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Published on 20 Jan 2014 | over 2 years ago

How to create a blurred background in portrait shots. A guide for the DSLR user on the factors that influence background blur: aperture, the distance from subject to background, the distance from camera to subject, and the optical length of your lens.


Hi, this is Tom Greenwood from sydneyportraits.com.au .

Now in this clip we're looking at how to create that lovely blurred effect in the background of your portraits.

There are four main factors affecting the amount of blur you create in the background of your shots.

The first is the aperture that you use, the second is the distance between the subject and the background, the third is the distance between the camera and the subject and the fourth is the kind of lens you use, be it a wide-angle, a normal lens or a longer lens.

First let's look at aperture. Now we're in the park and our subject is two or three metres in front of the rocks that make the background. Here we're shooting at 50mm. Now this first shot uses an aperture of f11, a fairly small aperture and as you can see there's an element of blur, but not very much.

If we take the same shot at f4, which is a fairly wide aperture, we can see the background is quite nicely blurred and the subject stands out in contrast. So the wider the aperture, the narrower the depth of focus and therefore the blurrier the background.

So let's have a look at the distance between the subject and the background. In the first shot the subject is the same two to three metres from the rocks. And now, using the same 70mm lens and the same aperture of f5.6, the subject is less than a metre from the background. So, clearly the greater the distance between the subject and the background, the more blurred the background will be.

Now let's look at the distance between the camera and the subject. Both of these shots are shot at 40 mm with an aperture of f5.6. The first shot was taken from about two and a half metres from the subject and this shot, about one and a half metres.

Now it's not the most dramatic example but you can clearly see the more blurred background the closer you, the photographer, are to the subject.

Now let's have a look at the optical length of the lens. So once more our subject is about two or three metres from rocks and the aperture is f5.6 in both shots.

Now this is shot at 24mm, so quite wide. Now this is shot with a much longer lens at 70mm. You can see the difference in perspective — also the increased blur with the 70mm lens.

Finally lets put together a number of these factors. Here we're using an 135 mm and the trees in the background are quite a distance away, something like half a kilometre.

This shot uses an aperture of f11. Whereas here we switch to f2.8. Our subject is lovely and crisp, and the background has that beautiful soft, blurry texture.

I hope you found this clip useful. Please leave a comment and take a look at some of the other clips in the series. Good luck and happy snapping!

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