A new kind of movie mania is on the loose, and it has thousands of Americans reaching for checkbooks instead of popcorn.

In the first six months of this year, investors have put up more than $200 million to help finance movie productions through the sale of limited partnerships to the public. That compares with just $60 million for all of 1984, according to Robert Stanger & Co., which tracks limited partnerships.

More than half a dozen companies are selling stardust dreams through major brokerages for $5,000 or less a pop. This year, public partnerships surpassed private shelters, the traditional vehicle for movie investors, as a source of movie funding. Stanger reports that private partnerships have raised only $48.9 million this year.

Movie partnerships make up less than 1 percent of all limited partnerships, but the number is growing. Silver Screen Partners, sold by E. F. Hutton & Co. Inc., has raised $148 million thus far in 1985 for Walt Disney Productions and expects to reach $200 million by year-end. Delphi Partners, sold by Merrill Lynch, already has raised $40 million this year and plans to seek a similar amount in an upcoming issue to finance productions by Columbia Pictures Industries Inc.

Silver Screen and Delphi have been organizing partnerships for several years, but newer and smaller companies also are springing up. For example, Balcor has raised $15.5 million for New World Pictures. Minimum participation is $3,000. Others that have raised little or nothing yet include Black Widow Productions, Cinamerica Film Bank and Pennington Productions, according to Stanger's analysis of registration statements.

Movie moguls once relied on private investors. But a change in the 1976 tax laws abolished the ability to write off 100 percent or more of an investment. As interest rates soared in the early part of the decade, bank credit dried up. A cheaper source of funds was needed.

Given Middle America's fascination with Tinseltown, what could be more natural than to tempt starry-eyed investors with the prospect of having a stake in multimillion-dollar blockbusters, attending a premiere or mingling with actors and directors on the set of "their" productions? Investing in the cinema, after all, is a lot sexier than municipal bonds or cattle-feeding shelters.

Today's film partnerships are structured in several different ways, some riskier than others. Each partnership's portfolio is composed of a number of movies from which the investor reaps the rewards -- either singly or collectively -- as the films are made and released. One-third of the films in a typical portfolio are winners, explained Jeff Radow, vice president of Delphi Financial Services Corp. in New York; another third lose money, and the rest break even.

A film's box office gross represents only part of the pot; the rest comes from cassette and album sales, network and cable television rights and foreign syndication. All the expenses of promotion and advertising, plus the distributor's hefty share, are subtracted from the gross. Limited partners then share the net proceeds with the general partner on a pro-rata basis.

Historically, the movie business has been considered very risky. Traditional film partnerships feature a tax write-off as a reward for risk-taking, but some newer ones offer no shelter because they promise to return the entire initial investment over time regardless of how well the pictures do. A money-back guarantee plus all the glamour would appear to be ideal for the romantic investor, but how realistic is it, financially speaking?

The Washington Post asked a financial planner to analyze the returns on two seasoned partnerships and compare them with Treasury securities as well as with the common stock of the companies producing the films. Mary Malgoire, a certified financial planner and a principal in Malgoire Drucker Inc. of the District, found that, in one case, the common stock proved a better investment than the partnership, and, in the other, Treasury securities yielded more.

Delphi I, issued in July 1982, raised $50 million from investors for Columbia Pictures. The studio, which was taken over a month earlier by Coca-Cola Co., contributed an additional $10 million. The partnership has an interest in 19 films released to date, including such blockbusters as "Tootsie," which grossed $171 million at U.S. box offices; "The Big Chill," which grossed $54 million; "Ghostbusters," with $221 million; and "Blue Thunder," with $42 million. Profits from the winners helped offset losses from such unmemorable flops as "Sheena, Queen of the Jungle."

Delphi executives estimate that the 5,900 limited partners will earn between 120 and 150 percent of their original investment over the 10-year life of the shelter. This assumption includes proceeds from a planned sequel to "Ghostbusters" and the sale of a film library.

The contract calls for limited partners to get 80 percent of net proceeds after their original investment is paid back; the general partner gets the other 20 percent. Because there is no guaranteed return of principal, Delphi I offered investors a 71 percent write-off in the first year plus $350 of investment tax credits over three years.

Using a taxpayer in the 50 percent bracket as an example, Malgoire calculated that the investor putting up $5,000 saved $1,775 in taxes the first year. With the tax credit and cash distributions of $2,375, the investor has gotten $4,500 back so far. If the shelter returns 120 percent over 10 years, the after-tax annual yield to the investor will be 9.3 percent. If the return is 150 percent, the investor's 10-year yield will be 12 percent.

By way of comparison, if the investor had put $5,000 three years ago into Coca-Cola common stock, which was selling at 37 1/2, and sold it this week at 71 1/8, the after-tax annual return on capital gains and dividends would be 22 percent. Of course, the future course of Coke stock cannot be anticipated, but even if the price stayed the same for the next seven years, the 10-year return would be 7.7 percent, according to Malgoire.

Ten-year Treasury securities bore a 13.93-percent interest rate in July 1982. Today, a $5,000 investment would be worth $5,648, a 10.8 percent after-tax return. In 1992, the after-tax return would sink to 6.9 percent.

Silver Screen I, issued in September 1983, raised $83 million for Home Box Office, a subsidiary of Time Inc. Its 13,000 limited partners have an interest in eight movies, of which three have been released. "Flash Point" took in a disappointing $4 million at the box office; "Heaven Help Us" grossed $6.5 million; and the recently released "Volunteers" grossed $12 million.

The first two have not yet made enough to cover their costs, but Roland Betts of HBO said cable and other contracts would bring the return on "Flash Point" to 128 percent of cost and on "Heaven Help Us" to 125 percent. In her calculations, Malgoire assumed a 150 percent return on the more promising "Volunteers."

Silver Screen guarantees a total return of principal, so there is no write-off. A 20 percent cash distribution already has been made. After investors get their initial investment back, they will receive 85 percent of net proceeds.

A 120-percent payout over the eight-year life of the partnership would return 2.2 percent annually after taxes, Malgoire calculated; a 150-percent payout, 4.9 percent.

Time Inc. common stock fell from 67 1/4 to 57 1/2 in the same period. A similar investment in this stock two years ago, including dividends and earnings from a unit that was spun off, would yield 2.3 percent annually after taxes if sold this week. The same amount put into a 10-year Treasury security paying 11.69 percent would be worth $5,312 today, an after-tax return of 8.8 percent, declining to 5.9 percent over eight years.

So the movie partnership placed second of three investments in one example and last in the other. One partnership showed a healthy return; the other, far less than one could get at a bank. Malgoire, a fee-only planner, said the exercise confirmed her reluctance to go into movie partnerships.

David S. Dondero, an Arlington planner specializing in tax shelters, was more emphatic. "Anyone going into a movie deal is shooting craps," he said.