Green Screen is a Nuke workflow tool that creates a virtual background that can be used in any field of production. IT is great for photo-realistic visuals or as a simpler alternative to painting effects and other techniques. It is a powerful Nuke template used in computer graphics fields, such as film and TV. Green Screen is a popular choice for you to create stunning background scenes quickly and easily
Changing or extracting the green screen can be done in various ways. The technique differs according to the plate or the result that is needed. Sometimes, instead of extracting the color, what an artist needs to do is suppress or de-saturate a specific color according to the reference.
Suppressing a color refers to reducing the amount of green that is used in a specific plate. It increases the range of areas that are color suppressed. If the color you want to suppress is still evident, increase this value. Along with this, we also have to de-saturate the color, where we completely remove the color or. For example, we completely remove the respective color value. For example:-
Here we can see, different techniques gives us various output. when we suppress the green value, we just remove the value of green but the value of other colors stay intact. Where as if we de-saturate the color, we totally remove the value of the colors, making it ‘De-colored’.
here we can see another reference for the color suppression and color de-saturating. For 1st instance we just play with the value of the color green, where the other color values are untouched, where as for de-saturating, we completely de-color which gives results into a gray scale.
The other technique for extracting a specific color, is by using the “keyer” node. With the help of this node we can extract the primary colors, i.e. green, blue and red. But this node is not only restricted to the colors, we can also play with the luminance and the saturation of the plate.
In the below example, we can see how i have extracted the white (luminance), as i wanted to see how the node works. I extracted the sky, eve though its not perfect, we can clearly see how powerful this node is, in which we can play even with the slightest part or color as per needed. In here we have to select the keyer that we have to do the changes. After this we have to manipulate the bars or handles where we can get the result that we need, i.e. extracting the color.
Here is an another technique, where we can get an alpha from the color which we need. For example, over here I extracted the color red, and subtracted it with the rest of the plate, which resulted into giving me the blacks and whites of the plate. These blacks and white represented the alpha, white being 1 and black being 0. And with the help of the we get our alpha on which we can color grade the plate as per the alpha.
So we’ll do a shift command or control sample of a large area of the green screen in order to identify the hue of green we want to spill suppress. And I’m going to use a combination of Saturation and Green Suppression Curves with the help of the Keylight node. So I pick the color, so I can move their control points to be right centered on my target color. Because as I make adjustments it’s going to move the darkened thing off the spot. So, we’ll start by taking the Saturation down. That gets rid of some of my green spill. Then we’ll merge the difference and color correct the plate. And through this step we can color correct the plate and reduce a bit of spill.