Let’s analyze the aperture priority in specific numbers
Let’s say ISO (sensitivity) 200. Lighting is sufficient. We set the aperture to f2.8 (that is, the aperture is fully open). Then the camera sets the shutter speed so that the exposure is correct. In this case, the shutter speed is 800.
Why change the numerical value of the aperture
In other words, for which purpose the diaphragm opening is clamped or opened. The fact is that the aperture controls the depth of field. That is, the depth of the blur. If there is one person in the frame, then the aperture can be opened completely. If there are several people in the frame, then it is necessary that everything in the photograph turns out sharply. In this case, the diaphragm must be covered.
Aperture priority mode is much more convenient to use instead of full manual mode, because that way you have to control one less parameter. In manual mode, you have to control shutter speed, aperture and ISO. Therefore, aperture priority is most convenient for shooting when the lighting changes often so as not to bother with settings and less often access the camera menu.
I hope I did not confuse you … The main thing is to read it carefully, and you will understand everything. If you have any questions, write in the comments. If everything is clear, and the article was useful to you, I will be grateful if you share it with your friends.
There is also a camera simulator specially for you. You can practice yourself to understand the principle.