Light at Blue Hour

Most people put the camera away when the sun goes. I've spent a lot of evenings learning not to.

What is actually happening

After sunset the sky doesn't go dark all at once. For a while it keeps a deep, even blue, with no hard shadows and no single light source. Photographers call it blue hour, and the common rule of thumb is that the sun sits somewhere between four and eight degrees below the horizon. In practice you can feel it: the day has ended, but the sky hasn't agreed to yet.

It is not an hour. Where I work, in autumn, it's closer to half of one, and the best of it is perhaps ten minutes.

Why it flatters

Daylight argues with you. It makes contrast, it throws shadows across faces, it picks favourites. Blue hour does none of that. The light is soft and comes from everywhere, so a wall, a face and a wet road all hold detail together.

It also does something odd to colour. Anything warm, like a lit window or a shop sign, sits against that blue like a coal in ash. You don't need to compose cleverly. You need to find the one amber thing and put it where the eye will land.

Working in it

I keep the routine short, because the light won't wait.

1. Arrive early and decide the frame in daylight. You won't have time later.

2. Put the camera on something solid. Exposures stretch to a second or more.

3. Expose for the sky, not the lights. Let the windows burn a little.

4. Shoot the same frame every two minutes. The picture changes faster than your eyes can tell.

Streetlights are the complication. They come on partway through, and they come on orange. Some evenings I like the mix and some evenings it looks like a fault. I decide on the spot and don't revisit it.

The ten-minute rule

I tell myself I only have ten good minutes, and I plan for ten. It stops me chasing. On the harbour wall last week I made eleven frames in that window and only one of them is any good, a lit window in a dark house with a boat's mast crossing the sky.

One out of eleven is a fine evening.

A last practical thing, because nobody warned me. The cold is real at that hour. The sun has just taken the day's warmth with it and the air drops quickly, so your hands stiffen right when you need them to be steady. I carry thin gloves with the fingertips cut off and a flask I forget to drink from. The people who make the best pictures at blue hour are mostly the ones who stayed warm enough to stay.

Bring gloves.