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Scott's Photography
Tip - Get Blurred Backgrounds in Photos (Bokeh)

January 1, 2013
By Scott Lewis

This month I am going to tackle a simple topic for some, but a confusing topic for many. The blurred background.

Many people when they step beyond point and shoot pictures want to learn how to get a blurred background. The technical term is bokeh (Wikipedia definition).

In a nutshell what you are doing is narrowing the focus so that only one part of a picture is in focus... on purpose. This is most common with people in a field of flowers. Getting the flowers behind the person (or people) to be blurred really makes the subject pop.

This technique is done by adjusting the aperture of your camera. Most point and shoot cameras do not have an aperture adjustment. They may have a "scene" or "mode" that tries to get this effect. You'll have to check your manual.

For those of you with dSLR cameras (with removable lenses) you will be putting your camera into Aperture Priority mode. This will be represented by an A on your dial (or Av). When in Aperture priority you will use a scroll wheel to adjust the aperture.

For this tip we are going to keep this as simple as possible. To get a blurred background you want to use the lowest aperture number you can. Most dSLR cameras that have kit lenses will go down to f/3.5 or f/4.5. This will give you some blurring, but not a lot. If you have a non-zoom lens it will usually go lower, usually to around f/1.4 or f/1.8 or f/2.0.

To make this easy... remember it this way... the lower the number... the less will be in focus. The larger the number... the more will be in focus. Small number... small focus, big number... big focus.

That is really all there is to it. You have to experiment to see how low a number you want to use. I suggest taking pictures of still objects to practice. You do have a digital camera, right? Then practice is cheap. Put two objects on your kitchen table. One near the edge of the table you are standing at, and another at the opposite end. Take a picture at each aperture setting your camera has. Then upload the photos to your computer and look at the results.

Here are a set of pictures I took recently. The main camera in this picture is the only thing in focus. The rest is determined by the aperture.

f/22 f/16 f/11 f/8 f/5.6
   
f/4 f/2.8 f/2.2 f/1.8

In the above pictures you are only starting to get a noticeable blur at f/8. At f/5.6 it is nice enough to look like it was on purpose. This might be the limit of some kit and zoom lenses. With a good prime lens (non-zoom lens) you can get significant blur as shown in the bottom row of pictures.

Once you know how much range your camera and lens have, and how much of the effect you want... you can start taking pictures with an eye toward getting the good bokeh.

I took this pictures of a bird at f/1.8 with a 28mm lens. I was stunned that the bird let me get this close without moving.

I don't want to complicate this too much for beginners... but to get a good amount of blur usually requires a lot of light. So outdoors is the place to practice the most.

The Technical Stuff

For those that are really interested... here is the technical information. The aperture of a camera is changed in f-stops. Each f-stop represents a doubling of light.

The main f-stops are:

1.4, 2.0, 2.8, 4, 5.6, 8, 11, 16, 22

Modern digital cameras & lenses can have many more aperture settings than these. But these represent the light properly.

As we said, the amount of light from one f-stop to another is double. The lower the f-stop the more light enters the camera. This is because the lower the number, the larger the aperture, or opening, in the lens. For instance, f/1.4 lets in twice as much light as f/2.0, which lets in twice as much as f/2.8... and so on through the f-stops listed above.

If your camera can move to f-stops between those listed above those are 1/2 or 1/3 f-stop changes... and the camera is also adjusting the shutter speed accordingly (in smaller amounts than full stops of light).

When using the aperture setting to blur the background we are increasing the quantity of light into the camera... but we reduce the time the lens stays open. The end result is the same amount of light... just in a different way. Increasing the quantity of light -- by using a lower f-stop (larger lens opening) we then decrease the time the light is available to the camera to get everything in focus. So... the background and foreground become blurred, and just what the camera is focused on remains clear.

Advanced Tip

When shooting in ultra wide aperture (1.x) use the spot focus on your camera.

When I started out I used to like to focus on a subject (press the shutter half way down) then move the camera a little to the left or right so the subject is off center for a better composition. I would then take the picture. However, at f/1.4 and f/1.8 the subject would frequently be slightly out of focus.

What is happening is that when you are holding the focus locked, by holding down the shutter half way, you are changing the distance of the sensor in the camera to the subject when you recompose. In very wide apertures this is enough to throw your subject slightly out of focus.

To correct for this set your camera to focus using one of the "spots" to the left or right of the viewing area and compose the shot with the subject off center... and in focus.

Conclusion

I hope this was useful. I am still learning how to use a camera, and as I learn more techniques I hope to share them here.

Now get out there at take some pictures.

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