How do I use the +/- scale of the light meter in my camera?

Question

I have just recently used the metering scale. I assume that if the scale arrow points in the middle, this means that the camera detects that the current exposure settings are the "right" ones.

However, I assume there would be times when you want to go above or below the middle point in the scale. The problem is, I do not know what those situations are. So, what are those situations?

As a side question, what does the -1 and +1 or -2 and +2 mean here?

Answer

The metering scale you are referring to is used for two things.

In manual mode (M), it indicates how far you are from what the camera thinks should be the right value. It is the camera's guess (depending on the metering mode, see other questions in metering).

In all other modes, it is called exposure-compensation (EC) and is you telling the camera to adjust its measurement to something brighter or darker.

In general the camera meters so that the scene is on average of average brightness. By doing over the metered value, you are telling the camera you want something brighter and by going under the value you are telling you want something darker.

The metering scale is measured in EV (Exposure Value) where each full-step represent a doubling of brightness. So +1 is twice as bright, +2 is 4 times as bright and -1 is half as bright, etc.

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