What does defocusing mean?
Defocusing means causing something to lose sharpness of focus or referring to the process by which that occurs. In photography, a lens can be deliberately defocused to soften an image, blur the background, or create a dreamy effect. In optics and engineering, defocusing describes adjustments that spread light away from its sharply focused point, sometimes as a deliberate way of distributing energy or reducing intensity at a focus. The word may also be used as a gerund, as in “defocusing the lens,” and as a participial adjective when describing an adjustment or effect. It is more precise than simply saying that an image is blurry: defocusing identifies a loss of optical sharpness, whether deliberate, accidental, or caused by incorrect distance, lens movement, or focus settings. The term is common in technical writing about cameras, microscopes, telescopes, lasers, and image-processing systems, though it also appears in general descriptions of photographic technique.
To cause something to lose sharpness of focus, particularly by changing the position of a lens, subject, or image plane.
"The camera was deliberately defocused to soften the scene."
Common in technical descriptions of optics, imaging, and photography; the gerund form is also used for the process.
Causing or involving a loss of optical sharpness or focus.
"The lens uses a defocusing coil to shift the focal plane."
This participial use is mainly technical and occurs in phrases such as “defocusing effect” and “defocusing correction.”
The process or state of losing sharpness or focus.
"The defocusing of the beam reduced the light concentrated at its focus."
Used chiefly in optics, imaging, and related technical contexts.
A lens can focus perfectly on one plane while turning everything in front of it or behind it into blur: defocusing is the physics of that blur.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does defocusing come from?
Defocusing was formed in English by combining the prefix de-, expressing reversal or removal, with focus. The word focus was borrowed from Latin focus, meaning “hearth” or “fire,” and came to mean the point at which converging rays meet. Related English words such as focal and confocal were subsequently developed within the same optical vocabulary.
Related word forms
How defocusing is actually used
This is chiefly a technical or semi-technical term used in optics, photography, imaging, and visual perception. In photography it may describe either accidental or deliberate loss of sharpness, while in optics it often refers to adjusting a lens or beam so that energy is no longer concentrated at the focal point.
Easily confused with defocusing
Defocus is the base verb; defocusing is its present-participle and gerund form, as in “defocusing the lens” or “the defocusing of the image.”