HOLLYWOOD — Desmond Ferrier can tell you from memory which of the neighborhood’s public stairways takes the best morning light, which dead-end alley reads as 1974 once you park the right cars in it, and which stucco courtyard the owner will let you shoot twice a year and not a third time. Knowing these things is his profession, and it is a strange season to be good at it.

Ferrier is a location scout, one of the people a production sends out ahead of everyone else to find the real places that will pretend to be imaginary ones. For thirty years he has driven the hills and flats with a camera on the passenger seat, building an archive that now runs to tens of thousands of photographs filed by type: bungalow courts, mid-century banks, alleys, rooftops, the flat-roofed dingbat apartments that say Los Angeles to anyone who has ever seen a movie shot here. Directors describe a mood; Ferrier answers with an address.

This year the phone rings less. The same slump emptying the soundstages has thinned the work for the people who feed them, and scouts, who freelance job to job, are among the first cut when a budget tightens. City film-permit counts are down, and a scout with no production behind him is a man with an encyclopedic knowledge of places and nobody paying to hear it. “The knowledge doesn’t expire,” Ferrier said, paging through a binder of stairway photographs in his car. “The paychecks do.”

He keeps scouting anyway, out of a habit he cannot switch off. On a recent morning he was parked below a Silver Lake staircase whose steps a neighbor had painted with rainbow stripes and two enormous red hearts — a flight of public concrete that has turned up in more commercials than most actors. “Everybody wants it, and the neighbors are past tired of it,” he said. “Half my job now is knowing which beautiful spot is already burned out from being shot too often, and steering people to the one two blocks over that isn’t.”

That kind of judgment is what worries him about the lean stretch. A location library is not a database; it is a person who remembers that a particular homeowner buried a spouse last winter and should not be cold-called for a car commercial this spring. When scouts leave the trade during a downturn, the addresses survive in a spreadsheet and the discretion walks out with them. The younger scouts who would have apprenticed on busy shows are apprenticing on nothing.

Ferrier is not leaving. He is too far in, and he still gets a private thrill when a place he flagged years ago finally lands a job and shows up on a screen wearing someone else’s story. But he watches colleagues take real-estate licenses and county gigs to ride out the quiet, and he wonders aloud who will know the hills when the work comes back. “The city sells itself as the place that can be anywhere,” he said, closing the binder. “Somebody has to actually know where anywhere is. That somebody is getting older, and there aren’t many new ones out on the road.”