The Screen Magic

Did you know all those dangerous stunts performed in movies like Star wars, Spiderman and more were not real but scenes shot on two different backgrounds? Even wondered how those not-existing-on earth backgrounds enhance a movie? Thought about composite photographs - exposing the layers to blend in the elements? Or ever wondered things like these were possible??

Chroma key compositing is a special effects post production technique. The technology is the basis of effects seen in everything from Hollywood movies to weather forecasts to video games. The concept is simple and extremely useful. 

The images or videos are composed and layered together on the basis of a chroma range (green or blue is often used). Using softwares like Adobe After Effects, the top layer is made to disappear revealing the background behind.

-.- Superman -.-

-.- Avengers -.-

-.- Narnia -.-

The biggest challenge when setting up a bluescreen or greenscreen is even lighting and the avoidance of shadow, because it is best to have as narrow a color range as possible being replaced. A shiny surface will have areas that reflect the lights making them appear pale, while other areas may be darkened. A matte surface will diffuse the reflected light and have a more even color range.

(Source: http://thechive.com/2013/01/28/a-staple-post-production-visual-film-effect-14-photos/)

The video below takes you through the history of movie making using green and blue screens.