How to use the door B of SLR?

The slowest shutter speed of a digital SLR camera is generally 3 seconds. If you need to take a longer exposure, you need to use B-door mode to shoot. 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 the word "B".

just turn it to the selected position. For the B-door exposure mode of an entry-level SLR camera, you need to turn the exposure mode to M-block. When setting the shutter speed, just adjust the shutter speed to the slowest (3 seconds), and then continue to turn the camera wheel to enter the B-door mode, and the shutter speed will display "Bulb".

when using the b-door mode, as long as the photographer holds down the shutter button, the shutter of the camera can continue to open, allowing the exposure to continue indefinitely. The B-door mode of some cameras can be exposed within a set time range. As long as the shutter button is pressed, the camera starts to time, and after the set time, the camera automatically closes 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 there is no accurate timing. Generally, it is timed by a timer or watch. When shooting in B-door mode with the shutter button of the camera, the photo will be blurred because of the jitter when the shutter is pressed.

generally, an external cable release or shutter remote controller is used to lock the shutter for shooting, so as to ensure the stability of the camera. Some cable release or shutter remote controllers can set the time to automatically close the shutter. After setting the time on the external shutter line, press cable release's shutter to leave the camera. When the time is set, cable release will automatically close the shutter.

Extended information:

Gate B has two main functions:

1. Manually control the exposure time.

When at Gate B, 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 the blooming.

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

2. The exposure time can exceed 3 seconds.

the exposure time of manual exposure, shutter priority, aperture priority and other modes is at most 3 seconds.

when you need a longer exposure time, such as shooting the starry sky, you need to adjust to the B gate. Theoretically, the exposure time can be adjusted from a few seconds to hundreds of minutes until the camera runs out of power. Press the shutter and then release it when the time is almost the same.

door b can freely adjust the exposure time, breaking through the limitation of 3 seconds. It plays a very powerful role in long exposure photography (slow door).