Since all medias (sounds, images and video) are now digital, their storing de facto is too. IT is comfortable with these as they are based on a treatment and handling exclusively digital
bit : digital unit
It’s a digital world, its unit : the bit, There is only 2 states : on/off ; black/white; full/empty. And the quantity of bit used for recording,simulate, restore, can be colossal (this is the purpose of the Codecs). Here I will focus on the digital coding of the pixel’s (“PICTure ELement”) color in an image, with various numbers of bit :
- 1 bit : 0 or 1 : black or white : 2 shades
- 2 bits : 00, 01, 10, 11 : Black, Dark Grey, Light Grey, White : 4 shades
- 3 bits : 000, 001, 010, 011, 100, 101, 110, 111 : 8 shades
- 8 bits : 256 shades
- 10 bits : 1024 shades
- 24 bits : 16,7 Millions of shades
- 30 bits : 1,07 Billion of shades
- 36 bits : 68,7 Billions of shades
For the mathletes : the formula is: n bits=2^n ou 2(power)n or 2x2x2x2x2(n times) shades.
For a 24 bits image (16,7 Million color shades), they are fairly distributed between each layer: so 8 bits of the red shades, 8 bits for the green shades and 8 bist for the blue shades.
For a 30 bits image (1,07 Billion color shades), they are fairly distributed between each layer : 10 bits for the luminance shades (Y), 10 bits for the first chrominance shades (U) and 10 bits for the 2nd chrominance shades (V).
The fourth alpha layer (optionnal) has its own number of shades, independently of the 3 first layers.
In a video , the depth of an image is the number of bit of one of the 3 layers
|Color Space||Bits / layer||Bits / Pixel||Shades||Data Type|
|ACES||16-bit||48-bit||328.9 thousand Billion||float|
|Rec. 2020 / P3 DCI||12-bit||36-bit||68.7 Billions||integer|
|Rec. 2020 / Adobe RGB||10-bit||30-bit||1.07 Billion||integer|
|Rec. 709 / sRGB||8-bit||24-bit||16.7 Millions||integer|
We can note dans the more recent the standard is, the more important is the number of shades to stay coherent this a Gamut even bigger.