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            <div class="Photoshop"><table><tr><td class="banner">Adobe Photoshop CS4</td><td class="pod"><img src="images/PDF.gif" width="16" height="16" hspace="15" valign="50%" />&#160;&#160;
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<ul class="navigation"><li class="prev"><a accesskey="p" class="prev" href="WS6EC2A68B-AE8D-4987-87E2-28272B744445a.html" title="Channels"><img src="images/blank.gif" alt="Previous" width="17" height="17" /></a></li><li class="next"><a accesskey="n" class="next" href="WS7E170648-AE6A-43fd-89FB-2F11FA7B1684a.html" title="Channels panel overview"><img src="images/blank.gif" alt="Next" width="17" height="17" /></a></li></ul><div class="hierarchy" id="hierarchy"><a href="WSfd1234e1c4b69f30ea53e41001031ab64-7701a.html">Selecting and masking</a> /
     <a href="WS6EC2A68B-AE8D-4987-87E2-28272B744445a.html"><b>Channels</b></a> 
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                <h1>
                    About channels
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                <div><p><dfn class="term">Channels</dfn> are grayscale images that store
different types of information:</p>
<ul><li><p><dfn class="term">Color information channels</dfn> are created automatically
when you open a new image. The image’s color mode determines the
number of color channels created. For example, an RGB image has
a channel for each color (red, green, and blue) plus a composite
channel used for editing the image.</p>
</li>
<li><p><dfn class="term">Alpha
channels</dfn> store selections as grayscale images. You can add
alpha channels to create and store masks, which let you manipulate
or protect parts of an image.</p>
</li>
<li><p><dfn class="term">Spot color channels</dfn> specify additional plates
for printing with spot color inks.</p>
<p>An
image can have up to 56 channels. All new channels have the same
dimensions and number of pixels as the original image.</p>
<p>The
file size required for a channel depends on the pixel information
in the channel. Certain file formats, including TIFF and Photoshop
formats, compress channel information and can save space. The size
of an uncompressed file, including alpha channels and layers, appears
as the rightmost value in the status bar at the bottom of the window
when you choose Document Sizes from the pop‑up menu.</p>
<div class="note"><span class="notetitle">Note:  </span>As long as you
save a file in a format supporting the image’s color mode, the color
channels are preserved. Alpha channels are preserved only when you
save a file in Photoshop, PDF, TIFF, PSB, or raw formats. DCS 2.0
format preserves only spot channels. Saving in other formats may
cause channel information to be discarded.</div>
</li>
</ul>
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                    <div class="separator">&#160;</div>
                    <div><p><a href="WSfd1234e1c4b69f30ea53e41001031ab64-76c2a.html">About masks and alpha channels</a></p>
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                    <p><a href="http://help.adobe.com/en_US/Photoshop/11.0/WSBFDB3D2F-A3E8-447f-A49A-787D27798562a.html" title="http://help.adobe.com/en_US/Photoshop/11.0/WSBFDB3D2F-A3E8-447f-A49A-787D27798562a.html">About spot colors (adobe.com)</a></p>
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