how rotoscoping works - old school projector

The old school character positioning with special effects is not just about making animated films.
It was used to add special effects to the 1963 film Bird by Alfred Hitchcock, putting all glowing lightsaber blades into the original Star Wars trilogy, and add effects to many other movies.
In the days of shooting and editing movies with actual film, rotoscoping is sometimes used to draw special effects on animation cells
Action lens, but it is also used to create mattes (or masks)
Allows filmmakers to combine elements of one shooting scene with elements of another completely different shooting scene.
Filmmakers may want to superimpose a person's lens on a lens in the background of a certain position, such as the ocean or outer space, or before the explosion.
This combination of images or effects originally not taken together in a movie frame is called synthesis.
This kind of rotoscoping is a very time-consuming task, like its animation, which involves projecting each frame of film onto a glass plate and manually tracking an item at a time.
Animators or special effects artists will track any elements that need to be isolated to transparent cells.
The elements tracked will be filled with paint to create mattes that can be placed at the top of another frame (
Such as the required background material)
In order to effectively block the area on the frame and leave a position for the foreground effect.
This process usually requires the creation of multiple film reels, such as original foreground and background image footage, black pantomime with black background and movie with negative version of pantomime.
To combine all the elements together, a new film will be exposed multiple times.
The background image will be exposed to the film with a black matte in front and the foreground element will be exposed to the same frame film with a negative version of matte on the front, to expose the foreground element to the first exposure on the film left to it
In this way, rotoscoped mattes are used to combine the foreground elements and background to each frame of the movie.
A lot of work is needed to do it well.
The typical 35mm film is projected at a speed of 24 frames per second, which means 1,440 frames per minute, so mattes need to be drawn for dozens, hundreds or even thousands of frames.
In a single action shot, the moving item changes the position slightly in each subsequent frame (
A matte that changes position and shape from frame to frame is called a moving matte).
When multiple things turn in and overlap on the screen, it becomes more complex and requires multiple mattes per frame.
Not only does it involve a large number of frames, but the outline and drawing details of each frame need to be detailed and the lighting must match (
Or match later by color correction)
And all the physical elements (
(Film and equipment)
Must be fully queued, otherwise the result will move strangely or it will not look appropriate.
But, if done well, rotoscoping can be used to show things in movies that are hard or impossible to shoot in real life.
This is also for more common but necessary purposes, such as intentionally or inadvertently removing cables, microphones, stage marks, or other items left in the lens, this may cause the audience to lose interest while watching the film.
This technology has been used to some extent so far, but thankfully, there is a more modern way of rotoscoping, creating mattes, and synthesizing elements in the computer age.