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How to get a blurred background from your dSLR's kit lens

Not getting the dreamy out-of-focus backgrounds you were hoping for from your dSLR's kit lens? Here's how to do it.

Joshua Goldman/CNET

There are plenty of good reasons to put down your smartphone or point-and-shoot and buy a digital SLR.

If, for you, it was because you drooled over food photography with a shallow depth of field or portraits where the subject is in sharp focus but the background is blurred, you may have immediately been disappointed by your shots and left wondering what you were doing wrong.

The fact is the lens that comes with most dSLRs, aka the kit lens, isn't really your best option for achieving a shallow depth of field.

Without getting into the technical details, cameras with large sensors, such as digital SLRs, are able to create more background blur than the much smaller sensors in an average point-and-shoot. However, you'll also want to use a lens with a wide maximum aperture, something the typical kit lens just doesn't have.

Nikon D7100 (with 18-105mm Lens)
The average kit lens has a small maximum aperture range -- not the best for blurred backgrounds. Sarah Tew/CNET

For example, the standard kit lens usually has a maximum aperture of f3.5 and ideally you'll what something much wider (lower f-stop number) like a lens that starts at f1.8, f2.0, or f2.8.

So, yes, if you want supersoft out-of-focus backgrounds, you're going to want to pair your dSLR with a good lens with a wide aperture. If that's not an option and all you have is the zoom lens that came with your camera, you can still cut down on distracting backgrounds and get the appearance of a shallow depth of field with these steps.

Learn your lens' minimum focus distance

If you don't understand apertures or focal lengths, that's fine because you really don't need to for this. What you should find out, though, is the focusing range for your camera. More specifically, how closely the lens can focus at its widest position (fully zoomed out) and its telephoto position (fully zoomed in).

For example, the photo at the very top of this story was taken with the Nikon f3.5-5.6 18-105mm kit lens that comes with the D7100. This lens can focus as close as 1.48 feet (0.45m). This information is usually available in the specifications section of your lens' manual or on the manufacturer's Web site. You can always just estimate it, too, through trial and error.

Zoom all the way in and get as close as possible

The longer the focal length the shallower depth of field appears. For the Nikon lens I mentioned earlier, this means zooming in to 105mm. Some dSLR kits come with two lenses in which case you'll want to use the one with the longest focal length. For example, the D7100 can be found in a kit with 18-140mm and 55-300mm lenses, so you'll want to use the 55-300mm and zoom in to 300mm.

Remember the focusing range from the earlier step? You'll need to know that for this so you know just how close you can get to your subject and have them be in focus. The closer you can get to your subject, the better off you'll be.

Joshua Goldman/CNET

Use the largest available aperture

As mentioned earlier, kit zoom lenses tend to start with a small maximum aperture and that aperture gets even smaller when zoomed in. Smaller apertures mean greater depth of field and sharper backgrounds.

While using your kit lens' maximum aperture (f5.6 in this case) won't have the same blurring capabilities as a zoom lens with an f2.8 maximum aperture, it does have some effect. Go for the widest aperture available (lowest f-stop number). For beginners, you can do this by putting your camera in Program or Aperture-priority modes, or Manual if you want complete control over aperture and shutter speed.

Put as much distance between your subject and the background as possible

Going back to the portrait up top, though the doors in the background look close, they are actually about 30 feet away from the subject. The more distance there is between your subject and the background, the more it will be out of focus.

One final note: Using a fast lens, in other words, one with a wide maximum aperture not only gives you shallow depth of field, but lets in more light, so shooting in low light is less of an issue. As you might imagine the opposite is true for smaller apertures.

When using this technique indoors, you'll need a lot of light such as from an external flash, or a slow shutter speed or high ISO setting. Outdoors in daylight, though, should be fine for most portraits and still lifes.