blur

Blur refers to the loss of sharpness in an image or scene, in which fine detail and edge definition are reduced. It can be intentional, as in artistic photography, or unintentional, arising from limitations of the imaging system or conditions of the scene.

Causes include defocus, diffraction, optical aberrations, motion of the camera or subject, and atmospheric effects such as fog or haze. Digital factors such as insufficient sampling or aggressive compression can also introduce blur. In photography, the amount and location of blur are influenced by depth of field and focus; objects outside the focused plane become defocused, producing background or foreground blur known as bokeh.

Types of blur include defocus blur, motion blur, atmospheric blur, and diffraction blur. Defocus blur results from incorrect focus, while motion blur arises from relative movement between the camera and subject. Atmospheric conditions smear fine detail at a distance, and diffraction blur is caused by the finite size of the aperture.

In imaging and computer vision, blur is modeled mathematically by a point spread function that describes how a point in the scene spreads in the image. Common blur models include Gaussian blur, box blur, and linear motion blur. Deblurring seeks to reverse blur through deconvolution and related techniques, but it is often ill-posed and limited by noise.

Perceptual effects of blur influence readability and recognition; mild blur can preserve context while reducing detail, whereas heavy blur can render a scene indistinct. Blur is used across photography, film, simulation, and computational imaging for aesthetic, depth-cue, or privacy purposes.