Colour banding

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Colour banding

Colour banding is a subtle form of <a href="/en/Posterization" title="Posterization" class="wl">posterization</a> in digital images, caused by the colour of each pixel being rounded to the nearest of the digital colour levels. While posterization is often done for artistic effect, colour banding is an undesired artifact. In 24-bit colour modes, 8 bits per channel is usually considered sufficient to render images in <a href="/en/Rec._709" title="Rec. 709" class="wl">Rec. 709</a> or <a href="/en/SRGB" title="SRGB" class="wl">sRGB</a>. However the eye can see the difference between the colour levels, especially when there is a sharp border between two large areas of adjacent color levels. This will happen with gradual <a href="/en/Gradient" title="Gradient" class="wl">gradients</a> (like sunsets, dawns or clear blue skies), and also when blurring an image a large amount.

<div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none" about="#mwt1">Inaccuracy in computer graphics</div>
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<figure class="mw-halign-right wiki-thumb"><a href="/en/File:The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg" class="mw-file-description image media-thumb" data-hash="File:The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg"><img loading="lazy" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg/418px-The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg" decoding="async" data-file-width="640" data-file-height="371" data-file-type="bitmap" height="242" width="418" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg/627px-The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/b/be/The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg 2x" alt="The_Foston_by_pass_on_the_A1_North_-_geograph.org.uk_-_1068397.jpg"></a><figcaption>An example of colour banding, visible in the sky in this photograph</figcaption></figure>
<figure class="mw-halign-right wiki-thumb"><a href="/en/File:Colour_banding_example01.png" class="mw-file-description image media-thumb" data-hash="File:Colour_banding_example01.png"><img loading="lazy" src="//upload.wikimedia.org/wikipedia/commons/9/9a/Colour_banding_example01.png" decoding="async" data-file-width="418" data-file-height="303" data-file-type="bitmap" height="303" width="418" alt="Colour_banding_example01.png"></a><figcaption>An illustration of colour banding. Only 3 bits are used for the red channel in the left two images, 8 bits in the right image.</figcaption></figure>

Colour banding is more noticeable with fewer <a href="/en/Bits_per_pixel" title="Bits per pixel" class="mw-redirect wl">bits per pixel</a> (BPP) at 16–256 colours (4–8&nbsp;BPP), where there are fewer shades with a larger difference between them.

Possible solutions include the introduction of <a href="/en/Dither#Digital_photography_and_image_processing" title="Dither" class="wl">dithering</a> and increasing the number of bits per colour channel.

Because the banding comes from limitations in the presentation of the image, <a href="/en/Gaussian_blur" title="Gaussian blur" class="wl">blurring</a> the image does not fix this.

Colour banding is a subtle form of posterization in digital images, caused by the colour of each pixel being rounded to the nearest of the digital colour levels. While posterization is often done for artistic effect, colour banding is an undesired artifact. In 24-bit colour modes, 8 bits per channel is usually considered sufficient to render images in Rec. 709 or sRGB. However the eye can see the difference between the colour levels, especially when there is a sharp border between two large areas of adjacent color levels. This will happen with gradual gradients , and also when blurring an image a large amount. Colour banding is more noticeable with fewer bits per pixel at 16–256 colours , where there are fewer shades with a larger difference between them. Possible solutions include the introduction of dithering and increasing the number of bits per colour channel. 