Learn to master depth of field

THE MISSION

To explore the effect depth of field has on a portrait

Time: 30 minutes

Skill level: Beginner

Kit needed: D-SLR

As we all know, aperture affects depth of field: a wide aperture, like f/1.4, will give you a very shallow depth of field, where not much in front of or beyond the focus point is sharp, whereas a narrow aperture like f/16 will give you a much greater depth of field. 

On any lens you have multiple aperture settings to choose from, and you might find yourself wondering which aperture to use, and which is the best. Put simply, there isn’t one ‘best’ aperture. 

By following this walkthrough, you’ll soon learn how to decide which aperture you need for any given portrait shoot, and how to set it with confidence. We’ll show how setting a very wide aperture can really help your subject stand out from a busy and distracting background, but we’ll also show how to keep your background sharp if you do have a backdrop that  complements your subject. We’ll even show you some useful kit you might want to invest in to get more creative with aperture.

STEP BY STEP: Find the right depth

1 PICK A GOOD SPOT 

As you’re going to be experimenting, find a location that has two or three different backdrops. It’ll reduce your need to trek around. We chose a corner of England that has just that – a busy background in one direction, and a simpler background in the other.

2 KNOW YOUR LENSES

Both focal length and aperture impact on the depth of field. Wide-angle lenses tend to give good depth of field, even at quite large apertures. Telephoto lenses do the opposite, giving narrow depth of field even at quite small apertures.

3 KEEP THINGS SIMPLE

Make it easy for yourself: set aperture-priority on your mode dial and Auto ISO in your camera’s menu. In Auto ISO set a minimum shutter speed of 1/200 sec (not all camera's have this feature; use a tripod if yours doesn’t). Now the only setting you need to change is the aperture.

4 BLUR OUT DISTRACTIONS

Our first backdrop is full of daffodils, and all that texture and detail is a bit distracting. Set your lens to its widest aperture (this could be f/2.8, or f/4, or similar) to blur out the background but keep your subject sharp. Now the model stands out from the backdrop!

HOW WIDE IS TOO WIDE?

Sometimes shooting too wide results in an unusable depth of field. Setting, say, f/1.4 or f/1.8 on a 50 or 85mm lens makes the depth of field so limited that you will struggle to get both eyes in focus at the same time, unless they’re on precisely the same plane of focus. 

In cases like this, you might want stop down to, say, f/5.6 or f/8, to ensure both eyes are sharp, while still blurring out the background.

5 INCLUDE BACKGROUND INFORMATION 

Next, set your model against a backdrop where you want to retain lots of detail, such as the intricate church facade here. Set your lens to a higher aperture value – we used f/11, but anything from f/8 to f/16 will work – to ensure both the subject and background are in focus. 

6 MOVE YOUR SUBJECT 

The closer your subject is to the lens, and the greater distance between your subject and the backdrop, the narrower the perceived depth of field. Experiment by moving your subject closer to the camera and further away from the background, and vice versa. 

KIT BAG ESSENTIALS: ND filters

1 TOO BRIGHT TO GO WIDE...?

Midday sun can be very bright, to the point where you might not be able to set a wide aperture. At ISO100 and 1/8000 sec we had to go up to f/8 for a correct exposure here, but this meant the background was distracting. A neutral density filter is what was needed.

QUICK TIP!

Attaching an ND filter can make the image in the viewfinder quite dark, making composition more of a challenge. For a clearer view, try draping a sweater or jacket over your head and camera while you’re shooting, to make the viewfinder image brighter.

2 ...ATTACH AN ND FILTER!

An ND filter basically reduces the amount of light entering the lens. With a two-stop ND attached, at f/8 our subject was way to dark, so we had to open up the aperture to f/4 to let in more light. This wider aperture gave us the blurred background we wanted.