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I'm trying to figure out how many distinct colors are in p3 color gamut, can't seem to find the answer anywhere.
What I want to figure out is what is the minimum color depth required to fully support p3? Sounds like Apple iMac 5k from 2015 supports p3 but only has an 8 bit display, so I'm wondering how they can support p3 on a 8 bit display panel if the color gamut has billions of color
A Color Gamut refers to colors within a Color Space which is a representation of which colors exist within it and which ones are not.
It does not usually define a representation which is why there is not specific number of colord within it. sRGB for example use 3 chromacities which form a triangle within all possible colors. When one uses an 8-bit-per-component or 24 bits-per-pixel, it has 16,777,216 colors. When one uses 10-bits per color component or 30 bits-per-pixel, it has 1,073,741,824. TIFF files can use 32-bit values per component and so are able to represent even more colors with the sRGB color space.
So, there is no answer to your question but the screen determines how many colors can be displayed. Even so, it does not tell you which ones since the gamma affects spacing between colors and make it non linear. This means that two 8-bit monitors show the same number of colors within a color-space yet they may not show all the same colors. It gets worse if you calibrate your graphics card rather than the display. The LUTs loaded into the graphics card map an 8-bit input from the OS to the input that is supported by the monitor (usually 8 or 10-bits), in the worse case of an 8-bit monitor, after calibration it will not even use all possible colors which is why this often results in banding! It is immensely better to calibrate the monitor which can have 12 or 14-bit Hardware LUTs, so they can map a full 8-bit input to the bit-depth of the display without loss of the number of possible colors shown.
Photo engineers strive to make images that are faithful reproductions of reality. The current state of the art is to fracture an image of a vista via red, green and blue filters. These are the light primary colors. Computer screens, phone screens, and giant movie screens present these three images and our eye/brain combination discerns a color image. The DCI-P3 is a digital color gamut designed to mimic photographic film. This standard is based on a projector equipped with a xenon light source. The idea is to equip the projector with red, green, and blue filters adjusted to reduce “cross talk” that results should the filter be a mismatch to the light source. No computer or phone or TV screen can accurately match such a system but they can come close.
As to the number of color that results, this is a function of bit depth. 8 bit color = 256 shades per each of the three primary colors. 16 bit color delivers 4,096 levels of intensity per each primary color.
While the applied signals are as advertised, I find it doubtful that the actual illumined picture elements respond linearly. In other words, I strongly doubt that any system actually delivers the number of color advertised.
