Focus

(1) The term “focus” refers to the degree of sharpness or distinctness of a particular area in an image (such as a person, object, etc.). If something is “in focus”, it appears sharp and clear. In contrast, if an object or an area is “out of focus”, it appears blurred and indistinct. This area is also referred to as bokeh. Technical terms related to “focus” include deep focus, shallow focus (very common in close-ups), soft focus, and rack focus.

(2) Focusing is the act of adjusting a lens system in such a way as to achieve a sharp image along the focal plane.