Barrel distortion is a term commonly used in photography to describe a type of lens aberration where straight lines near the edges of an image appear curved, resembling the shape of a barrel. The spelling of "barrel" is represented in IPA phonetic transcription as /ˈbærəl/. Meanwhile, "distortion" is spelled as /dɪˈstɔːʃən/. Together, these two words make up a technical term that can help photographers identify and correct issues with their equipment or technique.
Barrel distortion is an optical aberration that occurs in a lens resulting in a distortion effect where straight lines appear to curve outward towards the edges of the image, resembling the shape of a barrel or an exaggerated convex lens. This type of distortion is characterized by the elongation or bulging of the center section of the image, causing a magnification effect towards the periphery.
Barrel distortion is most commonly observed in wide-angle lenses, especially those with a short focal length. It is caused by the way the lens bends light as it passes through elements of different refractive indices. The curvature of the lens causes light rays to be refracted more in the center, resulting in the center of the image being captured with a shorter effective focal length compared to the outer edges.
This distortion can have significant impact on the accuracy and quality of images, particularly when the scene contains predominantly straight lines or geometric patterns. It can lead to objects appearing stretched or bulged, with straight lines near the edges appearing to be bowed outward. Barrel distortion can be corrected to a certain extent using software or post-processing techniques, but complete elimination of the distortion may not always be achievable.
In summary, barrel distortion refers to the optical aberration produced by a lens, causing straight lines to curve outward towards the edges, resembling the shape of a barrel. It commonly occurs in wide-angle lenses and can affect the accuracy and quality of images, particularly those with prominent straight lines or patterns.
The word "barrel distortion" is composed of two parts: "barrel" and "distortion".
- "Barrel" refers to a cylindrical container often used for storing and transporting liquids, typically made of wooden or metal staves bound together with hoops. It is derived from the Old French word "baril" and ultimately from the Gaulish word "barilum", meaning a vessel or container.
- "Distortion" is derived from the Latin word "distorsio", which means a twisting or turning aside. It is further related to the Latin verb "distorquere", meaning to distort or contort.
In the context of optics and photography, "barrel distortion" refers to a form of lens distortion where straight lines near the edges of an image curve outward, resembling the shape of a barrel or a fisheye lens.