It was such a huge error, Martin Scorcese had to go back and correct it frame by frame.
On Thanksgiving Day of 1976, The Band played its last concert ever, at the Winterland Ballroom in San Francisco. They invited some of their friends, who happened to be some of the biggest names in music at the time–Bob Dylan, Eric Clapton, Joni Mitchell, Neil Diamond, and many others, including Neil Young. The whole thing was filmed by Martin Scorsese and became the basis for his 1978 movie, The Last Waltz.
Backstage was a huge party, where the world’s biggest musicians would have to stop doing drugs long enough to go out and play some music, as told in the vivid account of this incident on the site Death and Taxes.
When Neil Young came out to perform, he had what The Band drummer Levon Helm called a huge cocaine booger stuck to his nostril.
The legend goes that when Neil’s management saw the footage, they wouldn’t let it be used. So Scorsese had the cocaine removed frame by frame using a process called rotoscoping.
It was such a time-consuming and costly process, that footage of Neil Young performing one song was the most expensive shot of Scorsese’s career up to that point.