Exposure is fundamental to making photographs. Understanding the concept of exposure triangle will make you a better photographer. This simple concept has been talked about a lot of times but rarely do you find a photographer, experimenting and analyzing results based on this triangle.
There are three main elements that exists on any DSLR camera, Aperture, Shutter, and ISO. Understanding how these work and using them together will allow you to be more creative that using the standard “auto” setting on your camera.
The Aperture controls the size of the opening in your lens and is denoted as f/2.8, f/4 and so on. The higher the number, the smaller the opening and thus less light is let in.
Each full stop of the aperture either doubles or halves the size of the lens opening (depending which direction you’re adjusting). In order to get the same exposure, the shutter needs to adjust for the lens opening. The table below illustrates the aperture and shutter combinations to achieve the same exposure. Think of it this way, if you double the size of the opening (each f/stop to the left on the table), the shutter speed has to double as well.
Remember, the smaller f-number represents a wider opening in the lens and thus more light is let in. The way to counteract it is to increase the shutter speed or increase the ISO. Each element is codependent on the other.