Distortion

Aberration that the image is distorted and the shape of the object is deformed on the screen is called distortion.
Distortion aberration that seems to bulge from the center to the outside barrel distortion (negative distortion aberration)The distortion that appears to bulge from the outside to the center is called pincushion distortion (positive distortion).
The calculation method is different for distortion and TV distortion.
TV distortion is the difference in height between the corners and the center edge of the square image expressed as a percentage. This describes the apparent straightness of lines which appear at the edge.
Distortion (D) = ((ý-ÿ) / ÿ) x 100
TV distortion (TV.D) = (△h / 2h) x 100″