Willis H. O'brien and Stop Motion in early Film
It wasn't until the 1930's that Stop Motion began appearing in feature films most notably in Merian C. Cooper and Ernest B. Schoedsacks King Kong. Willis H. O'brien was the visionary behind the stop motion effects in this film which was groundbreaking at the time. O'brien got involved with this project ironically due to his work on various other projects that were unsuccessful. these production were costing to much money and yielding little footage for the time and effort. Merian C. Cooper was the one to actually pulled the plug on these projects. Realising O'brien skill however he put him to work on a new project which would later develop into King Kong.
He would later go on to heading the special effects team on the movie Mighty Joe Young, for which he won an academy award. Ray Harryhausen was hired as O'briens assistant which was his first job on a film, Harryhausen actually ended up creating most of the animation on the film, which helped boost his own career.
The Link below shows a variety of interviews about the stop motion process and specifically to Willis O'briens work on King Kong. It gives some real insight into the pain staking effort it takes to create a functioning piece of stop motion footage. For example when shooting a sequence the team would have to finish the entire thing within the course of a work day, even turning the lights off and on between days would result in different light intensity therefore coursing shadows on the set to be different from frame to frame. I found it very useful in researching this topic.