Research and Understanding Green Screen

Green Screen:
Green Screening can be referred to as key compositing or chroma keying, it is a special effects post production technique for compositing two images or video streams together based on colour hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video - particular news casting, motion picture and video game industries.
The main key points of green screening and why it is used so frequently nowadays is to create a background that is realistic and is easy to get rather than travel to find that place such as a New York city, companies use green screening because for example: in 'Black Betty' during a scene where Betty is in the city and runs into a bus stop, this is all green screened for if they did it in actual New York city, not only would they need to worry about the other members of the public, either getting in the way or stopping and staring during the scene, but they would have to worry about the background sound, for there would be a lot of noise outside which could stop Betty being as well heard during her dialogue.
It is also a lot cheaper using green screen rather than travelling form country to country. To do green screening you cover a green blanket over a straight wall, or board so that there are no creases and then act around the green screening, then when the film is put onto the computer you add the background Image to the film - wherever the green screen is.
Green Screening was used in 'Ugly Betty', It was used in 'Black Betty' because most of the scenes during this film is based in New York city, and if they filmed in this location it would take a lot longer to catch, for they would need to think about traffic, and other members of the public, also if they were to film in this location they could have members of the public walking through their footage or stopping and staring, they could also end up having a lot of interruptions with sound for the traffic sound could interrupt and public noise could stop Betty's dialogue being heard.
  
The video above is of different movies that make it look as if the actors look as if they are in a location, although in reality when filming they are actually just walking about through a load of boards covered with green screen. This also shows the filming of 'Ugly Betty' that I was previously talking about when running into the bus stop, and the people in the background that look like they are walking around the city but actually just walking about on a green screen covering the floor, then replaced with an Image in a program on a computer such as: Photoshop, After Effects, Premiere Pro etc.