The longest automatic shutter speed setting on digital cameras is 30 seconds, which is fine for most subjects. However, there are some situations when you need to make much longer exposures – after dark, for example. This is where your camera’s Bulb mode – (B) exposure setting – comes in. This handy setting allows you to hold the shutter open for as long as required, enabling exposures of minutes (or hours) to be made.
It’s best to use Bulb mode when shooting star trails, night scenes illuminated by the moon, vehicle light trails, firework displays, lightning and when using long exposures created by a strong Neutral Density filter.
It’s very effective for recording a succession of fireworks over a period of time on a single image. You can shield the front of the lens with your hand or a piece of card between fireworks to stop light reaching the sensor.
Bulb mode is accessed on most cameras either by a designated exposure mode setting often displayed as ‘B’ on the top dial or via Manual exposure mode – by scrolling one click below 30 seconds until BULB appears in the display.
In Bulb mode, the shutter will remain open for as long as the shutter-release button is depressed, allowing you to make exposures of any length of time. It’s possible to do this with your finger, but it’s not very practical. Instead, you can use a remote shutter release to open and close the shutter.
How to set up and use Bulb mode
01 Avoid camera shake
Use a tripod or solid support to ensure there is no camera movement during a long exposure. Make sure the tripod is secure and won’t be subject to any vibrations from the wind, keeping it low if necessary. Turn off any anti-shake features on the lens and camera.
02 Use a remote release
A remote shutter release with a lock facility allows you to keep the shutter open for as long as necessary. The shutter is then closed by releasing the lock, which ends the exposure. Some remotes have an integrated timer to set the exposure length.
03 Expose manually
Bulb is a manual mode, so you need to determine aperture and exposure settings before you shoot. Set an aperture of f/8 and experiment with exposure times. If your shot is too dark, extend the time; if it’s too light, shorten it. Use a low ISO to eliminate noise.
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