Learn Photography Tips Blog

How To Blur The Background

// April 11th, 2010 // How To...

If there’s possibly one thing that makes a photo stand out as being ‘pro’-like, its the fact that the subject of the photo  – whether this be a person, a dog, a football or whatever – is in focus, whilst the background is a blur. This ‘blurred background’ is probably the major difference between pro-quality photos and most people’s holiday snaps – it really is that effective.

And it’s easy to do!

It really comes down to the use of aperture, focal length and focus distance – all of which may sound pretty technical if you’re new to photography, but it’s really not complicated. Aperture is simply talking about how much light enters your camera, focal length just means how long your lens is, and focus distance just means how near you are to the object you’re focusing on. I’ll go into more depth on how controlling all of these factors means you can get that blurred background look below – and though this is probably easier to achieve if you have a DSLR camera, if your compact has the ability to manually choose the aperture and focal length, then it will apply to you too.

Aperture

As mentioned above, when we talk about ‘aperture’, we’re meaning how large the opening on your lens can go, and thus how much light can enter your camera at once.  I could go on about how different lenses have different apertures, and the correlation between f numbers and so on, but I want to make this ‘blurring the background’ business as simple as possible so that you can give it a go right now – if you want to learn more about the technical side of aperture, I’ll go into that a bit later in this guide (including how you can imagine aperture to be like icing a cake (!) – or you can visit Wikipedia’s entry on aperture).

So, to get that blurry background look by controlling your aperture, simply:

1. Choose ‘Aperture Priority’ mode on your camera (this is ‘Av’ on Canon cameras, or ‘A’ if you’re using a Nikon)
2. Adjust the aperture so it shows the smallest f-number – this will probably be f3.5 to f5.6, although some lenses go as low as f.1.2 (you use the dial on the top-right of the camera on Canon SLRs to do this)
3. Focus on your subject, and take the photo!

See the below example of how controlling the aperture gets us that lovely blurred background – the photo on the left taken with a low f-number (f/4.5), the photo on the right with a high f-number (f/16):

Aperture: The Technical Stuff As A Cake-Decorating Analogy

By choosing a large aperture you obtain a shallow ‘depth of field’, hence the blurred background. Objects in the foreground – in front of the subject, between the subject and the camera – would also be blurred.

The technical reason why a large aperture results in a shallow depth of field is, well, very technical – but you can think of it this way, with a cake-decorating analogy: When you have a large aperture, it means you have a large lens opening – this is like dumping a load of icing on top of a cake using your hands, just throwing it on. A good amount of icing will fall where you want it to go (the focus on your subject), but a lot will also be scattered and splurged around the rest of the cake (the blurred background/foreground):

On the other hand, choosing a small aperture means you have a small lens opening – this is like using a fine pipette to apply your icing to the cake. All of the icing will be placed exactly where you want it, and look perfect – meaning your entire photo will be in focus, with no blurring of the background/foreground:

Sounds strange to mix cakes and photography, but it works for me!

Aperture can be doubly confusing, because when we talk about a larger aperture, we actually mean a smaller f-number (such as f/3.5) – and, conversely, a smaller aperture means a larger f-number (like f/16)! So, if you get confused by the f-numbers then an easy way to remember is:

If you want more Focus, you want more F-numbers

Obviously, this guide is about getting a blurry background, so we’ll be wanting low f-numbers please…!

Focal Length

Another way to achieve a blurred background is to use a longer focal length – so, to put it simply, using a telephoto lens ‘racked out’ at its maximum length (perhaps 200mm or larger) is going to give you a blurrier background than a normal zoom at its widest length (say, around 18mm). If you’ve just bought your first DSLR, and are still using the kit lens that came with it (that can only probably zoom as far as 55mm), you may want to think about investing in a telephoto zoom just for this reason (I use the Canon EF-S 55mm – 250mm, which you can get from Amazon US and UK).

In the two examples below, I used the exact same camera and exposure settings, but with two different focal lengths – the left photo taken with a 55mm focal length, the right with a longer 109mm.

Focus Distance

The final thing under our control is the physical distance from our camera to the subject – and it’s a simple rule to learn:

The closer the point of focus, the greater the background blur.

I’ve showed this in action with the two photos below. Both shots were taken using the exact same camera, exposure, and focal length settings, but I (and thus, the camera and point of focus) was further away in the left shot, and closer in the second:

Final Thoughts

I hope you’ve enjoyed this little guide, and that it helps you get those lovely blurry backgrounds. If you’re interested, all of these photos were taken with a Canon 500D (known as the T1i in America) which is available from Amazon UK and US.

The beautiful model is my wife, unfortunately not available on Amazon!

Ooh, and seeing as you made it right to the bottom, perhaps you’d like to follow me on twitter too?