Color depth or colour depth (see spelling differences), also known as bit depth, is either the number of bits used to indicate the color of a single pixel, in a bitmapped image or video framebuffer, or the number of bits used for each color component of a single pixel.[1][2][3][4] For consumer video standards, such as High Efficiency Video Coding (H.265), the bit depth specifies the number of bits used for each color component.[1][2][3][4] When referring to a pixel, the concept can be defined as bits per pixel (bpp), which specifies the number of bits used. When referring to a color component, the concept can be defined as bits per component, bits per channel, bits per color (all three abbreviated bpc), and also bits per pixel component, bits per color channel or bits per sample (bps).[1][2][5] Color depth is only one aspect of color representation, expressing the precision with which colors can be expressed; the other aspect is how broad a range of colors can be expressed (the gamut). The definition of both color precision and gamut is accomplished with a color encoding specification which assigns a digital code value to a location in a color space.
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Deep color (30/36/48-bit)
Deep color consists of a billion or more colors,[14] 230 is 1.073 billion. Color depths of 30, 36, and 48 bits per pixel are in use, also referred to as 10, 12, or 16 bits per RGB channel/sample/component. Often an alpha channel of the same size is added, resulting in 40, 48, or 64 bits used for each pixel. Some vendors call their 8bit color depth with FRC panels 30-bit panels. A true deep color display has 10bit or more color depth without FRC.
Some earlier systems placed three 10-bit channels in a 32-bit word, with 2 bits unused (or used as a 4-level alpha channel). The Cineon file format that was popular for motion pictures used this. Some SGI systems had 10 (or more) bit D/A converters for the video signal and could be set up to interpret data stored this way for display. BMP files define this as one of its formats, and it is called "HiColor" by Microsoft.
Image editing software such as Photoshop started using 16 bits per channel fairly early. The primary reason this was done was to reduce the quantization on intermediate results (if an operation divided by 4 and then multiplied by 4, it would lose the bottom 2 bits of 8-bit data, but if 16 bits were used it would lose none of the 8-bit data). Digital cameras were able to produce 10 or 12 bits per channel in their raw data, and 16 bits is the smallest addressable unit that was larger than this and would allow raw data to be worked with. These systems did not take advantage of 16 bits for high dynamic range, and some assign almost mystical capabilities to 16 bits that are not actually true.
Video cards with 10 bits per component started coming to market in the late 1990s. An early example was the Radius ThunderPower card for the Macintosh, which included extensions for QuickDraw and Adobe Photoshop plugins to support editing 30-bit images.[15]
The HDMI 1.3 specification defines bit depths of 30 bits (1.073 billion colors), 36 bits (68.71 billion colors), and 48 bits (281.5 trillion colors).[16] In that regard, the Nvidia Quadro graphics cards manufactured after 2006 support 30-bit deep color[17] and Pascal or later Geforce and Titan cards when paired with the Studio Driver[18] as do some models of the Radeon HD 5900 series such as the HD 5970.[19][20] The ATI FireGL V7350 graphics card supports 40-bit and 48-bit color.[21]
The DisplayPort specification also supports color depths greater than 24 bpp in version 1.3 through "VESA Display Stream Compression, which uses a visually lossless low-latency algorithm based on predictive DPCM and YCoCg-R color space and allows increased resolutions and color depths and reduced power consumption."[22]
At WinHEC 2008, Microsoft announced that color depths of 30 bits and 48 bits would be supported in Windows 7, along with the wide color gamut scRGB.[23][24]
High Efficiency Video Coding (HEVC or H.265) defines the Main 10 profile, which allows for 8- or 10-bits per sample with 4:2:0 chroma subsampling.[2][3][4][25][26] The Main 10 profile was added at the October 2012 HEVC meeting based on proposal JCTVC-K0109 which proposed that a 10-bit profile be added to HEVC for consumer applications.[4] The proposal stated that this was to allow for improved video quality and to support the Rec. 2020 color space that will be used by UHDTV.[4] The second version of HEVC has five profiles that allow for a bit depth of 8-bits to 16-bits per sample.[27]
https://en.wikipedia.org/wiki/Color_depth#Deep_color_(30/36/4...
