UNDERSTANDING EXPOSURE TRIANGLE: APERTURE, SHUTTER SPEED & ISO
A photograph’s exposure determines how light or dark an image will appear when it’s been captured by your camera. Believe it or not, this is determined by just three camera settings: aperture, ISO and shutter speed (the “exposure triangle”). Mastering their use is an essential part of developing an intuition for photography.
Achieving the correct exposure is a lot like collecting rain in a bucket. While the rate of rainfall is uncontrollable, three factors remain under your control: the bucket’s width, the duration you leave it in the rain, and the quantity of rain you want to collect. You just need to ensure you don’t collect too little (Underexposed), but that you also don’t collect too much (Overexposed). The key is that there are many different combinations of width, time and quantity that will achieve this. For example, for the same quantity of water, you can get away with less time in the rain if you pick a bucket that’s really wide. Alternatively, for the same duration left in the rain, a really narrow bucket can be used as long as you plan on getting by with less water.
In photography, the exposure settings of aperture, shutter speed and ISO speed are analogous to the width, time and quantity discussed above. Furthermore, just as the rate of rainfall was beyond your control above, so too is natural light for a photographer.