What is the exposure in photography?

Exposure refers to the process that the light emitted or reflected by the photographed object is projected onto the photosensitive film through the camera lens, causing chemical changes and development.

In photography, exposure is the combination of aperture and shutter.

It can be considered that the aperture (numerical value) is actually how big the small round window is, and the shutter (speed) is how long the window has been open. Assuming that the window is only open for 1/4 4 seconds, it is obvious that if the window is half open for 2 seconds, the film can be exposed correctly, because1/4 * 4 =1/2 * 2 =1,and the light input is the same. Similarly, if the window is fully open, the exposure time only needs 1 second. If the aperture of a lens is F4, and in photographic terms, the shutter speed of F4 is 1 sec, which is the correct exposure value, then F5.6 and 2 seconds, F8 and 4 seconds can also get accurate exposure pictures. Important conclusion: A correctly exposed photo can have n different combinations of aperture and shutter speed.

To sum up the explanation of the above terms, there are three factors that can affect whether a picture is exposed correctly: aperture, shutter speed and ISO (sensitivity). Among them, aperture and speed jointly determine the amount of light entering, and ISO determines the photosensitive speed of ISOCCD/CMOS. If the light input is not enough, we can open the aperture or slow down the shutter speed, and if not, we can increase the sensitivity (ISO). The disadvantage of large aperture is that the resolution is not as good as that of middle aperture. If the shutter speed is reduced, the picture may be pasted, and the quality of the picture will also decrease after the ISO is improved. Without a perfect plan, how to choose should be flexible.