As this gem of an exhibition on the Upper East Side demonstrates, Edward Hopper found himself in etching.

For the first 18 years of his career, unable to support himself by painting, Hopper was obliged to work as a commercial illustrator. He worked for various New York advertising agencies, and enjoyed a short stint on the New Masses, the socialist paper whose art editor was his friend and, to some extent, mentor, John Sloan. Printmaking presented itself as a natural corollary to his day job, and in 1915 he studied the medium under the expatriate Australian Martin Lewis (who went on himself to produce Hopper-esque city scenes of haunting intensity). Hopper made around 70 etchings in total, of which the Craig F. Starr Gallery has gathered a dozen key images, including “Night Shadows” (1921) and ” Night on the El Train” (1918).

The compelling blackness of the etched plate seems to have awakened Hopper to the potency of nocturnal imagery. He loved the chiaroscuro of etching, and sought out unusually white paper to increase contrasts. There is often a sense of stark intrusion of light into dark — of the electric light cast over a lonely wanderer in “Night in the Park” (1921), for instance. “Night Shadows,” with its vertiginous view of a solitary walker on a deserted street corner, casts a long shadow behind him, while the shadow of a lamppost rudely dissects the expanse of white sidewalk that awaits him.

But lighting contrast ran deeper than some dramatic effect. In two sensational prints, “East Side Interior” (1922) and “Evening Wind” (1921), light and dark also presents a demarcation between private and public, interior and exterior. In the first image, a woman at her sewing machine in a cluttered room held in deep shadow, looks wistfully out of a big open window that illuminates her space and signals longing or hope. In the second, a naked young woman clambers into bed as her curtains billow in front of another wide-open window. Her flesh, her bedclothes, the washbasin on the night stand behind her, and the curtains are meticulously picked out, while the dense blackness of the wall behind her is heavily worked in cross-hatching. In contrast, the sky is an area of sheer, clean, untouched plate. This print went through eight states, but in each of them the expanse of sky is left white and naked.

Elevated trains were another gift to Hopper’s discovery of unexpected intrusions of privacy and open space. “House Tops” (1921) takes a long view of a carriage interior at a receding diagonal. At one end a man is absorbed in his newspaper reading, while closer to the viewer a woman turns on the bench to gaze at the cityscape rushing by out of the windows. In “Night of the El Train” the windows are pitch-black, the long seat a brilliant white. Two lovers, oblivious to the attention of fellow travelers, are lost in each other as they squeeze together to share a view from the same window. Hopper captures perfectly, in compressed gestures, the languor of the woman, with one foot rubbing on the calf of her other leg, her backside slipping off the edge of the seat as she turns to the exterior, and the anxious interest of the man, boater on his knee, whose gaze is divided between the view and his companion.

The railway suggested another theme of precarious edges, between town and country. “American Landscape” (1920), a wide cinematic vista in a plate of 7 1/2-by-12 1/2 inches, presents the idiomatic Hopper lonely house on a railway line with cattle trekking across this terrain. A glum-looking worker walks along the sidings of “The Railroad” (1922), as the track curves around toward the row of houses behind him. Directionally differentiated hatching perfectly describes the banks on either side and the housetops beyond in the glow of dusk. “The Locomotive” (1923) is a tour de force of a range of blackness as Hopper describes the shiny metal of the mammoth, looming engine making its way into the dull gloom of a tunnel.

It was thanks in part to his successes with etchings — both in terms of popularity and the iconographic discoveries that etching prompted — that he was able to go full-time as a painter in 1924, sadly letting etching go. Watercolor, the other breakthrough medium for Hopper, did not suffer the same fate. The artist noted in later years that after he took up etching — and thanks, as can be seen in this gift of an exhibition, to his success at it — “my painting seemed to crystallize.”

Until August 15 (5 E. 73rd St., between Fifth and Madison avenues, 212-570-1739).