Otherwise, the sky will become transparent when keying out a blue screen. As shooting outdoor usually involves blue sky, using green background to distinguish it from the sky makes sense.
Green is brighter on a digital display, thus making it easier to key out in post-production. The green screen will produce higher luminance than a blue screen under similar lighting conditions, making it cheaper for production as you don't need to purchase extra lights. You can save on lighting equipment since a green hue is easier to get lit up than the blue backdrop. Here are 5 reasons when a green screen is preferred. In practice, you probably have seen both green screen and blue screen adopted by filmmakers. In the post-editing, one will simply use the eyedropper to pick that background color and key it out. Theoretically, any solid color can be used as a background. Green Screen VS Blue Screen: Why Use Green Screen as the Background 
Plus, hold-out matte can be added to restore the image when the keying eats into the image.
Composition software usually comes with the feature to suppress the spill. Keying out the green will also remove part of the image of the subject since there is a green hue. For instance, the green screen can be reflected the sweating face of a character, especially when the light is too bright. Spill: When the color of the background is reflected on the subject, a spill occurs. Since the color needs to be uniform and distinct from the subject, green and blue screens are commonly used as they differ from human skin tone. Chroma keying is also known as color keying, or as what the broadcasting industry conventionally called, color-separation overly (mainly by BBC). Alternatively, the actors can wear green color cloth, and get removed in post-production to become invisible.
To operate the brightness level Luma keys are needed.Ĭhroma Key: It singles out a particular color from the background, making it transparent so that the subject can be composited with another background. To separate the elements by color requires Chroma keys. With this selection, one can remove it to make it transparent (green screen in VFX) or perform color grading, such as adjusting only the sky's color without affecting the environment. Keying: It is the process of isolating certain parts from the image by color or brightness. Bearing in mind these concepts, we can start to make green screen videos from scratch. The color spill is the biggest challenge during the shooting stage. What is Chroma KeyĬhroma key is one of the keying process commonly used in filmmaking, visual effects creation, broadcasting, and gaming. Things have been much easier with the chroma keying technique in post-production software, such as After Effects, Final Cut Pro, Premiere Pro, and many chroma key tools and plugins for users of all levels. French filmmaker Georges Méliès, the godfather of VFX, found the method to create matte with double exposure, American director Norman Dawn improved the matte with the glass shot, and Disney used to adopt sodium lap and prism to create a real-time matte to remove background. The idea of removing background or masking part of the scene has been existed long before the modern-day, without the help of digital video effects software. 
It ushers in a movie era with fantasy scenes that are inaccessible in real life, transports us into the deep space, and brings onto screen whatever one can dream up. Green screen is one of the most frequently adopted techniques in filmmaking.
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