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When it comes to backgrounds in your photos, the question is whether to blur or not to blur.
Photographers have control over whether their backgrounds are sharp and in focus or blurry and out of focus. This is done by choice of lens and aperture. The longer the lens the less sharp the background will appear. The wider the aperture more the background will look out of focus. These are basic facts known to any accomplished photographer. The question now becomes what the creative implications are for making choices like this.
Ansel Adams was known for the extreme depth of field in his photos. He did shots where everything from some rocks a few yards in front of the camera to distance mountains all appear in apparently sharp focus. He achieved this in part by using the swings and tilts of his view camera to angle the plane of focus. But Adams was also a member of Group f/64 that advocated using the smallest possible aperture to achieve the maximum depth of field possible shooting landscape photos. This created an image that seemed super-realistic but was actually an abstraction because that is not the way the human eye operates. We have to refocus our eyes from foreground to background to see everything sharply. We can't see the whole field of view, close in to infinity, simultaneously in sharp focus.
Fashion and beauty photographers have often made the opposite choice. You see a lot of fashion photos shooting at very large apertures so the model is in the foreground in sharp focus while the background is softer and mostly out of focus. This allows for the photographer to draw attention to the model and what she is wearing with no background distractions.
The way an out of background registers is called "bokeh," a Japanese term Wikipedia describes as the aesthetic quality of the blur produced in the out-of-focus parts of an image produced by a lens. Bokeh has been defined as "the way the lens renders out-of-focus points of light…the aesthetic quality of the blur produced in the out-of-focus parts of an image produced by a lens. Bokeh has been defined as "the way the lens renders out-of-focus points of light".
This has become a central aspect of recent video production. A film movie camera, like a still camera, will normally produce limited depth of field depending on focal length of lens and aperture. Until recently most video cameras did not do this but produced images that seemed totally in focus all the time. When videographers began using DSLR cameras to shoot motion, they suddenly had the ability to choose areas of focus and to employ creative techniques like highly selective focus or racking focus forward or back from one area of the frame to another. So with these and other video cameras with the same capability, filmmakers using video cameras have been able to create a much more "film like" look.
I do a lot of photos of models against dramatic landscapes, the kind of desert and mountain scenery Ansel Adams was drawn to. I like to see details in the background so I shoot with fairly small apertures. This makes the result both a good photo of the model and a good landscape photo as well. But shooting fashion, I might well to decide to open up the aperture and throw the background out of focus for a more glamorous effect.
The real point of all of this is that whether a photographer wants the background to be sharp or blurry and full of bokeh is an aesthetic choice we should all be conscious of. Simply setting the camera on automatic or program takes away some of this aesthetic control.