HOLLYWOOD — Sal Prima painted the sky for a living, and in fifty years on the job it never once rained on his watch.

Salvatore Prima, a studio scenic painter whose backdrops stood behind Westerns, war pictures, musicals and the occasional shipwreck across the second half of the twentieth century, died July 4 at his home in the Franklin Hills. He was 94. His daughter said the cause was heart failure.

Mr. Prima belonged to a trade that the camera was designed to hide. When a film needed a horizon — a desert running to purple mountains, a Kansas sky the size of a barn door, the false depth of a city street that ended forty feet from the actors — it fell to painters like him to build that world flat, on canvas and plaster, at a scale that made no sense up close and perfect sense through a lens. He could stand six feet from a wall he was painting and see only abstract smears of color; the illusion assembled itself for the camera and for no one else.

“Sal’s clouds looked more like clouds than clouds do,” said Devora Nash, a retired art director who worked with him across three decades. “A real sky is boring. Sal knew a real sky wouldn’t read on film, so he painted the sky you remember instead of the one that’s actually up there. That’s the whole job, and almost nobody could do it.”

He was born in 1932 in Boyle Heights, the son of a sign painter, and learned the trade the way most scenic artists of his generation did — as an apprentice, mixing colors and cleaning brushes for men who did not explain themselves and expected you to watch. He joined a studio paint department in the early 1950s and stayed in the work, through the collapse of the studio system and the rise of everything that was supposed to replace him, until he set down his brushes in the early 2000s, by then one of the last men in the city who could size a backdrop by eye.

The arrival of digital backgrounds did not embitter him, colleagues said, though it ended his trade. He allowed that the computer could paint a sky faster and cheaper. He maintained, to the end, that it could not paint a sky you’d miss.

Mr. Prima is survived by his daughter, Renata Prima of Glendale; a son, Anthony Prima of Portland, Oregon; four grandchildren; and two great-grandchildren. His wife of fifty-one years, Iolanda, died in 2019. A memorial is planned for later this summer.

One of his last backdrops still hangs, rolled and stored, in a studio scene dock across town — a summer sky, cloud-piled and impossibly deep, painted for a picture that never got made. Every so often, his daughter said, a crew unrolls it for something else and pauses, not knowing whose it is, to look up at a good day that never happened and never ends.