Developing Technologies TG : Bedknobs and Broomsticks 1971

http://www.traileraddict.com/poster/bedknobs-and-broomsticks/3

Bedknobs and Broomsticks is a beloved film that is full of special effects. However back in the 1970s the special effects were done a lot different from today. But they are still the same basic effects. The techniques used back then created the effects that are used now.

The Effect.

They used an effect called Sodium Screen Vapor Process. This was created by Disney and is used in many of there films during the 60s and 70s like Mary Poppins and Petes Dragon. They would film the bed and the characters against a screen that was all yellow. The camera they used to create this is a three strip technicolor camera, this camera had two film movement built into it and then a prism that only gets rid of the sodium color lights. this technique means they have two different films, 1 would have the color image which is the bed with no background and the other would just have the background with the shape of the bed and characters silhouetted. This effect was used through tout the film, it was the only effect they used.
Back then there was a machine called an optical printer that re photographed all the differant pieces and layers of film to make one.

http://www.technifex.com/portfolio/walt-disney-family-museum-2

This effect is the same as green screen. All the techniques that are used today where used back them however unlike the 70s we use computers.