Light ratio control and light ratio calculation in portrait photography

Calculation of light ratio 1:2|EV2-EV 1| The above formula is square. When ISO= 100 F/ 1.0, the time is 1EV = 0. EV refers to changing aperture or shutter or ISO, also called step size, 1 step size.

Or: double the brightness, increase EV by 1, and increase one step. The brightness is reduced by half, and the EV is reduced by 1, which is one step lower. For example, F5.6-F81125s-1/60s.

The control is as follows: the EV value can be measured directly with an exposure meter. Usually we measure the aperture in the studio. For example, the difference between the bright part and the dark part of the face.