Last fall, Annie Leibovitz, the photographer, borrowed $5 million from a company called Art Capital Group. In December, she borrowed $10.5 million more from the same firm. As collateral, among other items, she used town houses she owns in Greenwich Village, a country house, and something else: the rights to all of her photographs.

In other words, according to loan documents filed with the city, one of the world’s most successful photographers essentially pawned every snap of the shutter she had made or will make until the loans are paid off.

Those who know Ms. Leibovitz said she used the money to pay off mortgages and deal with other financial stresses. But whatever her reasons, she is not alone in doing business with Art Capital and similar lenders. At a time when stock portfolios are plunging and many homes, even grand ones, have no equity left to borrow against, an increasing number of art owners are realizing that an Old Master or a prime photograph, when used as collateral, can bring in much-needed cash.

“It’s very discreet,” said Ian Peck, a co-owner of Art Capital.

This little-known corner of the art business is lightly regulated and highly litigious. But this has not dissuaded clients who have included rich collectors like Veronica Hearst, art galleries and prominent artists themselves, including Ms. Leibovitz and Julian Schnabel.