Lightning: The Branch a Camera Has to Wait For

What looks like a single flash is usually several. A faint stepped leader feels its way down from the cloud in short jumps, and once it connects, a bright return stroke runs back up the same path and heats the air to around 30,000 degrees. Further strokes often reuse that channel within a fraction of a second, which is why lightning sometimes seems to flicker rather than blink.

No one presses the shutter in time for that, so the usual method is to give up on timing. With the camera on a tripod, aperture around f/8 and an exposure of ten to thirty seconds in dim light, the frame simply waits, and whatever strikes inside it gets recorded. Many frames come back empty. Leaving the shutter open also gathers every stroke into one picture, so the main channel can look thicker, or slightly doubled, if wind moved it between strokes.

The thin side branches are the part worth looking for. They are leader paths that never reached the ground, and they fork at loose, uneven angles, nothing like the tidy branching of a tree. Counting seconds until the thunder, roughly three per kilometre, tells you how far off the storm was. On a dark screen the bolt reads as a bright crack across the glass, and the cloud lit from inside fills the rest with a low violet.