Challenge 3: Aggressive Sharpening on a Genuinely Out-of-Focus Photo — Solution Walkthrough

Why this happened:

Per this chapter's own warning box, Unsharp Mask only boosts contrast
at edges that already exist in the image's own data — it cannot
invent detail that was never actually captured by the camera in the
first place. A photo that was genuinely out of focus when taken has
little to no real edge information for Unsharp Mask to detect and
amplify, since the actual optical blur at capture time destroyed that
edge detail before the image was ever saved.

Why the result came out harsh and noisy instead of sharp:

With no real edges to boost, aggressive Unsharp Mask settings instead
amplify whatever subtle contrast variations do exist — much of which,
in an out-of-focus photo, is simply sensor noise rather than genuine
detail. Boosting that noise heavily produces the harsh, artificial-
looking result described, rather than anything resembling genuine
sharpness, since there was no real edge information available to
recover.

The correct expectation to have going in:

Per this chapter's own material, sharpening is a tool for enhancing
existing, already-present detail — not a way to reverse actual optical
blur captured at the moment a photo was taken. A genuinely out-of-
focus photo has a fundamental data problem sharpening cannot solve, no
matter how aggressively it's applied.

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise directly applies this chapter's own warning box to the
exact failure mode it describes, correctly explaining the mechanism
(no real edges to boost, so noise gets amplified instead) rather than
just restating that sharpening "doesn't work" on blurry photos.