What causes image blur

Camera shake: Photographer's movement while the shutter is open affects stable camera position, resulting in overlapping of the entire image. This phenomenon occurs more readily at slower shutter speeds, such as in dark situations, or when a photographer uses a lens with a long focal length. Usually, it can be prevented by using a tripod. When you don't have one, you can minimize image blur to some extent by steadying the camera or your own body against a railing or wall.

  • Without camera shake

  • With camera shake

How is it different from subject movement or defocusing?

Subject movement:

Image blur can result from the subject moving while the shutter is open. Such movement results in the subject only being blurred. To some extent, this kind of image blur can be prevented by setting your camera to a faster shutter speed. In some cases, the photographer may want to make use of intentional blurring to emphasize the subject's movement.

  • Without subject movement

  • With subject movement

Defocusing:

This kind of image blur is the result of focusing unintentionally on an object different from the photographer's intended subject. Such defocusing results in the subject being obscured. Depending on circumstances, the entire image may be blurred.

  • Correctly focused

  • Defocused