Just out of art school, growing up in the New York art world in the late 1940s, you took the Hopper paintings down at the Whitney Museum on 8th Street with a grain of salt. Their white New England spareness, their stony wastes of city houses, their girdered grey bridges, the inhibited people sitting on beds in lonely rooms or leaning in dark brown interiors, the no-nonsense contrasts between harsh eastern seaboard light and thick indoor shade, were plainspoken, bold but conventional Americana. Yet sometimes you were arrested by an odd undertow which made you retrace your steps to take a second look and wonder. But Hopper and his pals were pass