But what were 486 frames of 8-millimeter film actually worth? Although I agreed to help, I hadn't the vaguest notion of how one went about appraising a motion picture, let alone one that documented such a pivotal moment.

I enlisted the help of C. Cameron Macauley, a former colleague at UC Berkeley, whose knowledge of photographic history had led to a second career as an appraiser of still photos for museums and private collectors.

Abraham Zapruder sold his film to Time-Life Inc. the day after the assassination for $150,000 (equal to just over

$1 million in today's money), and Life magazine's editors, in their wisdom, decided that the public should never see it as a moving picture, but only as still pictures taken from its frames. Even Walter Cronkite couldn't get his hands on it, much to his fury. ("We believe that the Zapruder film is an invaluable asset, not of Time, Inc., but of the people of the United States," he intoned to the camera.)

For complicated reasons, Time-Life eventually sold the film back to the Zapruder family in 1975 for $1, and later that year, courtesy of Geraldo Rivera, the public saw a pirated copy, in its entirety, for the first time.

Three years later, attorney Henry Zapruder asked the National Archives to store the film "for safekeeping," believing he could get it back any time. But in 1992, Congress passed the JFK Assassination Records Collection Act, mandating that everything related to the killing be held by the government, which, the archives stated, prevented it from returning the film to the family. Henry Zapruder argued that this constituted a "taking" of private property and that the government owed him a breathtaking $30 million.

Macauley and I went to see it for ourselves.

The dustproof room where we examined it resembled a scientific lab, and we had to wear white cotton gloves before handling it. The film at an earlier time had been stored in a cardboard box for an extended period and was thus exposed to varying heat and humidity conditions. It had shrunk in length, making it dangerous for additional copies to be made from it without risking severe damage to the original film.

Dust specks and dirt had been ground into the film's surface during rewinding, and we found many scratches, as well as two splices where it had accidentally been torn by a Life technician. In spite of these flaws, the Kodak film stock still retained its original brilliant color with no signs of deterioration over the 35 years since the film was exposed.

Professional appraisers begin by asking three questions of an item: (1) How much would it cost to replace it? (2) How much income is it capable of producing? and (3) What is its value on the open market?

In this case, the Zapruder film was irreplaceable. As for how much income it could produce, in the decades since the assassination, the Zapruders had realized about half a million dollars from the film — including $50,000 from Oliver Stone for its inclusion in his film "JFK."

Even when we adjusted the original $150,000 sale to Life magazine up to $784,065, to account for inflation, the total realized by the Zapruder family was still a far cry from $30 million. And the Zapruders retained the copyright, so they were free to continue their earnings by leasing copies of the film.

To support his interpretation of the film's value on the open market, Zapruder's lawyer William Bennett pointed to auction records that showed that collectors snapped up Kennedy-related items at outlandish prices (e.g., tens of thousands of dollars for Jackie's cheap costume jewelry, $40,000 for a cigar box used by JFK, and a set of his golf clubs sold for 800 times their original cost). Since still photos are sometimes compared with the movies they appear in, Zapruder's advisers cited the case of Alfred Stieglitz's famous 1907 picture, "The Steerage," which had sold at Sotheby's for $17,250 in 1955.

Since there were 486 individual pictures that made up the original footage of his father's assassination film, Zapruder claimed that, using Stieglitz math, the assassination film's value was worth at least, $8,383,500.

But a better comparison, he argued was with the famous Leonardo da Vinci Leicester Codex. Bill Gates had recently laid out $30.8 million to acquire it — at that time the most ever paid for an object at auction — and Henry Zapruder claimed that his strip of film was at least as valuable. Furthermore, Zapruder said he'd been offered $1.5 million for just 10 frames. But then it transpired that he had various business connections to the man making the offer, which raised the suspicion that the offer was naught but theater.

And so it went, back and forth, month after month, as the parties tried to convince one another of the validity of their positions. On Oct. 20, 1997 the Zapruders made an $18.5 million settlement offer. Based on the work done by Macauley and me, the government made a counter-offer of one-sixth as much.

After years of discussions across the conference table, the parties agreed to arbitration in Washington by a panel of three retired federal judges who listened to all the arguments for three days and then split the difference, awarding the Zapruders $15 million plus $1 million in accrued interest.

The Zapruder film has been much on my mind lately, and not just because this year marks the 50th anniversary of the assassination. Today we are learning — through the actions of Bradley Manning, Edward Snowden and Julian Assange — a lot about our shared experience that our government doesn't want us to know.

Fifty years ago, it was corporate America, in the body of Time-Life, that was keeping the secrets, while Congress saw its role as safeguarding the evidence about the Kennedy assassination, precisely to make it public. History might have been rather different had there been no attempt in 1963 to limit what the public knew about the killing of a president.

Many of the conspiracy theories might never have gotten off the ground.

The Zapruder film story also provides insight into what defines value in our culture. The Zapruders were compensated for the "taking," but what benefit did taxpayers receive? Must an object's value be judged only by how much it can bring in the world of commerce, or is there also another kind of worth defined by its role in history as part of our public trust?

After a half-century, the Zapruder film story may have come to an end, but some of the questions it raises still linger on.

Ernest D. Rose, a former UC Berkeley professor and documentary filmmaker, is a resident of Oakmont in Santa Rosa.