Lucas convinced Coppola to let him shoot a cinema verité documentary on-the-road with Francis Ford Coppola's The Rain People (1969).
The $12,000 budget for the short came out of the still photography budget of The Rain People itself, and Lucas scrapped his way to the 16mm camera and did all of the film and sound work on his own, while writing the screenplay for THX 1138 at night.
As a look into the early days of New Hollywood, and in particular the flamboyant character of young Francis Ford Coppola, this documentary is nothing short of amazing, showing him at his very best, wheeling and dealing with the studios over the phone, hamming up the drama and bending over backwards to get his will. It's also interesting simply because it shows more of Lucas's signature style, with several long lens shots akin to those from his student films and his later full feature films. Also on display is his propensity for placing text in the lower part of the frame, and to the right, often in lowercase and (from what I can tell) set in the same sans-serif typeface.
As near as I can tell, it wasn't released until late 1977, even though The Rain People was released in 1969, although I don't know what would have kept it in the vault for that long, or why it would end up being released in 1977 when Lucas had other things on his mind.