There are three main elements to exposure – aperture, ISO, and shutter speed. And, the relationship between these three elements can be thought of in terms of the ‘exposure triangle’. Each corner of the triangle represents one of the three main elements.

These three elements are all related and directly affect the exposure. One way to think about how these elements work together is to as imagine trying to fill a bucket with a garden hose:

ISO – is the measurement of the image sensors sensitivity to light. The amount of water in the bucket represents ISO, or the amount of light needed to achieve the proper exposure.

Aperture – is the size of the lens opening when the photo is taken. Imagine that size of the hose’s opening is the aperture.

Shutter speed – the amount of time the shutter is open. The time the hose is left on is the shutter speed.

All of these elements are directly related to each other.  If you decrease the size of the hose opening (aperture), then you need to increase the amount time the hose is on (shutter speed) to fill the bucket with the right amount of light (ISO).