Astigmatism

Astigmatism is an artifact that creates stretched shapes gradually towards the edges of the image.

Note

Often confused with: it is a different phenomenon compared to what happens in human eyes with astigmatism. Which is causing lens flares.

Example image of effect

Why does it occur?

Astigmatism occurs when light rays from different directions not align at the same focal point in the lens. This causes the image to be distorted.