It's a problem of presenting that contrast ratio on a screen that is not capable of a contrast ratio of 1,000,000:1 If you have such a high contrast ratio,

It's a problem of presenting that contrast ratio on a screen that is not capable of a contrast ratio of 1,000,000:1 If you have such a high contrast ratio, it also means you have discretized amount of light in such amount or more. Talking about the number of bits minimum needed indeed makes the assumption you are storing and manipulating light in a linear way (hypothesis not true for most 8 bpc rgb values).