What does door B exposure mean?

B-gate exposure is a very long exposure.

Door B refers to the shutter mode that opens when the shutter button is pressed and closes when the shutter button is released. Generally used for long exposure of more than ten seconds. This is a function that professionals can only use when shooting in special low light conditions. There are not many digital cameras with B doors. Generally, only a few professional models will be equipped with B doors. A DC without manual exposure control function will definitely not have a B-gate. DC has the function of manual exposure control. When the shutter speed is adjusted, the machine with B door will display a B word. If you can't find B, there will be no B door. Door B is the slowest shutter. You can be as slow as you want, as long as you hold it down, it won't close. Art photography usually uses door B, which can shoot streamlined light. When the light is particularly bad, you can also use door B and press it for a long time to increase the film exposure, but the specific operation depends on your own experience. Try not to use the B-door in general photography, because it is easy to overexpose the film with the B-door. ..