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Posts tagged: Ring Vs Watch

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Macro photograph of finger skin showing the dense capillary network near the surface. The biological reason transmissive PPG works better at the fingertip than the wrist.
SleepPpgForm Factor

Why the Smart Ring Form Factor Is Better for Sleep Than the Wrist: A Physics Argument

The wrist is the worst place to measure heart rate during sleep. It is too thick for transmissive PPG, too prone to motion artifact, and too thermally unstable. The finger wins on every metric that matters for overnight biometrics.

James Hoffmann James Hoffmann
May 29, 2026 13 min read