One of the technical goals of photography is to create a properly exposed image. There is no way to achieve this other than knowing how much ambient light is on hand and how much creative latitude you have in that light. Exposure metering is how you get this information. By using either an internal or external exposure meter, you can measure the brightness of the subject or its surroundings.
It’s important to become familiar with how exposure meters work and the different ways to gather a reading, because ...