Some small problems about aperture size and depth of field ~ ~

Small aperture and large depth of field. If you want to get enough light, extend the exposure time-that is, we often say slow shutter.

You can understand it as receiving water with a cup under the tap. A large aperture is like a faucet with a large output, and it takes a relatively short time to fill the cup. A small aperture is like a faucet with a small water output. It takes longer to fill the cup.

The second question.

Maybe you have a misunderstanding about constant aperture. For example: 24-70F2.8 It means that the maximum aperture of the lens is F2.8 regardless of the focal length of 24 or 70. How about 24-70F2.8-F4? This means that the maximum aperture at the 24-end is F2.8, while the maximum aperture at the 70-end is F4. Then the former is F2.8 constant aperture and the latter is not. So a lens with a constant aperture can also be shot with a small aperture.

The third question.

Large aperture and depth of field. First of all, controlling the depth of field is closely related to the focal length besides the aperture size. For example, the depth of field of 70mm focal segment is smaller than that of 24mm under the same aperture of F3.5, so it needs a large aperture and a large depth of field, so it needs to be shot with a wide-angle end.