Efeitos especiais desde os anos 20
When Safety Last! was made, it wasn’t feasible to insert a fake background using rear projection or a green screen, so they used a trick of perspective. The set was built at the right height for Lloyd‘s climb, but on the roof of a building across the street. As Lloyd climbed higher, the set was moved to taller buildings.
A good example of the classic movie making technique of glass matte painting. Part of the background was painted on a piece of glass, which was placed in front of the camera.