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

Blue hour is the stretch of twilight when the sun is between about 4° and 6° below the horizon — after golden hour has ended in the evening, or before it begins in the morning. The sky glows a deep, saturated blue while there is still enough ambient light to expose a scene, and that balance is what makes it magical: the cool blue of the sky sits in perfect tension with the warm artificial lights of a city, and neither one overpowers the other.

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?

Despite the name, blue hour rarely lasts a full hour. At mid-latitudes it is typically 20–40 minutes. Closer to the equator it is shorter, because the sun plunges almost vertically and races through those two degrees of altitude; at high latitudes it stretches out, and around the summer solstice in far northern or southern locations it can blend into a long, lingering dusk that never fully darkens. The exact figure for tonight depends on where you are, so check the blue hour calculator or your city page for the precise window and plan to be set up before it begins.

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

The two windows are back to back, which is the best-kept secret of light planning. In the evening the sun sets, golden hour fades to warm embers, and blue hour takes over as the sky deepens; in the morning it runs in exact reverse, blue giving way to gold. If you set up for golden hour and simply stay in place, you catch blue hour for free — and it is often the strongest frame of the entire session. To see precisely how the two relate to each other and to the three twilights, read our breakdown of golden hour vs blue hour vs twilight, and if you're new to the warm end of the sequence, start with what golden hour is.