What Is Aperture In Photography?

What exactly is an aperture in photography? An aperture is the opening within the lens on your camera. Depending how much the aperture opens determines how much light can pass through the lens and hit the sensor/film.

A good way to think of this is look at someone’s pupil when in a dimly lit room. Our pupils open up to let in more light – the aperture in your lens works in the same way.

But aperture doesn’t just control how much light gets into your camera, it also controls how much of your photo will be in focus – this is called depth of field (see photos further down the page).

When using your camera in automatic mode it will choose the aperture and shutter speed needed to make a decent exposure. To change the aperture set your camera to aperture priority mode. This setting allows you to choose any aperture you wish and let the camera select a shutter speed to make a good exposure.

Let’s take a look at what’s happening in the lens when you change the aperture.

F-Stops

Aperture is measured in what’s called F stops (you will hear this referred to as F number). Now don’t get too worried. Where ever you see a number with an F before it like f2.8 this just means that is the size of the aperture in the lens.

The lower the F number like f2 the wider or larger the aperture opening is in the lens. So of you have an aperture of f16 the hole in the lens will be very small and only let a tiny amount of light pass through.

This does sound confusing especially hearing it for the first time but it doesn’t take long to get familiar with it.

Aperture and depth of field

So you have your camera in aperture priority mode and have selected an aperture of f2.8. You take a picture and realise part of it is in focus but not all.

This is because the aperture not only controls how much light gets in the camera but it also controls how much of your photo will be in focus (this is called depth of field).

Look at these photos taken at different apertures.

As you can see the wider the aperture the less of our photo will be in focus (called shallow depth of field).

While on the opposite end when we have a small aperture like f16 there is a lot more of the photo in focus (larger depth of field).

Aperture and shutter speed

So you now understand that when we use a low f number like f1.8 this lets a lot of light into the camera and therefore the camera will need to increase the shutter speed to counter this and make a properly exposed picture. Oppositely if we use a high f number like f16 the camera would need a slower shutter speed to allow more light to pass through the lens to make a proper exposure.

Have a play around with your camera in aperture priority mode and see how the camera increases the shutter speed as you select a wider aperture (low f number don’t forget i.e f2.8). The more you practise the better an understanding you will build.

Why not go take some lovely portraits of a friend or loved one with a nice wide aperture to keep them as the centre of attention in the photo.

Take some nice close up detail shots next time you see some water droplets on a leaf or anything that catches your eye next time you’re out and about with your camera.

I hope that has given you an understanding of what is an aperture in photography.

If you fancy getting your camera out of auto and into aperture priority mode – check out this video.