How to blur backgrounds using the aperture

Over the past few months there have been many daily searches to this site about depth of field and how to blur backgrounds. Professional photographers use this technique and this post will address some of these actual searches to this site, such as “how to make the background blurry”, “what to I change to make blurry backgrounds”, “camera settings blurred background”, “how to change depth of focus”, “how do you change camera settings to make a fuzzy background” and “what f-stop do I use to blur the background of a photo”.

In this post I will outline the settings and factors involved in making the background or foreground of a photo appear out of focus relative to the in focus subject.

What is the technique called to make certain elements appear blurry or out of focus?

The technique is called Depth of Field or DOF in some articles. This depth of field is controlled by the f-stop on your camera.

What settings give greater depth of field?

Basically the lower the number the more exaggerated the depth of field. So f/1.8 would have a very obvious blurred background compared to f/22. You can use the “Aperture Priority” mode on your camera (if you are not totally comfortable with fully manual), with your subject a bit of a distance from the background (2 meters or more), and set your Aperture to an F-stop of 5.4 or smaller number. The smaller the aperture or F stop, the larger the aperture opening therefore increasing the light into the camera – in turn this affects the shutter speed allowing a faster shutter speed as more light is entering the lens as a result of the wider aperture.

When would you use f/1.8 and when would you use f/22?

You might use f/1.8 to select your subject and blur the background. If you want to take a portrait shot and the background might be uninteresting or even not that appealing – you could use a low aperture like f/4 (or f/1.8 is even better again) to make the subject in focus and the background out of focus or blurred. Similarly for landscape photos normally these would be shot between f/11 and f/22 depending on the lighting conditions and the desired effect. This ensure sharpness along the depth of the photo.

Is there any relationship between shutter speeds and aperture?

Just keep remembering the following…
A Small f-stopĀ  number means more light going into the camera and greater depth of field and faster shutter speeds available.

A Big f-stop number means less light, sharper background v’s subject plus longer shutter speeds required.

 

I have some different examples below showing depth of field in action, showing how the background or foreground can be blurred or kept sharp.

Examples of Depth of Field

Small Bird at Lake Taupo, New Zealandf/1.8 – Blurred Background – bird in sharp focus and background very out of focus

Violinist at Spraoi 2011 - f/6 - performer playing violinf/5.6 – Slightly blurred backgrounds but backgrounds are identifyable

Tall Ships Fireworks 2011 - f/11 fireworks - how to take fireworks photos f/11 – Sharpness is desired and for fireworks you need pin sharp so > f/11 is required.

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