Promoting and Demoting Bit Depth

When you increase bit depth, you introduce no new color information to the original images. Subsequent operators can take advantage of the increased number of possible colors, though.

The following diagram illustrates the color mapping concept.

Just as you can increase (or promote) the bit depth, you can decrease (or demote) it. When bit depth changes, the input colors are mapped (or converted) to the output colors.

A Lookup Table (LUT) describes specific pixel values used in the conversion; all the pixel values are represented by plotting the input and output colors.

LUTs are especially useful for converting between a logarithmic image and a linear image while maintaining color accuracy. For more information, see Using Lookup Tables.