This is usually caused by wide-angle lens distortion, especially a mix of perspective distortion and barrel distortion.

With a wide-angle lens, objects near the edges of the frame can appear stretched or warped because the lens is capturing a very wide field of view. Faces and bodies near the corners often look unnatural, which is why wide-angle lenses are usually not ideal for portraits.

Barrel distortion is when straight lines bow outward, and perspective distortion is the exaggerated look you get when subjects are close to the lens. Together, they can make people at the edges look wider or stretched.

How to avoid it:

• Don’t place people close to the corners of the frame.
• Step back and use a longer focal length if possible.
• Avoid very wide-angle lenses for portraits.
• Use a higher-quality lens, which may reduce barrel distortion.

Wide-angle distortion isn’t always a defect—it can also be used creatively, and it’s often useful for interiors or dramatic effects.