What is the EV value? How to calculate EV value

ExposureValue: A numerical value that represents the light passing ability of a photographic lens by the combination of shutter speed value and aperture value. Exposure is usually represented by the combination of shutter speed (t) and aperture value (f). For simplicity, it used to be represented by LightValue(LV), but now it is represented by EV. EV is the abbreviation of English ExposureValues, 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 reduced by one step), and the EV value is increased by 1. Calculation of EV value: Assuming that the aperture value is set as f and the shutter speed is t, there is the following relationship: EV=3.322log 10(f×f/T) Every time the exposure value increases 1, the exposure will change by one step, that is, the exposure amount 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. 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.