Optical printer

Okay, so imagine you have a toy printer that can print pictures. But instead of printing with ink, it uses light to make the picture.

First, you take a piece of film that has a picture on it. This film is like a negative – it has the opposite colors of what the final picture should look like. For example, a black area in the film means there should be white in the final picture, and a white area in the film means there should be black in the final picture.

Next, you put the film into the printer and turn on the light. The light shines through the film and onto a new piece of film that doesn't have anything on it yet. This new piece of film will become the final picture.

As the light shines through the film, it makes the opposite colors appear on the new piece of film. So if there was a black area in the film, it would make a white area on the new piece of film. And if there was a white area in the film, it would make a black area on the new piece of film.

You can do this with different colors of light and different pieces of film to create a really cool final picture that has all sorts of colors and shapes. Optical printers are used in movies and TV to add special effects or combine different pieces of film together.