What technique is effectively used for emphasizing a subject by blurring the background?

The technique of emphasizing a subject by blurring the background is referred to as selective depth of field. This method allows the viewer to focus on a specific subject while creating a soft blur in the background, which helps eliminate distractions and draws attention to the main element in the frame. Selective depth of field is commonly achieved through the use of a wide aperture, which reduces the depth of field and produces that desired bokeh effect in the out-of-focus areas.

In contrast, other techniques listed serve different purposes. Pull focus is about shifting the focus from one subject to another within the same shot, rather than emphasizing a single subject against a blurred background. Great depth of field maintains focus on both the subject and the background, which does not create the same level of emphasis on the subject as selective depth of field does. A close-up shot involves framing the subject tightly but does not specifically address the background blur needed for emphasis. Thus, selective depth of field is the most effective technique in this context for highlighting a subject by blurring the surrounding area.