Lichtenstein took the image for Girl with Ball straight from an advertisement, for a hotel in the Pocono Mountains. In pirating the image, however, he transformed it, submitting the ad's photograph to the techniques of the comic-strip artist and printer—and transforming those techniques, too, into a painter's versions of them. The resulting simplifications intensify the artifice of the picture, curdling its careful dream of fun in the sun. The girl's rounded mouth is more doll-like than female; any sex appeal she had has become as plastic as her beach ball.
In choosing the banal subject matter of paintings like Girl with Ball, Lichtenstein challenged the aesthetic orthodoxy of the time, still permeated by the spiritual and conceptual ambitions of Abstract Expressionism. The moral seriousness of art, and art's longevity, seemed foreign to this cheap, transient ad from the consumer marketplace, a sector of roiling turnover. Startling though the image was as an artwork, in fact, as advertising it was already old-fashioned—so that Lichtenstein's painting admits of a certain nostalgia. His simulation of printing similarly robs the technology of the polish it had already achieved: overstating the dots of the Benday process, and limiting his palette to primary colors, he exaggerates the limitations of mechanical reproduction, which becomes as much the subject of the painting as the girl herself.
from The Museum of Modern Art, MoMA Highlights, New York: The Museum of Modern Art, revised 2004, originally published 1999, p. 238