Light leaks are the incredible effect you get when the back of a film based camera is opened. Usually you do this mid-roll, meaning you get a bit of the film pulled out of the canister before you open the camera back.
Here is a great article with much more info at thedphoto.com.
One of the great masters of this style commercially is Mark Borthwick.(click to google his pics)
He has an excellent book
that you can buy, it includes many of of his better photos, and is curated by Beautiful Losers founder Aaron Rose.Here are some of my favorites of his...
