Telephoto lenses have the opposite problem, referred to as pincushion distortion. This gives lines a circular, barrel-like shape. With this distortion, straight lines will remain straight towards the center but curve out at the edges of the image. The type of distortion caused by that extreme curve of a wide-angle lens is called barrel distortion. Magnify a line at the edges and not in the center, and that line appears to curve at the edges.
That difference means the objects at the edge of the frame aren’t enlarged as much as the objects in the center. But the curve also means the objects at the edge of the image are a different distance from the lens than those at the center. The curved shape allows the lens to capture a wide view of the scene. Glass from wide-angle lenses have much more spherical glass than a telephoto lens. To capture a wide field of view, that glass needs to have a more extreme curve to project onto the camera sensor. This action projects an image onto the camera sensor or a piece of film.
The glass lens (or in most cases, a series of glass lenses inside a single camera lens) works by bending the light. The best way to understand lens distortion is to first grasp the gist of how lenses actually work.
Also requires smart device to be using operating system iOS 8.4 (or later) or Android 5.How Lenses Work And Why Distortion Happens
Varies depending on the subject, memory card brand and capacity, image recording quality, ISO speed, drive mode, Picture Style, Custom functions etc.