Blue Hour Explained: When It Happens and How to Shoot It

Blue hour describes the blue twilight before sunrise or after sunset. GoldenHourly calculates a narrow planning band with the sun between 4° and 6° below the horizon. In this model it follows golden hour in the evening and precedes it in the morning. Photographers may use the name for a broader period of blue-looking twilight; the visible color and balance with city lights also depend on weather, the scene and exposure.

What causes the blue

Once the sun is below the horizon it no longer lights your surroundings directly. The light you see is sunlight scattered back down from the upper atmosphere, tens of kilometres overhead where the air is still lit. Because short blue wavelengths scatter far more strongly than long red ones, that indirect light arrives heavily weighted toward blue, and because it comes from the whole dome of the sky rather than a single point, it is extraordinarily even and shadowless. There is a brief additional effect near the start of evening blue hour: a band of ozone high in the atmosphere absorbs the remaining red light, which can push the sky toward an even purer, deeper blue than scattering alone would produce.

How long does blue hour last?

Blue hour has no fixed duration. For our −6° to −4° band, the time depends on latitude and date, and it can be much shorter than a full hour. At high latitudes a window may stretch across midnight or fail to occur because the sun does not cross the band. Broader definitions of blue twilight produce different durations, so compare the angle limits before comparing calculators. Choose a location and date in the blue hour calculator, or open your city's light schedule for both morning and evening boundaries.

Best subjects for blue hour

• City skylines. This is the classic blue-hour subject. The exposure balance between the still-blue sky and the lit windows is perfect — neither is blown out nor lost to black.
• Bridges and landmarks with architectural lighting, which switches on right as the sky reaches its richest blue.
• Water reflections, which double the color and the city lights across a still surface.
• Interiors, shop fronts and streets glowing warm against the cool dusk.
• Airports, ports and industrial scenes, where sodium and LED lighting reads vividly against blue.

Camera settings for blue hour

• Use a tripod. Light levels are low and falling, so exposures run from a fraction of a second to many seconds. A tripod is not optional if you want sharp files.
• Keep ISO low (100–400) and let a long shutter do the work. You have time; use it for clean, noise-free images.
• Shoot RAW. The blue is intense and the right white balance is a matter of taste — RAW lets you set it precisely afterward instead of guessing in the moment.
• Bracket your exposures. The dynamic range between a deep sky and bright city lights is wide; bracketing gives you options to blend.
• Start early and keep shooting. The single best few minutes — when sky brightness and artificial light are balanced — come and go quickly, and they arrive at a slightly different moment for every scene.
• Turn on a two-second timer or use a remote release so pressing the shutter doesn't shake a long exposure.

Golden hour and blue hour together

When both windows occur, they meet at the −4° boundary in our model. In the evening golden hour leads into blue hour; in the morning blue hour comes first. For an evening shoot, staying after golden hour lets you photograph the changing balance between sky and artificial lights. For a morning shoot, arrive before golden hour if you want blue hour too. To see how these bands relate to the three twilights, read our breakdown of golden hour vs blue hour vs twilight, or start with what golden hour is.