Challenge 3: Why 8-Bit Shows More Banding Than 16-Bit — Solution Walkthrough

Why 8-bit is more prone to banding:

Per this chapter's own material, bit depth describes how many distinct
tonal values each color channel can represent — 8-bit per channel
offers far fewer discrete tonal steps than 16-bit per channel. Heavy
color grading stretches and remaps tonal values significantly; with
only 8-bit's own limited number of available tonal steps to redistribute
across that stretched range, adjacent pixels that should show a smooth
gradient can end up landing on the same limited set of available
values, creating visible abrupt steps — banding — rather than a smooth
transition.

Why 16-bit handles the same edits better:

16-bit per channel offers dramatically more available tonal values to
begin with, so even after the same aggressive stretching and
remapping, there are still enough distinct values available to
represent a smooth gradient without visibly abrupt jumps between
adjacent tones.

Why this specifically matters for heavy edits rather than any edit:

Per this chapter's own framing, this issue shows up specifically
during extensive editing or color grading — a small, gentle adjustment
in 8-bit is unlikely to exhaust its own limited tonal range in any
visible way, but multiple aggressive adjustments stacked together are
exactly the situation where 8-bit's own limited precision runs out and
banding becomes visible, while 16-bit's own extra headroom tolerates
the same aggressive adjustments far better.

WHY THIS WORKS AS AN ANSWER
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This exercise checks that bit depth is understood as a measure of
available tonal precision, and that banding is explained as a direct
consequence of running out of that precision under heavy editing, not
just a vague "16-bit is better" statement.