Final answer:
The bulb setting on a digital camera is used for long exposures by holding the shutter button open as long as needed, which is useful in low-light conditions or for effects like light trails.
Step-by-step explanation:
When a digital camera allows you to hold the shutter button open for an indefinite amount of time, the setting is known as the bulb setting. The bulb setting is used especially in low light conditions or for long-exposure photography, where the shutter needs to be open for a longer period to allow more light to reach the sensor. This setting is beneficial for capturing things like night skies or light trails.
In auto mode, the camera decides the optimal shutter speed and aperture for you, which is great for quick shots without much preparation. However, if you need to manually control the amount of light or the effect on moving objects in your photographs, you might use semi-manual modes like Shutter Priority or Aperture Priority. In these modes, you can select either the shutter speed or aperture value, and your digital camera will attempt to adjust the other setting accordingly to achieve proper exposure.