Disney Studios also created what became known as the Leica reel by filming storyboards and editing them to a soundtrack of the completed film. This technique was essentially the predecessor of modern computer previsualization. Other prototyping techniques used in the 1930s were miniature sets often viewed with a “periscope”, a small optical device with deep depth of field that a director could insert into a miniature set to explore camera angles. Set designers were also using a scenic technique called camera angle projection to create perspective drawings from a plan and elevation blueprint. This allowed them to accurately depict the set as seen by a lens of a specific focal length and film format.