Exposure value is how we express and talk about exposure, so we need to make sure we know what exposure is in order to be able to give it a value.
Exposure is the total amount of light that you capture and record when taking a photograph.
You control your exposure through your ISO, Aperture, and Shutter Speed settings, which physically control how much light is able to enter the camera to be captured.
Generally speaking, when we’re choosing the ISO, Aperture, and Shutter Speed settings, we’re working to get the exposure indicator to zero.
We do that because the exposure indicator is connected to the camera’s meter, and the meter is the camera’s brain.
The meter reads the light in the scene, calculating the average brightness of that scene, and the goal of the camera meter is for that average brightness of the scene to be fifty percent.
Generally speaking, a scene that meters to an average brightness of fifty percent will be a well exposed photo.
So, the exposure is how much light we capture, and the value of that is tied to the camera meter and how it evaluates the scene.
That value is expressed as a number on the positive and negative scale of the exposure indicator.