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                <h1>
                    Bit depth
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                <div><p><dfn class="term">Bit
depth</dfn> specifies how much color information is available for
each pixel in an image. The more bits of information per pixel,
the more available colors and more accurate color representation.
For example, an image with a bit depth of 1 has pixels with two
possible values: black and white. An image with a bit depth of 8 has
2<sup>8</sup>, or 256, possible values. Grayscale mode images with
a bit depth of 8 have 256 possible gray values. </p>
<p>RGB images are made of three color channels. An 8‑bit per pixel
RGB image has 256 possible values for each channel which means it
has over 16 million possible color values. RGB images with 8‑bits
per channel (bpc) are sometimes called 24‑bit images (8 bits x 3
channels = 24 bits of data for each pixel). </p>
<p>In addition to 8‑bpc images, Photoshop can also work with images
that contain 16‑bpc or 32‑bpc. Images with 32‑bpc are also known
as high dynamic range (HDR) images. </p>
<div class="section"><h4 class="sectiontitle">Photoshop support for 16‑bit images</h4><div class="para">Photoshop
provides the following support for working with 16-bpc images: <ul><li><p>Working in Grayscale, RGB Color, CMYK Color, Lab Color, and
Multichannel, modes.</p>
</li>
<li><p>All tools in the toolbox, except the Art History Brush tool,
can be used with 16‑bpc images.</p>
</li>
<li><p>All color and tonal adjustment commands, except Variations,
are available</p>
</li>
<li><p>You can work with layers, including adjustment layers, in
16‑bpc images.</p>
</li>
<li><p>Some filters, including Liquify, can be used with 16‑bpc
images.</p>
<p>To take advantage of certain Photoshop&#160;CS4
features, such as some filters, you can convert a 16‑bpc image to
an 8‑bpc image. It’s best if you do a Save As and convert a copy
of the image file so the original file retains the full 16‑bpc image data.</p>
</li>
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