One of the easiest ways to improve our portraits is by creating beautiful background blur. It’s a great effect because it creates a clutter free background, which is essential in making sure our subjects pop!
You need to be shooting in manual mode to get those blurry backgrounds on purpose! So if you’re not, familiarise yourself with the exposure triangle and jump in!
Related: Getting out of Auto
But if you are shooting in manual mode already, then you’ll know you need a wide open aperture to get those blurry backgrounds. And this is where people run into difficulty when it comes to taking large group photos…
So how do we get all our subjects in sharp focus? How do you know what aperture to use? And how do we do that and get a blurry background?
Let’s have a look a closer look at aperture, so that you can confidently decide which combination of settings will suit best next time you’re photographing an extended family or a large group of people.
Aperture is one of the three elements that controls exposure in your camera, and it also affects your depth of field.
It refers to the physical opening of your lens, and is measured in f stop (eg. f/1.8, f/3.5, f/11 etc).
Related: What is The Exposure Triangle
Depth of field is the area of focus in front of and behind the point where you focused (that would be your subject!).
How much depth of field you have is controlled by your aperture setting. Remembering aperture is measured in f stops:
We use wide apertures for blurry backgrounds, such as an image of a flower or person and then everything behind it is out of focus.
A narrow aperture is used for images where we want everything from front to back to be in sharp focus, such as a landscape image.
Then there are the variations in between as we open up and shut down our apertures… see our very technical diagram!
You can see in our beads example below… at f/2 (known as a wide aperture) we have only one bead in focus.
When we increase the f stop to f/8 (also known as stopping down or closing down the aperture) we have more beads in focus behind the bead that we focused on.
Now lets imagine our beads are the heads of an extended family grouped together! We want to ensure all our people in a group will be clear and in focus.
I get asked this question often, and the answer is not what you’d expect!
When you focus on a subject everything to their side is on the same focal plane, and will also be in focus. So this means if you’re taking a large group photo and every person is standing side by side in a straight line, and you were standing directly in front of them, they would all be in focus at a wide aperture. Whether the group was 2 people or 50 people!
Because the issue here is depth not width, or focal plane in photography speak.
In this graphic everyone would be in focus regardless of aperture because they’re all standing next to each other… ie. on the same focal plane!
And here’s a real life example… a family of four all sitting pretty much on the same focal plane, shot at f/2.8 and all in sharp focus.
Outside of that focal plane, you will see a gradual reduction in focus in front and behind the subjects. So when taking photos of groups with people several deep, you need a deeper depth of field to ensure everyone is in focus from front to back.
And we adjust that depth of field by closing down the aperture (increasing f stop number). This family were photographed with an aperture of f/5.6 because they’re sitting on roughly 3 separate focal planes. The deeper your group of people, the more depth of field you need to get them all in focus.
Conversely, this extended family with far more people than the image above, was shot at f/4.5 but everyone is in focus because they’re sitting on just 2 focal planes.
In manual shooting, aperture controls depth of field. But it’s also affected by focal length, the distance between lens and subject, and even your camera model. So to give you an exact f stop that works for every situation would require knowing all those variables each time.
There are depth of field calculators online, however it’s not exactly practical to pause between every shot to calculate!
I personally think it’s easier to simply pick a generous but not over the top aperture, take a shot, zoom in a little on your LCD screen and scroll around to check everyone is in focus.
Try these settings as a starting point, and from there you can adjust:
2 people deep / 2 focal planes) – f/4
3 people deep / 3 focal planes) – f/5.6
4 people deep / 4 focal planes – f/7.1
…and so on.
If everyone in the group is not in focus, adjust your aperture to a higher f-stop, and check again.
Don’t be looking for tack sharp faces because once you’re zoomed all the way in. You’re in pixel peeping territory and a loss of sharpness is normal.
Out of focus is different, it looks a little like motion blur.
Once you start getting into bigger groups of people, say 15-20, you want to try to keep them to 3-4 focal planes so that you don’t have to shoot at apertures that will put the entire scene into focus and thereby lose any bokeh whatsoever!
As depth of field recedes in front and behind the point of focus, the best technique is to focus on someone in the middle focal plane.
Now we know that the narrower the aperture, the more our background comes into focus. So how do we get everyone in focus, and still ensure beautiful blurry backgrounds?
Remember we said depth of field is not only affected by aperture, but also by distance between subject and background, and your lens focal length?
So an easy way to get a blurry background is by putting a lot of distance between your subjects and the background. In this image below the subjects were about 3-4 metres from the garden behind them.
The second thing you can do is use a longer lens, because long focal lengths compress the background.
The image above was taken with my 135mm lens which gave me a beautiful background bokeh.
Related: Lou’s Favourite Lens
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