The aperture setting on your camera works with the ISO and shutter speed settings to control the amount of light exposed onto the image sensor when you take a photograph. The lens aperture refers to the size of the opening on a camera lens and is measured in F stops with low numbers referring to a wide aperture e.g. F2.8 and high numbers referring to a narrow aperture e.g. F22, this can be a little confusing to begin with!
The size of lens aperture you choose to use will determine how much of your image is in focus, this area is referred to as “depth of field”. The wider the aperture, the shallower the depth of field will be and vice versa. I’ve used two photographs to illustrate this point. The top image was taken at F2.8, the lemons are clearly in focus (and your eye is immediately drawn to them), whilst the rest of the image is out of focus. The bottom image was taken at F22, the lens is focused in exactly the same place on the lemons, but because the depth of field available with a small aperture is so much greater, far more of the image is in focus. From a creative point of view, the second image is pretty poor because there’s no particular point of interest to draw the eye. Using a shallow depth of field and carefully selected focus helps to isolate the principal subject and create a more artistic looking image which is why it’s the creative tool of choice for food photographers.
Whilst using a wide aperture is great for close up and macro photography, it’s not much use if you want to include a wide range of detail in a photograph. Taking landscape photographs for example requires the smallest aperture setting possible to ensure the whole image is in sharp focus. Using a smaller F stop restricts the amount of light let in through the lens aperture, so this means possibly using a slower shutter speed (you’ll need a tripod) and/or a higher ISO setting to compensate for the loss of light. For every day photography such as taking pictures of your children outdoors, F8 is a good aperture to select as it will ensure that what you want in focus is, without having to make too many changes to your other settings.
If you’d like to learn more about using aperture for creative effect and how to combine it with ISO, shutter speed and selective focusing to improve your photography, please come along to my “Focus on Photography” course. You can find more details about this by clicking here.