Blue Hour & Twilight Photography Guide

Discover the science of stratosphere ozone absorption and how to photograph serene electric blue cityscapes.

Today's Blue Hour Windows (New York reference)

🌌 Morning Blue Hour
🌃 Evening Blue Hour

Blue Hour Science & Camera Tips

Blue hour sits between civil and nautical twilight, roughly when the Sun is 4 to 8 degrees below the horizon. Unlike golden hour, which is caused by Rayleigh Scattering, blue hour is governed by Chappuis Absorption in the stratosphere: ozone molecules absorb reddish and yellow wavelengths while letting deep blue light pass through, casting a rich indigo glow across the whole sky. City lights, streetlamps, and building illumination switch on right around this time, balancing beautifully against the darkening indigo sky.

Camera Settings for Blue Hour

  • Tripod: Mandatory. Exposure times commonly run 2–15 seconds since the Sun is already below the horizon.
  • Aperture: f/8–f/11 keeps architecture sharp and produces crisp starburst flares around point-source streetlights.
  • ISO: Keep it low (100–400) and rely on your tripod rather than raising ISO, to avoid noise in the shadow-rich sky gradient.
  • Shutter release: Use a remote trigger or 2-second timer to avoid shake from pressing the shutter button during long exposures.

Best Subjects

City skylines, waterfronts, bridges, and illuminated architecture are the classic blue hour subjects, since the contrast between warm artificial light and cool ambient sky creates strong, cinematic color separation. For the full physics explanation and an extended shot list, read our Blue Hour Explained article, or check exact timing for your own city on our city pages.

Blue Hour Frequently Asked Questions

Blue Hour occurs when the Sun is positioned between 4 degrees and 8 degrees below the horizon.
Ozone molecules in the high stratosphere absorb reddish and yellow wavelengths while selectively scattering deep indigo wavelengths (Chappuis Absorption).
Yes, because the sun is below the horizon, shutter speeds range from 2 to 15 seconds. A sturdy tripod is mandatory to prevent blur.
Blue hour typically lasts 15 to 30 minutes, though it can stretch much longer at high latitudes, especially in summer.
They overlap heavily but are not identical terms. Civil twilight is a precise scientific definition (0° to -6°); blue hour is a photography term usually referring to roughly -4° to -8°.