Famous photographer Bryan Peterson in his book Understanding Exposure explains the concept of exposure in photography easily. Peterson illustrates three elements that must be known to understand exposure, he named the three relationships as a Photography Triangle. Each element in the photographic triangle is related to light, how light enters and interacts with the camera. You definitely need to learn these basics, especially before you try the more advanced fields in photography, just like the wedding and boudoir photography.
These three elements are:
ISO – a measure of how sensitive the camera sensor is to light
Aperture – how much the lens opens when the photo is taken
Shutter Speed – the “window” time frame in front of the open camera sensor
The interaction of these three elements is called exposure. Changes in one element will result in changes in other elements.
The parable of Exposure Triangles
Perhaps the easiest way to understand exposure is to give a parable. In this case, I like the parable of the exposure triangle as well as a water tap.
Shutter speed for me is how long we open the tap.
Aperture is how wide we open the tap.
ISO is the strong impulse of water from the water company.
While the water flowing through the faucet is light received by the camera sensor.
Certainly not a perfect parable, but at least we get the basic idea. as you see, if exposure is the amount of water coming out of the tap, it means we can change the exposure value by changing one or a combination of the three constituent elements.
You change the shutter speed, which means changing how long the tap is open. Changing the aperture means changing how much the water discharge, while changing how strong the water pushes from the source. Changing the ISO on the camera means changing the size of the water pressure.