Blurriness

Blurriness is the lack of sharpness or clear detail in an image or scene. It occurs when light from a point in the scene does not converge to a small region on the sensor or retina, causing edges to appear soft or smeared.

Common causes include optical misfocus (the subject is not on the plane of focus), insufficient depth of field, diffraction at small apertures, optical aberrations in lenses, motion of the camera or subject during exposure, and atmospheric or medium effects that scatter light.

Blurriness can be quantified or described in objective terms using the point spread function, which describes how a point source is imaged, and metrics such as the modulation transfer function. In human vision, perception of blur depends on contrast, spatial frequency, and context.

Types of blur include out-of-focus blur, where the focal plane is wrong; motion blur, from movement; and environmental blur, due to air turbulence or haze. Blurring also accompanies very shallow depth of field, where non-focal regions are naturally soft.

Impact and use: Blurriness reduces detail and recognizability, and can hinder measurement or identification tasks. It may be undesired, as in photography, where sharpness is often valued, or intentional, as an artistic effect. In microscopy or surveillance, blur can obscure important information.

Mitigation and restoration: Reducing blur involves proper focusing, stabilizing the camera, increasing shutter speed, using appropriate aperture and optics, or using image stabilization. Digital methods such as deconvolution or sharpening can improve apparent sharpness but may fail to recover information lost to blur and can introduce artifacts, especially when noise is present.