
Strictly speaking, an independent film is one which is made away from the control of a large corporation, and by control we mean funding or creative input. So no film could really be called an independent film unless it is totally funded produced and distributed privately. It is therefore unlikely that any film can truly and totally be called an independent film.
It has been said that if 50% of the budget is raised away from a major studio it would be an independent film but this is debatable since a studio with a 50% investment would certainly not leave the production alone but would exert plenty of influence. Also, this begs the question of what is a ‘major’ studio as often smaller studios can morph into bigger players (see below). Certainly, if any money comes from a major, it would be a small part of the budget.
Independent cinema is therefore more of a relative term and it has come to mean that there is less input or interference from the large film companies (i.e. the Hollywood companies, Warner Bros, Disney, 20th Century Fox and Paramount, etc.) than in a mainstream film.

Ironically, as producers seek to assert their independence from the big companies, often by starting their own smaller companies, they can become what they seek to distance themselves from as George Lucas admits.
He established Lucasfilm so he could be...

