“Let’s just film in front of green! That way, we save ourselves the effort of constantly building new locations!” Or: “We need to have another go at a scene. Perhaps we’ll do that in front of the green screen, then we can just implement it into the other scenes.” These are all examples of customer statements – mostly expressed with great enthusiasm… However, we have to destroy this illusion of the ‘green solution’ pretty quickly, as filming in front of green is unfortunately not always the solution for everything.
Let me explain: A green screen is a green wall (fabric, wall paint, etc.) in a deep glowing green. Often, you also hear the term ‘blue screen’, which works along the same principle – only difference: it is blue. But why green or blue? Because these are the colors that are least common in our skin pigments. This makes it easy in the postproduction to separate foreground (the person) and background (the green / blue screen) with the software programs . The process of replacing the green with another background during the post-production process is called ‘chroma keying’.
When does filming in front of the green screen make sense?
A. From an artistic point of view: If you want to show your protagonists in places that cannot be shown in reality or only under very difficult circumstances. For example, the scenes of the collapsing high-rise buildings in “Inception”, the flight scenes from “Harry Potter” films or the below scenes here from “Avengers”.
B. From an organizational point of view: If you want to film several people in the same location to save time, but the scenes should not look the same or only slightly similar. For example, if you want to interview several customers who are attending one of your events.
So, if you don’t want the audience to see Harry Potter hovering on his broom inside a green room, the postproduction of such a movie gets very busy: A dozen employees do nothing else for months but work on the individual images (so – called frames) of each scene so that the transitions between foreground and background are smooth and the perspective is correct. A frame is 1/24 of a second in the movie. Yes, you read correctly: 24 individual images for only one second of film! Now it might become clearer why so many people have to work for such a long time.
To be continued: Part 2 of this article will be released on January 9th 2017.