A picture taken with the subject close to the camera. The classic close-up is about getting detail. That usually means getting right into the subject. The feeling of ‘closeness’ usually means the shot is taken from less than meter away. However, close-ups can be as close as a few inches.
The idea of a close-up is to make the viewer ‘feel’ the subject is right up close. So in some cases the picture can be further away than a Meter. To make the viewer feel the subject is close you can use different techniques. If the subject fully fills the frame and detail is clear then the size of the subject can imply closeness rather than actual distance. The use of long lenses to bring the subject into the shot optically also implies closeness. So the actual closeness may be secondary to the detail that is shown. What is important in the close-up is the feeling of immediate proximity to the subject and the expression of detail in the subject. Thus, a close-up is to some extent a subjective or artistic interpretation rather than a stated distance.
A close-up should be considered distinct from a ‘macro’ which is a close shot, but which is usually taken with a magnification factor in the lens.