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How can I take the photo with the focus on the main object and blurred background using the Nikon D5100? What kind of mode and settings I should use? Thanks.

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marked as duplicate by mattdm, MikeW, Stan Rogers, whuber, Michael Clark Apr 15 '13 at 5:17

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
What lens(es) do you have? –  ElendilTheTall Apr 14 '13 at 20:27

2 Answers 2

up vote 5 down vote accepted

This is called "shallow depth of field", there are 3 factor (that you control) that affect depth of field:

  1. Distance to subject - as you get closer less will be in focus, also, you will get more background blur if the background is far away

  2. Focal length - longer focal length = less in focus

  3. Aperture - this is the easiest to use because it's a setting you dial into your camera but it's the "weakest" factor of the 3, to get less in focus use a bigger aperture (smaller F number)

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it's worth pointing out that if they are looking for a particular composition, the distance to subject and focal length are linked which makes aperture a much stronger factor relative to the ratio between the other two (depending on shot conditions at least). For example, on a full frame at f/4, 10 feet and 50mm the DoF is 2.94 feet. Alter it to be 100mm and 20 feet (same shot width) and the DoF is only 2.89 feet. .5 feet for a doubling change. Dropping to f/2.8 (50mm and 10ft) gives 2.06 feet or a change of .88 feet. –  AJ Henderson Apr 14 '13 at 20:19
    
@AJHenderson - someone following your advice with his brand new APS-C DSLR and kit lens is going to try to shoot everything in 18mm f/3.5, the hyperfocal distance will be just below 16 feet and getting significant background blur will be nearly impossible (possibly unless the background is a mountain in the distance), at the telephoto end with 55mm at f/5.6 the hyperfocal distance is 92.5 feet and any typical shooting distance (for friends and family, not animals in a safari) will give you a DOF of less than 5 feet (people who own f/2.8 lenses probably don't need to ask this question) –  Nir Apr 15 '13 at 21:16
    
The best balancing point is going to depend on how far out they can stay wide-open. Say for example they are able to make it to 28mm on f/3.6, at 10 feet (on a crop sensor), they would have a dof of 5.6 feet. Going to 55mm and f/5.6 with a similar composition (20 feet to subject), the dof is going to be 9 feet. Not quite double, so they may very well still be better up close with it more open. –  AJ Henderson Apr 15 '13 at 23:29
    
Oh wait, maybe I see what you are saying now. You're looking at the fact that the hyper focal distance will be reached sooner. I suppose that would be true if the background is actually far enough away. In my example, the background would need to be at least 35 feet behind the subject or the shorter configuration would still give more blur if my understanding is correct. –  AJ Henderson Apr 15 '13 at 23:50
    
@AJHenderson - you didn't read the question correctly, it wasn't "how to blur the background more for the same composition" it's "I got this new camera that should be able to blur the background and I can't do it", the asker has a D5100 - a DX camera and he probably has the 18-55mm f/3.5-5.6G VR kit lens that only reaches max aperture at 18-ish mm - now, you can't get nice blurred background at 18mm, this just isn't going to work in any common shooting scenario, however, at 55mm f/5.6 just about any headshot will show some background blur –  Nir Apr 16 '13 at 20:30

The effect you are looking for is called Bokeh and it is a result of using a narrow depth of field. To achieve the look, you need to decrease your depth of field to put the background out of focus. You can minimize the depth of field by using the widest open aperture possible and if that does not accomplish what you are looking for sufficiently, then you can try to increase the focal length (zoom in) and shoot from further away. It's worth noting however that on many telephoto lenses, the aperture will actually stop down as you get in to longer focal lengths, so the best result will probably be on the longest focal length you can reach while maintaining a wide open aperture.

It is worth noting that while technically decreasing the distance to the subject or increasing the focal length has a larger change to the DoF than aperture, if you want to be able to maintain a consistent shot composition, getting closer to a subject will requires a smaller focal length and vice versa, so the change in depth of field is reduced some for those. Generally, the focal length will make the depth of field shorter than the distance will, so being far away with a long focal length will give you the smallest depth of field for a particular shot if aperture isn't sufficient.

You can use this blur calculator to figure out the best way to maximize your background blur.

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Bokeh refers to the quality of the out-of-focus areas of a photograph. Using it to refer to an "effect" or style of shooting is sloppy usage, IMO. –  coneslayer Apr 14 '13 at 19:14
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@Coneslayer - the term's definition is not so clear cut. Wikipedia has several references which support the use as both the visual look as well as the quality of the look. If you notice, after mentioning that it is bokeh, I explain it all as being achieved through a shallow depth of field. Thanks for the comment though, I was unaware of it also referring to the quality. –  AJ Henderson Apr 14 '13 at 19:52
    
@coneslayer - Check this answer to another question. Quote: "To really show this effect, you can use a technique to create "shaped bokeh". In doing so, you can even make the areas show as well recognized shapes, like Christmas trees or stars." –  Esa Paulasto Apr 14 '13 at 21:43
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“English doesn't borrow from other languages. English follows other languages down dark alleys, knocks them over and goes through their pockets for loose grammar.” (James Nicoll) When I first came across the terms boke(h) and nisen-boke(h) (outlined bokeh), they were about the shape and quality of the out-of-focus highlights in an image, and the terms were distinctly Japanese borrowings and ideas. Well, we're not giving it back, and we've decided that since we own it now, we can do what we like with it. It'll make reading stuff from the '80s and '90s harder, but it's changed for good. –  user2719 Apr 15 '13 at 1:12
    
At the same time new editions of dictionaries include definitions of words that are tied to their etymological origins they also include new meanings derived from contemporary usage. –  Michael Clark Apr 15 '13 at 3:12

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