NHT · Night & Astro
Long Exposure Night Photography: 10 Seconds to 10 Minutes
How to meter, expose and control noise when a single frame lasts longer than any light meter can handle.
Diagrams
Long exposure night work starts with four pieces of kit: a solid tripod, a remote release, manual mode, and Bulb mode for exposures beyond 30 seconds. Your camera's meter becomes unreliable in the dark, so you reason in stops instead. Take a starting point of f/2.8, ISO 3200 and 10 seconds, look at the frame, and adjust. Once you like the brightness, you can trade ISO down for time: dropping from ISO 3200 to ISO 800 costs two stops and so doubles the shutter twice, giving 40 seconds with the same exposure. That is how you reach a clean 5-minute file without guessing.
Noise is the main enemy of long exposures, and it has two sources. Random noise is reduced by a low ISO; heat noise, which appears as bright coloured dots, grows the longer the sensor stays powered and the warmer the night. In-camera long exposure noise reduction takes a second, dark frame of the same length and subtracts it, which works well but doubles your waiting time — on a 5-minute exposure that means 10 minutes per shot. For sequences, such as star trails, disable it and shoot separate dark frames to subtract later, or photograph on a cold night, which is genuinely the cheapest noise reduction available.
What you shoot with the technique matters as much as the technique. Long exposures turn moving water into glass, cloud into streaks, traffic into rivers of light, and stars into arcs. Each subject has a natural exposure: 2 to 8 seconds for a silky waterfall, 10 to 30 seconds for car trails, 30 seconds to a few minutes for streaking clouds, and 20 minutes or more for star trails. Match the length to the effect you want rather than always reaching for the maximum.
A few practical habits save whole shoots. Use the viewfinder cover or a piece of tape over the eyepiece, because stray light leaks in during multi-minute frames. Start with a fully charged battery and carry a spare, since long exposures drain cells quickly. Never touch or nudge the tripod during the exposure, and hang your bag from the centre hook rather than resting a hand on the camera. Finally, review the raw file at 100% for hot pixels and light leaks before you pack up and leave the location.
Key points
- Meter by reasoning in stops: start at f/2.8, ISO 3200, 10 seconds, then halve the ISO and double the time to reach a clean long exposure.
- Long exposure noise reduction doubles your waiting time by shooting a dark frame, so disable it for stacking sequences and subtract dark frames later.
- Match exposure length to the subject: 2-8 seconds for water, 10-30 seconds for car trails, 20 minutes or more for star trails.
- Cover the viewfinder, carry a spare battery, and check the RAW file at 100% for hot pixels and light leaks before leaving.
