What does "EV" mean when the camera on the mobile phone plays an adjusting role?

"EV" means: exposure value, which is a numerical value that represents the light passing ability of a photographic lens by the combination of shutter speed value and aperture value.

1. In the exposure process, it is usually expressed by the combination of shutter speed (t) and aperture value (f). For simplicity, it used to be expressed by light value (LV), but now it is expressed by EV. EV is the abbreviation of English Exposure Values, and it is a quantity that reflects the degree of exposure. Initially defined as: when the sensitivity is ISO 100, the aperture coefficient is F 1, and the exposure time is 1 s, the exposure is defined as 0, the exposure is reduced by one step (the shutter time is halved or the aperture is increased by one step), and the EV value is increased by 1.

2. Every increase of 1 in exposure value will change the first exposure, that is, the exposure will be halved, for example, the exposure time or aperture area will be halved. This may cause confusion. The reason for the decrease, rather than the increase, is that the exposure value reflects the setting of camera shooting parameters, rather than the illumination of the film (mentioned in the next paragraph). The increase of exposure value corresponds to a faster shutter speed and a larger F value. Therefore, a bright environment or a higher sensitivity (commonly known as ISO) should correspond to a larger exposure value.

3. Like traditional cameras, the photometric exposure system of digital cameras has a very basic principle when processing images, which is to restore all subjects according to the neutral gray brightness of 18%. Therefore, in the photographic system of the camera, no matter what the original brightness of the object is, it should be displayed in a medium brightness tone at last. Therefore, in actual shooting, the photographer still needs to make corresponding judgments according to the complexity of the shooting scene, and only in this way can the ideal density and color reproduction be guaranteed.