Lens distortion is a common characteristic of all types of camera lenses to varying extents. There are several effective techniques you can employ to minimize its impact and achieve optimal image quality. These include careful lens selection, proper shooting techniques, and post-processing adjustments.

Understanding lens distortion can actually help you improve the quality of your images and give you more control over the final result.

Pincushiondistortionphotography

In the sign convention used here, the value of R1 will be positive if the first lens surface is convex, and negative if it is concave. The value of R2 is negative if the second surface is convex, and positive if concave. Sign conventions vary between different authors, which results in different forms of these equations depending on the convention used.

Lens distortion, at its core, is a deviation from the 'ideal' image – typically, one that is geometrically perfect. Before we can analyze the intricate aspects of managing lens distortion, it's key to establish a clear understanding of what it actually is.

Lens distortion can significantly affect your photography, particularly if you're shooting architecture or any subject with straight lines. The curving effect of barrel or pincushion distortion can make buildings appear to lean or warp, which can be visually distracting.

Remember, in photography, knowing how to manage imperfections can often be as important as seeking perfection. Embrace the artistic possibilities that lens distortion offers, and use it as another tool to create compelling images. The world of photography is as much about control as it is about creativity.

There are three primary types of lens distortions. Understanding and recognizing these distortions is essential for photographers and videographers. The three types of lens distortion are barrel distortion, pincushion distortion, and mustache distortion.

Due to the popularity of the 35 mm standard, camera–lens combinations are often described in terms of their 35 mm-equivalent focal length, that is, the focal length of a lens that would have the same angle of view, or field of view, if used on a full-frame 35 mm camera. Use of a 35 mm-equivalent focal length is particularly common with digital cameras, which often use sensors smaller than 35 mm film, and so require correspondingly shorter focal lengths to achieve a given angle of view, by a factor known as the crop factor.

Kyle DeGuzman graduated from San Diego State University with a Bachelor of Science in Television, Film, & New Media. He currently resides in Denver, Colorado spending his time writing, filmmaking, and traveling.

The science behind lens distortion lies in how a lens works and the path of light as it interacts with the lens. When light enters the lens, it undergoes a process called refraction, where its direction changes due to the change in medium.

Mustache distortion, also known as complex distortion, is a combination of barrel and pincushion distortion. The image appears to warp in a wavy pattern, with lines curving outward near the center and inward at the edges.

For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci (or focal points) of the lens. For a converging lens (for example a convex lens), the focal length is positive and is the distance at which a beam of collimated light will be focused to a single spot. For a diverging lens (for example a concave lens), the focal length is negative and is the distance to the point from which a collimated beam appears to be diverging after passing through the lens.

Photography is more than just clicking the shutter. It’s about truly understanding your camera and the lenses you use as tools. One aspect that often gets overlooked is lens distortion. It’s a common occurrence, yet many photographers are unaware of its impact on their photos.

A lens with a focal length about equal to the diagonal size of the film or sensor format is known as a normal lens; its angle of view is similar to the angle subtended by a large-enough print viewed at a typical viewing distance of the print diagonal, which therefore yields a normal perspective when viewing the print;[9] this angle of view is about 53 degrees diagonally. For full-frame 35 mm-format cameras, the diagonal is 43 mm and a typical "normal" lens has a 50 mm focal length. A lens with a focal length shorter than normal is often referred to as a wide-angle lens (typically 35 mm and less, for 35 mm-format cameras), while a lens significantly longer than normal may be referred to as a telephoto lens (typically 85 mm and more, for 35 mm-format cameras). Technically, long focal length lenses are only "telephoto" if the focal length is longer than the physical length of the lens, but the term is often used to describe any long focal length lens.

For an optical system in a medium other than air or vacuum, the front and rear focal lengths are equal to the EFL times the refractive index of the medium in front of or behind the lens (n1 and n2 in the diagram above). The term "focal length" by itself is ambiguous in this case. The historical usage was to define the "focal length" as the EFL times the index of refraction of the medium.[2][4] For a system with different media on both sides, such as the human eye, the front and rear focal lengths are not equal to one another, and convention may dictate which one is called "the focal length" of the system. Some modern authors avoid this ambiguity by instead defining "focal length" to be a synonym for EFL.[1]

The distinction between front/rear focal length and EFL is important for studying the human eye. The eye can be represented by an equivalent thin lens at an air/fluid boundary with front and rear focal lengths equal to those of the eye, or it can be represented by a different equivalent thin lens that is totally in air, with focal length equal to the eye's EFL.

What is barrel distortioncorrection

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Different focal lengths exhibit different levels of distortion. Wide-angle lenses tend to have more distortion, so for subjects with straight lines, consider using a telephoto or standard lens.

What is barrel distortionin glasses

1 f = ( n − 1 ) ( 1 R 1 − 1 R 2 + ( n − 1 ) d n R 1 R 2 ) , {\displaystyle {\frac {1}{f}}=(n-1)\left({\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}+{\frac {(n-1)d}{nR_{1}R_{2}}}\right),} where n is the refractive index of the lens medium. The quantity ⁠1/f⁠ is also known as the optical power of the lens.

Many photo editing software programs, like Adobe Lightroom and Photoshop, have lens correction tools that can automatically correct distortion based on the lens used.

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For a thick lens (one which has a non-negligible thickness), or an imaging system consisting of several lenses or mirrors (e.g. a photographic lens or a telescope), there are several related concepts that are referred to as focal lengths:

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For an optical system in air the effective focal length, front focal length, and rear focal length are all the same and may be called simply "focal length".

While lens distortion can be a unique quality you’d like to keep within your photography, it can also be one that you want to know how to mitigate as much as possible.

When a photographic lens is set to "infinity", its rear principal plane is separated from the sensor or film, which is then situated at the focal plane, by the lens's focal length. Objects far away from the camera then produce sharp images on the sensor or film, which is also at the image plane.

Mustachedistortion

Barrel distortionexamples

When a lens is used to form an image of some object, the distance from the object to the lens u, the distance from the lens to the image v, and the focal length f are related by

However, due to the inherent imperfections in lens design and the curved nature of the lens, light rays often converge at different points, causing image distortion. These distortions can manifest as barrel distortion, where straight lines appear curved outward, or pincushion distortion, where straight lines appear curved inward.

Focal length (f) and field of view (FOV) of a lens are inversely proportional. For a standard rectilinear lens, F O V = 2 arctan ⁡ ( x 2 f ) {\textstyle \mathrm {FOV} =2\arctan {\left({x \over 2f}\right)}} , where x is the width of the film or imaging sensor.

Composition is also a factor. Position your subject in the center of the frame where distortion is usually least noticeable. For example, in portrait photography, frame your subject in the center of the frame for the least amount of lens distortion on your subject's face.

The focal length of a lens determines the magnification at which it images distant objects. It is equal to the distance between the image plane and a pinhole that images distant objects the same size as the lens in question. For rectilinear lenses (that is, with no image distortion), the imaging of distant objects is well modelled as a pinhole camera model.[7] This model leads to the simple geometric model that photographers use for computing the angle of view of a camera; in this case, the angle of view depends only on the ratio of focal length to film size. In general, the angle of view depends also on the distortion.[8]

Ideally, all the light rays should converge at a single point on the sensor, resulting in a sharp and undistorted image. To understand this visually, check out our breakdown on types of camera lenses.

To render closer objects in sharp focus, the lens must be adjusted to increase the distance between the rear principal plane and the film, to put the film at the image plane. The focal length f, the distance from the front principal plane to the object to photograph s1, and the distance from the rear principal plane to the image plane s2 are then related by:

What is barrel distortionin photography

Lens distortion is an inherent characteristic of camera lenses that can significantly affect your photography. While it can be detrimental in certain contexts, such as architectural photography, it can also add a unique perspective to images when used intentionally.

For a spherically-curved mirror in air, the magnitude of the focal length is equal to the radius of curvature of the mirror divided by two. The focal length is positive for a concave mirror, and negative for a convex mirror. In the sign convention used in optical design, a concave mirror has negative radius of curvature, so

The focal length of a thin convex lens can be easily measured by using it to form an image of a distant light source on a screen. The lens is moved until a sharp image is formed on the screen. In this case ⁠1/u⁠ is negligible, and the focal length is then given by

As s1 is decreased, s2 must be increased. For example, consider a normal lens for a 35 mm camera with a focal length of f = 50 mm. To focus a distant object (s1 ≈ ∞), the rear principal plane of the lens must be located a distance s2 = 50 mm from the film plane, so that it is at the location of the image plane. To focus an object 1 m away (s1 = 1,000 mm), the lens must be moved 2.6 mm farther away from the film plane, to s2 = 52.6 mm.

The optical power of a lens or curved mirror is a physical quantity equal to the reciprocal of the focal length, expressed in metres. A dioptre is its unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dioptre = 1 m−1. For example, a 2-dioptre lens brings parallel rays of light to focus at 1⁄2 metre. A flat window has an optical power of zero dioptres, as it does not cause light to converge or diverge.[10]

Lens distortion, in simple terms, is a deviation from the perfect image caused by the optical design of a lens. This deviation results in the image being distorted in a way that differs from the actual scene. The amount and type of distortion depend on the lens design, with wide-angle lenses typically exhibiting more distortion than telephoto lenses. But this depends on the manufacturer and when it was made.

Now that we've explored lens distortion, its types, and how to mitigate its effects, it's time to look deeper into the world of lenses. In our next article, we break down how the camera lens works with light and capturing images.

For the case of a lens of thickness d in air (n1 = n2 = 1), and surfaces with radii of curvature R1 and R2, the effective focal length f is given by the Lensmaker's equation:[5]

However, not all effects of lens distortion are negative. In some cases, it can add a unique perspective to your photos, particularly in wide-angle landscape photos or street photography. The bulging effect of barrel distortion can emphasize scale and depth, making your images more dynamic and engaging.

The corresponding front focal distance is:[6] FFD = f ( 1 + ( n − 1 ) d n R 2 ) , {\displaystyle {\mbox{FFD}}=f\left(1+{\frac {(n-1)d}{nR_{2}}}\right),} and the back focal distance: BFD = f ( 1 − ( n − 1 ) d n R 1 ) . {\displaystyle {\mbox{BFD}}=f\left(1-{\frac {(n-1)d}{nR_{1}}}\right).}

The main benefit of using optical power rather than focal length is that the thin lens formula has the object distance, image distance, and focal length all as reciprocals. Additionally, when relatively thin lenses are placed close together their powers approximately add. Thus, a thin 2.0-dioptre lens placed close to a thin 0.5-dioptre lens yields almost the same focal length as a single 2.5-dioptre lens.

Camera lens focal lengths are usually specified in millimetres (mm), but some older lenses are marked in centimetres (cm) or inches.

The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light. A system with a shorter focal length bends the rays more sharply, bringing them to a focus in a shorter distance or diverging them more quickly. For the special case of a thin lens in air, a positive focal length is the distance over which initially collimated (parallel) rays are brought to a focus, or alternatively a negative focal length indicates how far in front of the lens a point source must be located to form a collimated beam. For more general optical systems, the focal length has no intuitive meaning; it is simply the inverse of the system's optical power.

Barrel distortion is common in wide-angle lenses and is characterized by the image appearing to bulge outwards from the center. In barrel distortion, straight lines near the edges of the frame appear curved outward.

Pincushion distortion is often seen in telephoto lenses. Here, the image appears pinched at the center, and straight lines near the edges of the frame curve inward.

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In most photography and all telescopy, where the subject is essentially infinitely far away, longer focal length (lower optical power) leads to higher magnification and a narrower angle of view; conversely, shorter focal length or higher optical power is associated with lower magnification and a wider angle of view. On the other hand, in applications such as microscopy in which magnification is achieved by bringing the object close to the lens, a shorter focal length (higher optical power) leads to higher magnification because the subject can be brought closer to the center of projection.

Determining the focal length of a concave lens is somewhat more difficult. The focal length of such a lens is defined as the point at which the spreading beams of light meet when they are extended backwards. No image is formed during such a test, and the focal length must be determined by passing light (for example, the light of a laser beam) through the lens, examining how much that light becomes dispersed/ bent, and following the beam of light backwards to the lens's focal point.