CAN YOU PLEASE EXPLAIN TO TO ME WHAT IS EV COMPENSATION AND HOW DOES IT WORK
EV compensation is "Exposure Value compensation". The camera contains an exposure meter which determines how much light is on the scene and sets the exposure appropriately. However, this meter does not know WHAT you're taking a picture of, nor does it know what effect you're going for. The best it can do is to assume you're taking a picture of an "average" scene and want it to be of "average" brightness. It does this by assuming the scene is "middle gray," halfway between black and white. Most of the time this works fine, because most scenes are, well, average.
However, this is not always the case. Suppose you're taking a picture of a white dog playing in the snow. Almost everything in the scene is bright white, but the camera doesn't know that. It tries to make the scene middle gray, and the result is that you get a gray dog playing in gray snow.
On the other hand, suppose you're taking a picture of a black cat sleeping on the hood of a black car. Here everything is black, but the camera doesn't know it. It tries to make an average scene, resulting in a gray cat sleeping on a gray car.
EV compensation allows you to override the camera's exposure setting. In the first example, you'd want to add two or three stops (positive EV compensation) to force the camera to render the dog and snow as white instead of gray. In the second example, you'd want to subtract a stop or two (negative EV compensation) to render the cat black instead of gray.
How much EV compensation is correct? Well, that depends on the scene. With a digital camera, you can look at the picture and see whether the dog looks white or the cat looks black. Film photographers take lots of shot, using various levels of EV compensation, so that one of them would come out right.