Autofocus hunts in low light because there is too little contrast or light for the system to lock on. To fix it, give the camera a high contrast target, use a single focus point, add light or an assist beam, use a faster lens and switch to manual focus when the scene defeats the sensor.

How to Troubleshoot Autofocus Hunting in Low Light Conditions

Why Autofocus Hunts

Most autofocus systems measure contrast or compare phase signals from the scene. In dim light, the signal is weak and noisy, so the camera moves back and forth without finding a clear answer. Plain surfaces, such as a dark wall or a clear sky, make it worse. Slow lenses, which admit less light, also give the system less to work with.

Step by Step Fixes

  1. Switch to a single point or a small zone instead of wide area tracking, so the camera does not jump between targets.
  2. Move that point onto a high contrast edge, such as a hairline, a bright sign, the edge of a collar or a light source.
  3. Use single shot focus mode for still subjects, and reserve continuous mode for subjects that move.
  4. Half press the shutter button and let the camera settle before taking the picture.
  5. Open the aperture a little if you are using a slow zoom, as more light improves focus performance.
  6. Lock focus on something at a similar distance, then recompose.

Add Light or Help the Camera

  • Enable the built in focus assist beam if your camera has one and it suits the situation.
  • Use a flash with an assist light, or a small continuous light on the subject.
  • Ask people to face a lamp, window or street light.
  • Check your camera menu for low light autofocus or night modes, as some models include them.

Use Manual Focus as a Backup

When autofocus fails, switch the lens to manual. Turn on focus peaking if your camera offers it, and magnify the view to confirm sharpness. Another technique is to preset the focus distance and then adjust your own position. For wide lenses, a mid range aperture such as f/5.6 to f/8 gives extra depth of field as a first guess, though it needs more light.

Check the Gear

Clean the lens contacts and make sure the lens is fully seated. Test a different lens to see whether the problem follows the lens or the body. Check the maker’s website for firmware updates and notes about focus performance, and contact their support if the issue appears in good light as well.

FAQ

Does a faster lens help?

Generally yes. A wide maximum aperture lets in more light, which often helps the system lock on in dim scenes.

Is back button focus useful here?

It can be. Splitting focus from the shutter button lets you lock focus once and then shoot repeatedly without the camera searching again.

The Short Version

Use one focus point on a contrasty edge, add light or an assist beam, choose a faster lens where possible and switch to manual focus with peaking when autofocus cannot cope.