What's door B in the camera?

The function of door B is to keep you exposed for a long time. His exposure time is from when you press the shutter to when you release it. It can be exposed for an hour or two. When using B, you must use a tripod, preferably with tools such as cable release.

1。 If your camera can have a 30 "shutter (many small DC's now have a 16" shutter), there is generally no need to use the B door.

2。 Beyond the shutter limit of your camera (camera with B door), you need to use B door, such as exposure 1 minute.

3。 In the case of uncertain exposure time, you can use door B, such as shooting fireworks. Once the fireworks start, let him be exposed, then cover it with a lens cover, and repeat it when the next fireworks come out, so that multiple fireworks can appear in the picture.

4。 If you want to take a night view of the Great Wall, of course, there are no lights on the Great Wall at night. You can open door B, and then find some friends to walk along the Great Wall while flashing lights. Finally, it will be a spectacular night view of the Great Wall. .

5。 Some people mentioned that "you don't have to use door B in case of insufficient light, you can try to increase exposure with a large aperture", but considering that a large aperture will bring about insufficient depth of field, improving iso can improve sensitivity. Of course, you can't improve iso indefinitely, there will be noise.