Blurs

Blur refers to a loss of image sharpness in which fine details become indistinct as light from a scene spreads over neighboring image elements. It can be caused by physical processes in the optical path, the scene itself, or by digital processing. In optics, blur is often described by a point spread function, which describes how a single point of light is recorded as a spread-out region on the sensor, reducing local contrast and perceived detail.

Causes and types include optical blur from defocus or lens aberrations; motion blur from camera or subject movement during exposure; diffraction blur that occurs at small apertures due to the wave nature of light; and atmospheric or haze-related blur from particles in the air. Digital blur is produced by applying a convolution with a blur kernel, with common examples such as Gaussian blur or box blur. Out-of-focus light sources can form soft circles known as bokeh, whose appearance is influenced by the lens aperture shape and design.

Measurement and processing approaches use concepts such as the point spread function (PSF) and the modulation transfer function (MTF) to characterize blur. Deblurring, including blind deconvolution, aims to reverse blur by estimating the PSF and restoring sharpness, though perfect restoration is often unattainable due to information loss and noise.

Applications range from artistic control of depth of field and motion portrayal in photography and film to privacy protection in imagery and challenges in computer vision systems. Understanding blur is central to camera design, image processing, and visual perception.