The simple gas street lamp stands as a beacon of modernity — simultaneously clean, graceful and stalwart.

Seen through French photographer Charles Marville’s lens in “Hôtel de la Marine” it also serves as a geometric bisector, a meditation on the alienation of modernity and as the signature emblem of the new Paris as “City of Light.”

Marville’s albumen print was commissioned in the 1870s as part of an effort to document the 96 prototypes of the more than 20,000 gas lamps that Napoleon III’s urban planner, Baron Haussmann, installed in Paris as part of his mid-19th century transformation of the city’s medieval core. It was a heady time. Cramped streets and houses in the Latin Quarter and Îsle de la Cité were demolished to make room for the construction of spacious boulevards, public parks and modernized sewage. In 1860, for instance, the city nearly doubled in size, expanding to its current 20 arrondissements and

reshaping itself into the fashionable tourist’s delight it has largely remained to this day.

Aspects of this metamorphosis, and its enduring aesthetic impact, unfold in “Paris in Transition: Photographs from the National Gallery of Art,” a new exhibit of 61 images opening Sunday in the National Gallery’s West Building. The show, which takes the viewer on a leisurely walk through Paris and its environs — from quiet scenes of the Seine River to construction sites to music halls to tourist landmarks — is alternately nostalgic, cosmopolitan, ironic, reflective, documentary and painterly. The old Paris of squalid, narrow byways and horse-drawn carts, which Marville also was commissioned to record, gives way to a more modern and often more commercial milieu. And photography (whose birth was fittingly announced in Paris in 1839) was the perfect medium to document the changes and growth of the city from the 1840s to the 1930s (the period covered in the show).

Charles Soulier’s “Panorama of Paris, Near the Pont des Arts” (1862), for instance, juxtaposes the towers of Notre Dame with a less exulted building in the foreground that boasts an advertisement for a dentist at five francs per visit. Below, a triangle of the Seine has been blocked off for a swimming school.

Several photographs document the flurry of building that marked the Haussmann changes, from the construction of the magnificent Opéra Garnier in the late 1860s and 1870s to the new wing that was added to the Louvre, as well as other less-exulted, but perhaps more practical, projects.

In the 1870s, for instance, Hippolyte-August Collard snapped workers atop the construction site of the massive reservoir at Montrouge (which drastically improved the cleanliness of Paris’ bacteria-ridden water). But his work wasn’t merely documentary; in another picture, Collard transformed with the click of his camera a sweeping Romanesque aqueduct (built under Haussmann’s direction) spanning an otherwise open field into an aesthetic, almost mythical, wonder.

In the late 19th and early 20th century, Eugène Atget — one of the most famous and prolific photographers to tackle Paris (he shot some 10,000 photographs with a simple box-style camera) — imbued his pictures with an elegiac, yet forward looking, elegance, with nods to old and new Paris, appropriate for an artist whose market consisted mainly of conservators, designers and city officials.

He turned his lens on anonymous store windows, memorializing a quartet of mannequins in middle-brow attire. Other times, it’s the storefronts of ancient Paris, such as the wine shop “A la Grappe d’Or, 4 place d’Aligre,” where he captures the reflection of a streetlight and tiny passersby (which almost look like wine bottles) in the door’s glass window, creating a picture within a picture. And Atget’s poetic views of the city’s architectural elements, such as his “Notre Dame” seen from across the Seine and obscured by the cobweb-like branches of a tree, are some of the understated delights of the show.

In contrast, Alfred Stieglitz’s “A Wet Day on the Boulevard, Paris” (1894) is more unabashedly new Paris, with its well-heeled Parisians strolling through the heavily trafficked intersection of the Boulevard des Italiens and the Rue Scribe amid signs advertising such bourgeoisie yens as perfume and lawn tennis. Stieglitz, who was among the foreign artists who flocked to the city during the belle époque, developed the carbon print on watercolor paper, adding an element of texture (almost shimmer) to the rainy scene he depicts.

The exhibit also includes several of the Hungarian-born Brassaï’s explorations of Paris after dark, some of which ended up in his 1933 book “Paris de Nuit.” Though exhibit curator Sarah Kennel notes that a level of “complicity” (some of the photographs were staged) existed between Brassaï and his subjects, there’s still something fresh and different to these pictures — a sense of the unexpected or even mystical that is startlingly jarring. Brassaï, after all, wanted his images to delve into “a phantasmal and unreal Paris, plunged in darkness and fog.” Among the standouts are his photos of a pudgy streetwalker (frumpily attired in a skirt and cardigan, a cigarette sprouting carelessly from her lips), more reminiscent of a working-class housewife than a sensuous strumpet; a group of revelers at the Magic City Dance Hall decked in bonnets and glitter, who upon closer inspection emerge as transvestites; and a splendid keyhole-type view of “The Pont Royal Seen through the Pont du Carrousel,” where the glow from the riparian lights in the picture casts mesmerizing streaks across the inky water.

But it’s Dora Maar’s simple gelatin silver print from 1934 of a garish courtesan-style puppet tacked to a wooden fence and sporting heavy makeup and satin pantaloons that packs the most punch.

The scene that Maar (most famous as Pablo Picasso’s lover and “woman in tears”) highlights is far removed from the Paris of elegance and romance as peddled in guidebooks. Likely shot among the slums of the city’s dispossessed, this picture is a sad (if also surrealistic) comment on the hum-drum squalor of life’s losers — a lone garment tossed over the edge of the fence only accentuates the haphazard nihilism of the picture.

And here lies the irony of the Haussmann transformation. Though it brought new vitality, beauty and modernization to the city, it also displaced the working classes who had formerly resided in the old, cramped streets of medieval Paris, which had served as the launching pad for two uprisings in the first part of the 19th century. As Haussmann wrote, “We ripped open the belly of old Paris, the neighborhood of revolt and barricades, and cut a large opening through the almost impenetrable maze of alleys, piece by piece, and put in cross streets.” The poor were conveniently dispersed to slums on the outskirts of the city, where their ability to cause headaches for the regime was significantly weakened and where Maar’s telling photo was probably shot.

“Paris in Transition: Photographs from the National Gallery of Art” runs from Feb. 11 through May 6 in the National Gallery of Art’s West Building. For more information on exhibit-related activities, go to www.nga.gov.