When the street photographer James Prochnik started taking pictures in Chinatown, he found echoes of the movie in the ubiquitous red shopping bags that filled the neighborhood. At the right hour, when the sun was low in the sky, the bags appeared lit from within, an array of Chinese lanterns glowing benevolently in the crowded streets.

In other neighborhoods, including Bay Ridge, Brooklyn, where Mr. Prochnik lives, shopping bags come in all colors — nothing to shoot there. But in Chinatown, where the red symbolizes good luck, red trumps all other shades. Some bags carried produce from street markets; some carried nothing but air, buoyed aloft on steamy updrafts.

Mr. Prochnik, 52, saw the bags as symbols of continuity and identity in a city where ethnic enclaves are everywhere threatened by gentrification. And the bags themselves are threatened by proposed legislation to ban them or impose surchargeson each bag.

“They’re a symbol of the resourcefulness and hardworking nature of the Chinese community in New York,” he said.

“I support the environmental concerns for banishing them, but it’ll be a loss.”

In the more recent movie “American Beauty,” a character videotapes a white plastic bag swirling in a winter breeze, and says, “This incredibly benevolent force wanted me to know that there was no reason to be afraid, ever.”

Mr. Prochnik found a similar message in the bags of Chinatown: that good luck can be summoned; that gentrification can be suspended; that Chinatown can remain Chinatown, even as the rest of the city transforms around it.

“The color almost manifests that belief in good luck, happiness and wealth,” he said. “They take on a magical quality.”

And after they have served their function of ferrying Chinese broccoli or cheap mangoes, Mr. Prochnik sometimes uses them to filter the light of his camera flash. Because good luck is something we should never squander or discard.