How to use the B door of SLR camera?

Gate B is the slowest shutter speed of digital SLR cameras, usually 30 seconds. If you need more exposure time, you need to shoot in B-door mode. If it is a professional digital SLR camera, door B is an independent exposure mode, which can be found in the exposure mode dial and marked with "B".

Turn it to the selected location. The exposure mode of entry-level SLR camera needs to be changed to M file. When setting the shutter speed, just adjust the shutter speed to the slowest (30 seconds), and then continue to turn the camera wheel to enter the B-door mode, and "light bulb" will be displayed on the shutter speed.

When using the B-door mode, as long as the photographer holds down the shutter button, the shutter of the camera can be opened continuously, allowing unlimited exposure. In some cameras, the B-door mode can set the exposure time range. As long as you press the shutter button, the camera will start timing. When the set time is reached, the camera will automatically close the shutter to complete the exposure shooting.

Some cameras can be set to open the shutter after pressing the shutter key and close the shutter when pressing the shutter key again. The length of exposure time is freely controlled by the photographer, and it does not need too precise timing. Generally, a timer or watch can be used. When shooting in B-door mode with the shutter button of the camera, the photo will become blurred due to the jitter when the shutter is pressed.

Generally, the external cable is released or the shutter is locked by the remote controller to ensure the stability of the camera. Some cable release or remote control can set the time to automatically close the shutter. After setting the external cable release time, press the cable release shutter to leave the camera. Cable release will automatically close the shutter at a predetermined time.

Extended data:

Door b has two main functions:

1, manually control the exposure time.

When in the B door, press the shutter to start exposure, and release the shutter to end exposure, so that the exposure time can be controlled according to different subjects.

For example, when shooting fireworks, the blooming time of fireworks is uncertain. Press the shutter when it rises to a certain height, and release the shutter after flowering.

For example, when shooting lightning, lightning appears irregularly, so press the shutter when lightning appears and release the shutter when lightning disappears.

2. The exposure time can exceed 30 seconds.

The exposure time of manual exposure, shutter priority, aperture priority and other modes can reach 30 seconds.

When you need a long exposure time, such as shooting the starry sky, you should adjust the exposure time to gate B. Theoretically, when the camera is powered off, the exposure time can be adjusted from a few seconds to several hundred minutes. The exposure time can be adjusted from a few seconds to hundreds of minutes, and it can be released when the shutter is pressed.

Door B can freely adjust the exposure time, breaking the 30-second limit. It plays a very powerful role in long exposure photography (slow door).