Bulb (photography)

In photography, "Bulb" mode (often abbreviated as "B") is a camera setting that allows the photographer to keep the camera's shutter open for an extended, manually controlled duration. Unlike automatic modes or pre-set shutter speeds, Bulb mode requires the photographer to physically hold down the shutter release button (or use a remote shutter release) for as long as they want the shutter to remain open. Once the button is released, the shutter closes.

This manual control offers precise control over exposure time, making it ideal for situations requiring very long exposures. It is particularly useful in low-light environments where capturing sufficient light necessitates exposures longer than the typical maximum shutter speed offered by the camera's programmed modes (usually 30 seconds).

Common applications of Bulb mode include:

• Night photography: Capturing star trails, the Milky Way, or cityscapes at night often requires exposures lasting several minutes or even hours.
• Light painting: Creating artistic effects by moving a light source during a long exposure.
• Fireworks photography: Capturing the trails and bursts of fireworks.
• Lightning photography: Attempting to capture a lightning strike.

When using Bulb mode, it is essential to use a tripod to avoid camera shake and maintain image sharpness. A remote shutter release is also highly recommended to prevent camera movement caused by pressing the shutter button directly on the camera body. The photographer is responsible for accurately timing and controlling the exposure, based on the scene's lighting conditions and the desired effect. Consideration for noise (grain) can also be important with very long exposures.