Theoretical knowledge of photographic optics

Shutter 1/25 means that the shutter opening time (exposure time) is 1/25 seconds, and 1/400 means 1/400 seconds.

Compared with F2.6, F2.7 has a larger aperture.

Optical zoom is independent of aperture size.

The larger the aperture, the smaller the depth of field, that is, the more blurred the background.

Depth of field refers to the distance from the nearest point to the farthest point where the camera can clearly image under a certain aperture value.