> If we're happy to skip 1.5 times brighter, why can't we skip all the even integer times brighter values, and use 19 bits?

Things get wonky if you don't have a linear scale with a true zero; in such a scale the low end of your N:1 contrast ratio (in the smallest representation) has a value of 1, and the high end has a value of N.

Good thing in real life there's no such thing as truly zero photons, then (which is a detail the article actually shortly touches upon).

Also, if that type of "wonky" throws off your rendering pipeline, you're bound to get something else wrong.

Such as ever having a linear scale with a small number of bits in your pipeline. The linear scaled brightness stays afloat all the way through (cause floats have this handy feature of being transparently sorta-logarithmic in the way they use their bits, even 16-bit floats beat 20-bit ints for that purpose), only at the very end you apply the tonemap+gamma function(s), then dither, then truncate to fixed (8) bit integer.

Hmm… but the actual display’s representation of 0 cannot be darker than the minimum brightness value it supports. If 1 really is 1x the minimum, then 0 and 1 have to be displayed identically. But then your scale isn’t even linear, nor does it have a true zero. How does that help?

edit: And aren’t output color spaces already highly nonlinear due to gamma correction?

0 is the lowest and x-1 is the highest for a ratio of 1:x. It’s 1 all the way to x; You just subtract one because computers start counting from 0

But in that case, skipping "even integer times brighter values" wouldn't exclude 0 - because 0 is 1x brighter, an odd integer.

Is that the reason you can’t just chop off the two least significant bits when converting from 10-bit to 8-bit?