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Only 3 bits are used for the red channel in the left two images, 8 bits in the right image. 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.
For each unique palette, an image color test chart and sample image (truecolor original follows) rendered with that palette (without dithering) are given. The test chart shows the full 256 levels of the red, green, and blue (RGB) primary colors and cyan, magenta, and yellow complementary colors, along with a full 256-level grayscale.
For artistic effect, most image editing programs provide a posterization feature, or photographic processes may be used. Unwanted posterization, also known as banding, may occur when the color depth, sometimes called bit depth, is insufficient to accurately sample a continuous gradation of color tone. As a result, a continuous gradient appears ...
Color depth, also known as bit depth, is either the number of bits used to indicate the color of a single pixel, or the number of bits used for each color component of a single pixel. When referring to a pixel, the concept can be defined as bits per pixel (bpp).
where , , and are the color balanced red, green, and blue components of a pixel in the image; ′, ′, and ′ are the red, green, and blue components of the image before color balancing, and ′, ′, and ′ are the red, green, and blue components of a pixel which is believed to be a white surface in the image before color balancing.
A color mapping may be referred to as the algorithm that results in the mapping function or the algorithm that transforms the image colors. The image modification process is sometimes called color transfer or, when grayscale images are involved, brightness transfer function (BTF) ; it may also be called photometric camera calibration or ...
Shaded or gradient areas may produce color banding which may be distracting. The application of dithering can help to minimize such visual artifacts and usually results in a better representation of the original (Figure 3). Dithering helps to reduce color banding and flatness.
Test cards typically contain a set of patterns to enable television cameras and receivers to be adjusted to show the picture correctly (see SMPTE color bars).Most modern test cards include a set of calibrated color bars which will produce a characteristic pattern of "dot landings" on a vectorscope, allowing chroma and tint to be precisely adjusted between generations of videotape or network feeds.