Challenge 3: Levels vs. Curves for Contrast Correction — Solution Walkthrough

The practical difference:

Per this chapter's own material, Levels offers three fixed control
points — black point, white point, and midtone — remapping only those
three specific values across the tonal range. Curves instead lets you
plot an arbitrary curve mapping any input brightness value to any
output brightness value, with as many control points as needed placed
anywhere along that curve, not limited to three fixed positions.

Why Curves offers more precision:

Because Curves isn't restricted to three fixed points, it can address
a very specific, narrow tonal range (brightening only the midtones in
a particular narrow band, for instance) without disturbing the
shadows or highlights the way a broader Levels adjustment covering
the same general area might. This finer control is exactly what makes
it more precise for a correction that needs to target a specific,
narrow tonal problem rather than a broad overall adjustment.

Why a professional retoucher would prefer it for a tricky correction:

A "particularly tricky" correction, by definition, likely involves a
tonal issue that doesn't map cleanly onto Levels' own three fixed
sliders — a very specific band of tones needing adjustment while
leaving everything else completely untouched. Curves' own flexibility
to place control points exactly where needed makes it the natural
choice once Levels' own simpler, coarser control isn't precise enough
to isolate the specific problem.

WHY THIS WORKS AS AN ANSWER
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This exercise checks that the Levels-vs-Curves distinction is
understood as a difference in precision and flexibility — three fixed
points versus an arbitrary mapping — rather than simply "Curves is the
more advanced-sounding tool."