Warner Bros. has benefited more than most from a half-century of media mergers. In 1956, the WB library was sold to PRM Inc., which became Associated Artists Productions, which, in 1958, sold the assets to United Artists. MGM bought United Artists (and hence the Warner library) in 1981. Turner Broadcasting bought the rights to MGM films made up until 1986. Finally, in the late '90s, Time-Warner bought Turner, which brought the Warner library home—and the classic MGMs, too. When UA held the rights, it donated pre-1949 Warner Bros. nitrates to the Library of Congress and post-1951 negatives to UCLA's film library. RKO is a more complicated story. When that studio was sold in 1957, its holdings were scattered. To make DVDs of such RKO classics as Citizen Kane (a superb transfer, even though the original negative was burned in a warehouse fire), Bringing Up Baby (coming out next month), and a series of Fred Astaire-Ginger Rogers films (five later this year, five next year), Warner executives have hunted down elements from as many as seven archives, in the United States and Europe, piecing together the best-preserved pieces from each to form the best-looking master.

I should note that other DVD companies—most notably the Criterion Collection but also Columbia, MGM, Paramount, Universal, and several more—also spend huge sums to track down elements for many DVD projects.