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Green Screen or chroma-key technology. Goes green!

The world of cinema is composed of mystery … especially that of special effects of all kinds! Let’s look today at this famous green screen …

History:

In 1901, Georges Méliès made the film “the man with the rubber head” with a new technique: the overprint. With the help of a black background, he films several times the same scene to add elements including his own head.

Subsequently, the chroma-key technique begins to develop.
It is in 1940 that the method of the chroma key is finalized.
Indeed, in the film of “The thief of bagdad” we can see beautiful technique of chroma-key with a blue screen!

The technique is simple:

We film the set alone.
We film the character, actor.
We put filters forming negatives.
The chroma-key is made!
The technique of chroma-key remained unchanged in principle.

It is called chroma keying.

 

Green Screen:

Yes we started with a blue screen before turning to green. But why these colors?
In fact, a screen of any color would be possible. Apart from blue and green, the rest of the colors have the disadvantage of being common in shades of human skin, so that we notice the disappearance of these parts, after the chroma keying.

At present, green has become the norm: because it is the least present color in nature and on the actors, one thus limits the defects.

Nowadays, the green screen is almost systematic. Actors evolve and interact with fictional people. It has become an indispensable tool!

 

How to turn with a green screen:

  1. To know the picture of the chroma-keying with precisions (light, space …) It is the comedian who is encrusted and not the opposite. Always keep this in mind!
  2. Install the green screen.
  3. If we make plans in motion: we need to know tracking + 3D effect …
  4. For still shots (easier to do): do not hesitate to add objects in your stage but do not put any green!
  5. Position your lights! It is essential to have a PERFECT green screen (without crease or shadow) otherwise we have artifacts. These artifacts occur especially when the green background is not lit homogeneously; or for example, in the hair because of the halos that the intense green of the screen sometimes creates there.
    To avoid this, place your actor a good distance from the green screen, over-illuminate your green screen and place a light behind your actor to mark the contrast between the character and the key.
  6. It only remains to turn: ACTION
sources:
https://www.lemonde.fr/culture/video/2013/03/07/le-fond-vert-grand-pere-des-effets-speciaux-ne-en-1940_1843938_3246.htmlhttps://jcinema.wordpress.com/technique-cinema/incrustation/