Understanding exposure can be confusing, so allow us to break it down and start with the basics. When taking photographs, an image is recorded by light reaching your digital camera’s sensor.
Like filling a bath with water, you need a certain amount of light to create a successful exposure; too little or too much can be a disaster. To regulate the amount of light reaching your sensor, the length of an exposure is controlled by two key components: aperture and shutter speed.
The aperture in your lens is equivalent to how far the taps are opened on the bath; the shutter speed is how long the taps are left running.
A wide aperture lets in more light, a narrow aperture lets in less light (find out when to go wide and when to go small).
Meanwhile, the shutter speed you choose will determine the length of time the light hits your sensor.
The aperture and shutter speed work in unison to take the exposure – and you can adjust one to suit the other.
You can choose a wide aperture, such as f/4, or a narrow aperture, such as f/16. And you can choose a slow shutter speed, such as 1/8 sec, or a fast shutter speed, such as 1/1000 sec.
There is an additional variable that effects exposure, and that’s ISO. The lower the ISO, the more light is required to record the image – using the above analogy, think of it as the size of the bath (find out when is best to increase ISO).
While ISO isn’t used as extensively as aperture/shutter speed to control exposure – ideally you want to keep it as low as possible as image quality degrades the higher you go – higher ISO is useful in low-light conditions (find out how to reduce noise at high ISO settings).
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