Andrew Wood Photography

Welcome to the first in a series of articles intended to show budding photographers how they can create their own unique images. In this first installment we will be looking at using your camera in Aperture Priority mode so that you can control the Depth of Field in your photographs.

Have you ever wondered how you can take photographs with blurred backgrounds but with the subject in sharp focus? This is achieved with a narrow depth of field.

Depth of Field

“Depth of Field” is photo-geek speak for how much of an image is in sharp focus. It is the distance between how close an object can be to the front of the lens (near focus limit) or how far away it can be from the front of the lens (far focus limit) and still be sharply focused.

This image uses wide aperture / narrow depth of field to blur out distractions, including (to a degree) the foreground mesh fencing and background machinery.

Using a narrow depth of field means that the distance between near and far focus limits is small so that anything in front of or behind the subject appears blurred. It’s possible for depth of field to be so narrow, that an eye can be in focus but other facial features like eyebrows, noses and ears are out of focus.

A photo taken using a wide angle lens and a narrow aperture (wide depth of field) gets both the background and foreground elements of this image into reasonably sharp focus

A wide depth of field means that the distance between near and far focus limits is large – objects in front of and behind the subject will appear in sharp focus.

There are two things that give you  control over depth of field, excluding your choice of camera. The first is aperture and the second is focus distance.

Aperture

The aperture is the opening inside the lens that lets light pass through it. It’s a bit like the pupil of the eye. In low light, the pupil opens up to allow more light to pass inside and reach the retina at the back of the eye. And in bright light it narrows in order to reduce the amount of light reaching the retina. This is why, when moving from being indoors to going outdoors, it can be uncomfortable whilst waiting for your eye’s pupils to close up. Too much light is allowed through the pupils which is slightly painful and that in turn causes you to squint or shade your eyes.

50mm f/1.4 lens with it’s aperture wide open – this would result in a narrow depth-of-field photograph.

50mm f/1.4 lens with it’s aperture stopped down to f/16 – this would result in a wide depth-of-field photograph.

When a camera is in automatic exposure mode it attempts to automatically adjust to the light levels in the scene you are photographing by changing both the aperture and the shutter speed. Just like human eyes, in low light the camera uses wider apertures (pupils) and in bright light it uses narrow apertures (pupils).

It’s possible to put the camera into aperture priority exposure mode. This means that you can choose the size of the aperture you would like to take photos with and the camera will in turn choose the other exposure settings for you. Keep reading for more detail on how you can do this.

The aperture selected not only affects exposure, but it directly affects depth of field. Wide apertures result in a narrow depth of field and narrow apertures result in a wide depth of field. This is something we explain in more detail on our beginners course, however you don’t need to understand any more than what’s written in this blog post to take advantage of it. There’s more explanation with some examples below.

Focus Distance

The focus distance is the distance at which objects will appear in the photograph in absolute precise focus. The depth of field determines how far in front of and behind the focus distance objects in the scene can be and still be rendered sharply in the captured image. If, for example, you photograph a person who is 5 meters away from the front of the lens, according to the chart below, any objects in the foreground more than 4.68 meters away from of the lens and any objects in the background less than 8.34 meters away will be rendered sharp.

For the photo-geeks reading this article, the chart is based on an APS-C sized (1.5x crop) sensor and an f/5.6 aperture. For more, have a look at the Cambridge in Colour tutorial on Depth of Field.

And if I’ve lost you there, don’t worry. The principal is simple. The further away your subject is, then the greater the depth of field you will have in your photograph. In other words, if you are struggling to get an out-of-focus background, then try moving closer to your subject.

Focus distances and DoF – f/5.6 on an APS-C sized sensor

Aperture Priority Mode

To use the aperture priority mode in your camera, move the exposure mode dial on the top of the camera so that is the  ”A” current mode. On some cameras it is marked “Av” instead. If you are not using a traditional dSLR, you may find that you have dip into one of the cameras on screen menus or use one of it’s function keys in order to put your camera into aperture priority mode.

The aperture priority exposure mode is indicated by an ‘A’ or ‘Av’ on the exposure mode dial atop the camera

Then, the next step is to choose your aperture. Aperture values typically look like:

f/1.4    f/2.8    f/5.6    f/11    f/16    f/22

The smaller numbers give a wide aperture and the larger numbers give a narrow aperture. (Actually, the numbers are fractions or ratios, so the bigger numbers are actually smaller fractions.. but lets not worry about that!)

The aperture can be selected using the jog wheel (command dial) which is usually handily located so that you can reach it with your index finger or thumb of your left hand when holding the camera.

The jog wheel (often called command dial) is located on the back of this dSLR camera – within easy reach of the right thumb. On other cameras it can be located in other places.

The selected aperture value can usually be seen on the back of the camera when using live view or, as one of the set of numbers displayed in green at the bottom of the cameras view finder.

If you are looking to blur the background, you will want to select the widest aperture you can. So on most lenses that will be f/5.6 – perhaps f/3.5 if you have the lens zoomed out.

Try setting the aperture to f/3.5 by using the command dial – if you can’t see this display (either on the LCD or in the view finder) try half pressing the shutter button to “wake” the camera up.

If you are using the kit lens (the one that your camera was supplied with) then you might find if you have zoomed in that the widest aperture is f/5.6

If you want to get the background as well as the foreground in focus (not always possible with short focus distances – see hyper-focal distance) then you will want to select an aperture of f/11 or f/16. Of course, using narrow apertures in low light situations, that may mean using longer shutter speeds and putting the camera on a tripod or boosting the cameras ISO (light) sensitivity – these topics are sadly going beyond the scope of this blog post, but we intend to produce a future article with guidance on taking photographs in low light.

Notice that to the left of the numbers on the display at the back of the camera, there’s a useful visual representation. This is useful for beginners, but as you get more experienced you may find that you turn the info display off completely and concentrate more on using the information displayed in the view finder.

The widest and narrowest apertures you can use are determined by the lens that you are using. Many keen photographers looking to take photographs with really controllable depth of field will invest in a nifty fifty. This is a 50mm lens (fixed focal length – it doesn’t zoom in or zoom out) with a widest aperture of either f/1.4 or f/1.8. These lenses with their wide maximum apertures not only help produce well exposed photographs in low light, but they tend to make really good portrait lenses too.

A Nikon 50mm f/1.4 AF-D Lens – Please note that if you have a Nikon D5xxx or D3xxx series camera then you will need the AF-S version. The f/1.8 versions are always cheaper than the f/1.4 versions.

As a final bit of help in understanding the relationship between aperture and depth of field, these pictures are intended to demonstrate the effect:

See how, with the wide aperture, the cardboard robot is extremely out of focus

In this variation of the cardboard robot/alarm clock photograph, we can see the Robot much more clearly. This photograph is taken at f/16 and being indoors, we’ve resorted to using to off camera flash to help light the scene. The sunlight from the foreground has completely disappeared as a result of the change in exposure settings.

Now it’s time to practice taking photographs using different apertures so that you can get used to what the results look like. When using a wide aperture, it’s sometimes necessary to be careful what the camera focuses on. You may need to look at choosing your focus point if using auto focus or instead switching over to manual focus and then focusing your lens by hand.

All of this and more is covered in the courses we offer and also by our one-to-one tuition. If you’d like to find out more about how we can help you, why not contact the studio? In the meantime whilst you look forward to more of our future articles offering photography hints, tips and advice here’s a slew of  both narrow and wide DoF examples.

Wide Aperture (Narrow Depth of Field) Examples

Narrow Aperture (Wide Depth of Field) Examples

Words and Pictures by Daniel Cadden on behalf of Andrew Wood Photography – Daniel is experienced commercial photographer and photography tutor and will be more than happy to answer your questions or take your suggestions on future topics in this Creative Photography Series. Just contact the studio using any of these details.