1">View channel histograms in color</h1>
</a></p></li><li><p><a href="#WSfd1234e1c4b69f30ea53e41001031ab64-7687a"><h1 class="topictitle1">View histogram statistics</h1>
</a></p></li></ul></div></div><br clear="both" /></div></div></div></div></div></div></div></div><br clear="both" /><div><div class="p"><span><img src="images/dingbat.png" />&#160;Choose
Window&#160;&gt; Histogram or click the Histogram tab to open
the Histogram panel. By default, the Histogram panel opens in Compact
View with no controls or statistics, but you can adjust the view.</span> <div class="fignone"><img alt="" id="ct_02" src="images/ct_02.png" /><div class="figdesc">Histogram panel </div><br /><dl><dt class="dlterm">A.</dt>
<dd>Channel menu</dd><p class="dlseparator"></p><dt class="dlterm">B.</dt>
<dd>panel
menu</dd><p class="dlseparator"></p><dt class="dlterm">C.</dt>
<dd>Uncached Refresh button</dd><p class="dlseparator"></p><dt class="dlterm">D.</dt>
<dd>Cached
Data Warning icon</dd><p class="dlseparator"></p><dt class="dlterm">E.</dt>
<dd>Statistics</dd><p class="dlseparator"></p></dl>
</div></div>
</div>
<div id="WSfd1234e1c4b69f30ea53e41001031ab64-768aa" class="nochunk"><a name="WSfd1234e1c4b69f30ea53e41001031ab64-768aa"></a><h3 class="topictitle3">Adjust the view of the Histogram panel</h3><div><div class="p"><span><img src="images/dingbat.png" />&#160;Choose a view from
the Histogram panel menu.</span> <dl><dt class="dlterm">Expanded View</dt>
<dd>Displays the histogram with statistics. It also displays:
controls for choosing the channel represented by the histogram,
viewing options in the Histogram panel, refreshing the histogram
to display uncached data, and choosing a specific layer in a multilayered
document.</dd><p class="dlseparator"></p><dt class="dlterm">Compact View</dt>
<dd>Displays a histogram with no controls or statistics.
The histogram represents the entire image.</dd><p class="dlseparator"></p><dt class="dlterm">All Channels View</dt>
<dd>Displays individual histograms of the channels in addition
to all the options of the Expanded View. The individual histograms
do not include alpha channels, spot channels, or masks.<div class="fignone"><img alt="" id="ct_03" src="images/ct_03.png" /><div class="figdesc">Histogram panel with all channels displayed and statistics
hidden</div><br /></div></dd><p class="dlseparator"></p></dl>
</div>
</div></div>
<div id="WSfd1234e1c4b69f30ea53e41001031ab64-7689a" class="nochunk"><a name="WSfd1234e1c4b69f30ea53e41001031ab64-7689a"></a><h3 class="topictitle3">View a specific channel in the histogram</h3><div><div class="section"><p>If you chose the Expanded
View or All Channels View of the Histogram panel, you can choose
a setting from the Channel menu. Photoshop remembers the channel
setting if you switch from either Expanded View or All Channels
View back to Compact View.</p>
</div>
<ul><li class="stepexpand"><span>Choose an individual channel to display
a histogram of the channel, including color channels, alpha channels,
and spot channels.</span></li>
<li class="stepexpand"><span>Depending on the color mode of the image, choose RGB,
CMYK, or Composite to view a composite histogram of all the channels. </span></li>
<li class="stepexpand"><span>If the image is RGB or CMYK, choose Luminosity to display
a histogram representing the luminance or intensity values of the
composite channel.</span></li>
<li class="stepexpand"><span>If the image is RGB or CMYK, choose Colors to display
a composite histogram of the individual color channels in color.
This option is the default view for RGB and CMYK images when you
first choose Expanded View or All Channels View.</span> <p>In the All Channels View, choosing from the Channels menu
affects only the topmost histogram in the panel.</p>
</li>
</ul>
</div></div>
<div id="WSfd1234e1c4b69f30ea53e41001031ab64-7688a" class="nochunk"><a name="WSfd1234e1c4b69f30ea53e41001031ab64-7688a"></a><h3 class="topictitle3">View channel histograms in color</h3><div><div class="p"><span><img src="images/dingbat.png" />&#160;From the Histogram panel, do one
of the following:</span><ul><li><p>In the All Channels View, choose Show Channels
In Color from the panel menu. </p>
</li>
<li><p>In Expanded View or All Channels View, choose an
individual channel from the Channel menu and choose Show Channels
In Color from the panel menu. If you switch to Compact View, the
channel continues to be shown in color.</p>
</li>
<li><p>In Expanded View or All Channels View, choose Colors
from the Channel menu to show a composite histogram of the channels
in color. If you switch to Compact View, the composite histogram
continues to be shown in color.</p>
</li>
</ul>
</div>
</div></div>
<div id="WSfd1234e1c4b69f30ea53e41001031ab64-7687a" class="nochunk"><a name="WSfd1234e1c4b69f30ea53e41001031ab64-7687a"></a><h3 class="topictitle3">View histogram statistics</h3><div><div class="section"><p>By
default, the Histogram panel displays statistics in the Expanded
View and All Channels View. </p>
</div>
<ol><li class="stepexpand"><span>Choose Show Statistics from the Histogram panel
menu. </span></li>
<li class="stepexpand"><span>Do one of the following:</span><ul><li><p>To view information about a specific pixel
value, place the pointer in the histogram. </p>
</li>
<li><p>To view information about a range of values, drag
in the histogram to highlight the range.</p>
</li>
</ul>
 <p>The panel displays the following statistical information
below the histogram:</p>
 <dl><dt class="dlterm">Mean</dt>
<dd>Represents
the average intensity value. </dd><p class="dlseparator"></p><dt class="dlterm">Std Dev (Standard deviation)</dt>
<dd>Represents how widely
intensity values vary.</dd><p class="dlseparator"></p><dt class="dlterm">Median</dt>
<dd>Shows the middle value in the range
of intensity values. </dd><p class="dlseparator"></p><dt class="dlterm">Pixels</dt>
<dd>Represents the total number of pixels used to calculate
the histogram.</dd><p class="dlseparator"></p><dt class="dlterm">Level</dt>
<dd>Displays the intensity level of the area underneath the
pointer. </dd><p class="dlseparator"></p><dt class="dlterm">Count</dt>
<dd>Shows the total number of pixels corresponding to the
intensity level underneath the pointer.</dd><p class="dlseparator"></p><dt class="dlterm">Percentile</dt>
<dd>Displays the cumulative number of pixels at or below
the level underneath the pointer. This value is expressed as a percentage
of all the pixels in the image, from 0% at the far left to 100%
at the far right.</dd><p class="dlseparator"></p><dt class="dlterm">Cache Level</dt>
<dd>Shows
the current image cache used to create the histogram. When the cache
level is higher than 1, the histogram is displayed faster. In this case,
the histogram is derived from a representative sampling of pixels
in the image (based on the magnification). The original image is
cache level 1. At each level above level 1, four adjacent pixels
are averaged to arrive at a single pixel value. So, each level is
half the dimensions (has 1/4 the number of pixels) of the lower
level. When Photoshop makes a quick approximation, it can use one
of the upper levels. Click the Uncached Refresh button to redraw
the histogram using the actual image layer.</dd><p class="dlseparator"></p></dl>
</li>
</ol>
</div></div>

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