eli5 what is bit depth in film?
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Your eyes have receptors for three colours: red, green and blue (and they are not very good at separating them, but that’s another issue). So in order to show you any colour, your screen simply has to mix these three colours in any combination to trigger these receptors, and you get to see any colour.
Because of the way computers work, the easy and usually “good enough” way to represent these colours was in three numbers that each take up 8 bits (=1 byte , which is just how most computers organize data internally). With 8 bits you can represent 256 different variations of each shade, and with three of them, that adds up (or rather: multiplies) to some 16 Million different shades of colours. More than enough for most situations, one might say.
However, there are situations where this is a bit too little: think of an evening sky, which gradually changes from one shade of blue to another over a larger area. What can happen here is that there are just not enough colour variations available and you get “bands” of the same colour when you see this on the screen.
One workaround is to “dighter” the colours, i.e. add a bit of noise, so the bands don’t become so apparent, but the better solution is to just double or even quadruple the number of colours by using 9 or even 10 bits per colour instead of 8.
This gives especially photography a lot more “room” in the colour space, and there will be much smoother gradients – or even greater details between very bright and very dark parts of the image, etc. It has the disadvantage that now the pictures need a lot more memory or bandwidth to store or stream.
Today, not all equipment (screens, graphic adapters, etc.) are fully able to handle these higher bandwidths, or to display the images – and honestly, just for watching some clips on YouTube it is normally not really relevant anyways – even less so for typical office work. Where it becomes interesting is either if you are an image artist and you are working on photography – or for watching movies. Well, maybe games look better, too 😉
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