Nikon lens with a lot blur background?
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Do you know of any new Nikon lenses with a lot of background blur?
for D7000 or D5100
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Http://www.amazon.com/Nikon-50mm-Nikkor-Digital-Cameras/dp/B00005LEN4/
That one, for example.
You need to be looking for a lens with an f-stop number between 1.4 and 2.8. But those lenses are usually quite expensive.
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Any nikon lens can provide a shallow depth of field (blurry background) do some research into how depth of field works and you will be able to achieve it with any lens.
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Read up about depth of field and how a shallow depth of field is achieved.
Lenses capable of a wide aperture (f2.8 or wider) or telephoto lenses (200mm & above) should be able to provide you with what you want.
Of course a fast telephoto lens has the best of both worlds - but is extremely expensive! For example, the Nikon 70-200mm f2.8 is around £1200. The Sigma 200-500mm is about £12, 000!
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The lower the f/number of the lens, the easier to blur background.
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Get close to your subject; background in a distance; use the widest aperture possible = most blurry background.
Examples: http://www.althephoto.com/concepts/dof.php
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The Nikon AF-S 50mm f1.8. The older AF-D model won't autofocus with the D5100, although it will with the D7000. The newer AF-S model will also have better sharpness wide open than the older one. The AF-D needs to be stopped down to about f4.5 or more to be sharp.