Article - Photography Tips - Depth of Field and Aperture Explained

Click to view examples of a range of apertures used to take this shot.


Click to view examples of a range of apertures used to take this shot.


Looking through a camera lens; this is a small or narrow aperture of f22.


Looking through a camera lens; this is a medium aperture of f8.


Looking through a camera lens; this is a large or wide aperture of f2.8.

	> f2.8 > wide aperture > shallow depth of field (less in focus)
	> f5.6 > wide aperture > shallow depth of field (less in focus)
	> f8 > medium aperture > normal depth of field
	> f11 > medium aperture > normal depth of field
	> f16 > wide aperture > deep depth of field (more in focus)
	> f22 > narrow aperture > deeper depth of field (more in focus)

Depth of Field

Depth in the world around us

When you look around at the world, you notice that everything exists on different planes of view, or at different depths. There are objects in the foreground, objects in the background, and objects in the middle ground. Your eyes adjust their focus depending on what you are looking at.

Depth in photographs

Cameras have to go through the same process. If you have ever played with a fully manual camera, you will notice you must turn the focus ring on the lens to bring things into focus.

When we take photographs, they exhibit that same depth, just like in real life. The camera has to be focused on a particular object or at a certain point in the scene, whether that be;

• the foreground;
• in the middle of our field of view;
• or in the background.

The term“depth of field” is used to describe the zone of focus that is evident in front of, behind, and all around the object.

Introducing Aperture

In its most basic form, aperture is the size of the hole in the lens of the camera that determines how much light is let into the camera and onto the film or CCD in a digital camera.

How large this hole needs to be is determined by the conditions of the photo. In bright sunlight, the aperture (size of the hole) does not have to be very large, as the light has much more intensity.

In low-light conditions, the camera needs to get as much light onto the film or digital receptor as possible to make up for the lack of intensity of the light, so aperture must be wider.

Aperture settings

Aperture settings can be quite confusing until you get used to them, as the are the opposite of what seems logical! The best way to remember it is that the larger the hole, the smaller the number.

Most lenses have apertures in the range of f3.5 (which is the largest hole), to f22 (which is the smallest hole), with steps (called 'stops') in between, usually following the format of f3.5, f4, f5.6, f8, f11 and f22. Some professional lenses have an increased range of aperture settings, sometimes as wide open as f1.2 or as small as f32!

Often newer cameras have steps in between as well.

How aperture relates to depth of field

The aperture setting you use also effects something called the 'depth of field', as well as the amount of light that is let through the lens. This is an interested by-product of the optics used in lenses.

Above we discussed what depth of field means. Now comes the missing link - how does this relate to what aperture you use?

Basically, the wider the hole in the lens is (which equates to a 'large' aperture of say f3.5), the LESS will be in focus around the spot that you are actualy focusing on when you compose the shot. The opposite effect occurs when you use a 'small' aperture (small hole, big number - say f22) - there will be MORE of the shot in focus around the spot you are focusing on.

How you can use this in your photography

Well apart from all the exposure considerations I have talked about, there are other reasons why you might want to alter the aperture and create various depths of field when taking a photo. Depth of field might make the difference between an average photo and a really good photo.

Shallow depth of field

is good for focusing the viewer’s attention on one particular part of a photo, isolating a particular object and blurring out unimportant or distracting details such as things in the background or foreground. How often have you taken a photo of someone and had a lot of distracting details in the background which are in focus – such as tree branches and power poles appearing to protrude from people's heads?
So among other things, shallow depth of field (which is wide open 'big hole' aperture like f2-f5.6) is good for:

• Portraits
• Artistic effect – selective focus on a part of an object

Deep depth of field

is good for showing the full detail of the image, no mystery out of focus sections so everything in the image is clear and sharp. You may have wanted to take a photo of a group of children running around a playground, and you have focused on one child and all the other children are blurry!
So deep depth of field (apertures such as f16-f22 - a 'small hole') is good for:

• Group shots of people
• Landscapes
• Buildings
• Product shots

How to adjust aperture on your camera

Most cameras these days are fully automatic – however most older cameras and some newer more expensive ones do have some manual or semi-manual settings that you can play around with.

There should be a setting on these cameras called “aperture priority mode”, often labelled as 'AV' or 'A' mode on the camera's setting dial.

By putting the camera in aperture priority mode – it means that WE select the aperture that we feel would best suit the image (using the knowledge you have learned in this article), and the light meter in the camera does the rest by selecting the correct shutter speed so the film still gets the right amount of light to be correctly exposed.

So it’s basically a foolproof way to get some input into the way the image looks in the end – but by still getting the correct exposure.