LOS ANGELES (Reuters) - A new wave of investors is scooping up stakes in films from private equity and hedge funds that have poured $10 billion into Hollywood but are losing patience with long wait for profits, industry watchers say.

Hedge funds and private equity firms bought up pieces of many Hollywood films, both big budget and art house-sized, in recent years, and money keeps pouring in from all over the world fattening film budgets and adding more titles to theater marquees.

Byzantine movie accounting rules provide that lenders, distributors, theaters and profit participants such as actors and directors, take the first cut of profits, so that a film that clears $100 million at the box office may not immediately return money to its private equity and hedge fund backers.

Movie profits trickle in over nearly a decade of releases to theaters, DVD, television and cable TV. That time frame may not suit investors typically used to five-year returns, said Tom Adams, who heads Adams Media Research.

"(Movies) take two to three years to make and then they're in the red for substantial amounts of time," Adams said. Hedge funds, which buy and sell securities rapidly, have even shorter time horizons for expected returns a factor that may make them uneasy partners with Hollywood. Attorney Alan Schwartz of Greenberg Traurig in Los Angeles, who has represented both sides producers and financiers said that the movie industry's long cycle also makes it hard to tell if film slates are profitable.

"(Investors) are beginning to shows signs, in some cases, of irritation and concerns: 'The pictures all did terribly what the hell is going on here'?" Schwartz said.

Movies financed with private equity and hedge fund dollars include huge moneymakers like Warner Bros.' "300," which grossed $456 million at global box offices, and the studio's "Blood Diamond" and "Poseidon" titles, considered flops that grossed $171 million and $181 million, respectively.

Each of the six major Hollywood studios has made at least one deal to share film production costs with private equity investors who have purchased shares of a film fund.

The fund typically invests in a slate of 12 to 20-plus movies to be produced and released over several years and reaps a share of profits after expenses are paid.

Echoing other studio chiefs, Lion's Gate Entertainment Group chief executive Jon Feltheimer in May touted slate financing as a way "to maintain our conservative risk profile" while growing the company's film business.

In a report set for release in August, Adams Media Research concludes that while the studios' film costs are flat, private equity is picking up the tab for bigger-budget productions that are taking longer to pay back investors.