@duerer that is because you are a human and used to start counting at 1 (and right you are!)…
There are, however 256 different ‘combinations’ possible from 0 to 255, which gives us (‘naturally’) natural numbers 1 to 256 and half of 256 is 128 and not 127.5 😉
(You could of course also map 256 shades of grey to 8 bits…)
The decision to start counting at zero might seem a bit strange, but it comes from the fact that 0000 0000 (for instance) is being ‘mapped’ to 0….(even when describing negative numbers or fractions…).
