In computer graphics, color depth or bit depth is the number of bits used to represent the color of a single pixel in a bitmapped image or video frame buffer. This concept is also known as bits per pixel (bpp), particularly when specified along with the number of bits used. Higher color depth gives a broader range of distinct colors.
Color depth is only one aspect of color representation, expressing how finely levels of color can be expressed; the other aspect is how broad a range of colors can be expressed (the gamut).
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components (e.g. RGB and CMYK are color models).
The RGB color model is implemented in different ways, depending on the capabilities of the system used. By far the most common general-used incarnation is the 24-bit implementation, with 8 bits, or 256 discrete levels of color per channel. Any color space based on such a 24-bit RGB model is thus limited to a range of 256x256x256 ≈ 16.7 million colors. Some implementations use 16 bits per component for 48 bits total, resulting in the same gamut with a larger number of distinct colors.
RGB uses additive color mixing, because it describes what kind of light needs to be emitted to produce a given color. Light is added together to create form from out of the darkness. RGB stores individual values for red, green and blue. RGBA is RGB with an additional channel, alpha, to indicate transparency.
Common color spaces based on the RGB model include sRGB, Adobe RGB and ProPhoto RGB.
YUV 4:4:4 closely resembles RGB since in YUV 4:4:4 there is no downsampling of the chroma channels.
See YUV and RGB conversion
YUV is a color space typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently masked by the human perception than using a "direct" RGB-representation. However, YUV 4:2:2 and YUV 4:2:0 subsampling implements less resolution for chroma information than for luma information, resulting in loss of color definition.
TRUDEF™ 24 bit RGB/YUV 4:4:4
Click for larger view
Example of YUV 4:2:0 Color Loss
Click for larger view