My camera has a 'bulb mode,' and several questions on photo-SE refer to using Bulb Mode. A few questions:
- What is 'Bulb Mode?'
- Why is it called 'Bulb Mode?'
- What is 'Bulb Mode used for?
The bulb mode is simply a mode where you control the exposure time by holding down the shutter release button.
The name comes from the time when the shutter was controlled by a rubber bulb at the end of a hose. You compressed the bulb to open the shutter, and it would stay open as long as you held the bulb compressed.
Bulb mode is mostly used when you want a longer exposure than the camera settings allow for. Typically you can set the exposure time up to something like half a minute, so for exposures longer than that you have to control it manually.
Typically you would have the camera on a tripod and use a remote shutter release, so that you don't have to push the button on the camera, as that would cause the camera to move. Some remote shutter controls let you lock the button in the pressed state, specifically intended for bulb mode.
Bulb mode is for exposures longer than what the camera will meter for, (5 minutes...) and hand-held shots in low light with a handheld external flash. You can open the shutter, trigger the flash once or more, and close the shutter. It's a great tool for multiple exposures.
1) It is a shutter speed where the photographer taking the picture can control the shutter speed manually. So basically you can have a shutter speed from a couple of fractions of a second to hour. Depends how long you can hold that shutter button. But you could also use a remote release to do this job for you.
2) If i remember right its a very only terminology where an air bubble was to be pressed to open the shutter and release of it would close it.
3) Bulb mode is mainly used for shooting long exposures. For example fireworks, light trails, star trails etc. Also a very popular use is for light painting.