Why Do You Get Vignetting?

Vignetting is even more apparent when the photo is taken with a wide aperture because it is caused when the front part of the lens blocks the camera from receiving light. Vignetting results in a progressive loss of brightness as the distance from the center of the image increases.

What causes vignetting?

Mechanical or physical vignetting is caused by an physical obstruction preventing light within the lens' field of view from reaching the camera's image sensor. ... This effect is often noticed in images taken with wide angle and wide aperture lenses used with wide open apertures.

How do I get rid of vignetting?

To remove vignetting in Lightroom all you need to do is head into the Develop module and under the Lens Corrections panel select the Enable Profile Corrections box. Once this box is checked it will remove the vignette based on a profile based on the camera or lens you used.