I still don't understand. It is mentioned in photography that an aperture should be enlarged to avoid underexposure. What's the difference between one aperture and another?

This first gear refers to a fixed increment value, which is an increase in the amount of light, not a simple digital increase.

A higher gear will double the amount of light, but the aperture value will not increase several times.

Simply put, if the exposure is insufficient, it is necessary to increase the amount of light. If the aperture is larger, the light will double. To understand this problem, we must not involve the aperture value.

If you have played with a manual camera, you will know this aperture meter. Don't look at your numbers or the values on automatic machines. That's more accurate, but not doubled.

f 1； 1.4; 2; 2.8; 4; 5.6; 8; 1 1; 16; 22; 32; 44; 64