True wide-angle distortion describes the way in which three-dimensional objects near the edges of the field of view appear ‘stretched’ out of shape because of the angle of view of the lens: a round ball is distorted into an ellipse, and a human head can look quite unpleasant. It is not so much a defect as an inherent property of extreme wide-angle lenses: it cannot be ‘designed out’ and has been used to powerful creative effect, most notably in the nudes of Bill Brandt. It should not be confused with another kind of distortion sometimes seen in cheaper retrofocus lenses, namely, ‘barrel distortion’ or the bowing outwards of straight lines near the edge of the image area.
— Roger W. Hicks
