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.

Creating the mood and coherent sensibility by using the color palette is known as color grading. Colour grading is adjusting the image in specific ways to create a stylistic effect. For example ‘crushing’ the blacks of an image to make it feel contemporary, or taking the matched shots from a camera and tracking and lightening main characters face so that they stand out.

Grading of the plate is a process where the film scans are color graded to the look
wanted by the movie directors for their projects. Usually, these color grades are finished
by using a LUT which is used in order to enhance the mood of the videos. For example,
for getting a look of danger or horror a Dark LUT is used, where as that used for a happy
occasion is usually brighter. After the process of color grading the output is used for
plate preparation i.e., main look of the shot which is going to be carried forward in
Compositing.

The Main task of this was to color grade the dragon in such a way that it will match the background and merge it together. ‘As if it was one’ was the motive for this project. In this area, usually the best technique that we can use is, gaining the information of the color (blacks and the whites). Through analyzing this, we can match the color the object by grading it according to the background.

In the grade node we have to match the blacks and white. For doing this we have to do the following:

1. Pick the darkest color of the Dragon so that we can change it accordingly.
2. After picking the dark point, we have to lift it up according to that of the back ground. For doing this we have to pick the dark color of the background. (It has to be done the the lift setting)
3. Similarly, we have to pick color for white point and gain, but over here we have to get the brightest part of both. As this is going too set the overall mood/theme of the Dragon.

(Please refer to the node below)

I have done similar technique for other project (Refer to the images below). This techniques work the best for getting faster result and correcting the colors to get the best result.

Working with color passes, which are independent images that reflect various components of the final composite, is one of Nuke’s key capabilities. By modifying the distinct elements that make up the composite, such as shadows, highlights, and reflections, color passes can be utilized to produce a final image that is more polished and realistic. Artists can have more control over the final image and make changes to specific elements without altering the composite by dividing these components into independent passes. In this approach, color passes to enhance the final product’s overall quality while enabling more effective and efficient compositing procedures.

To begin with, we had given a .exr image, which had all the element information such as shadows, highlights, and reflections. We had to manipulate it and color grade the truck to match and merge the truck along with the respective background.

Following to this, I manipulated the passes according to what is needed, which you can see below.

Here is an another example which was obtained with the help of manipulating the passes. I started by manipulating the Specular passes of the car, which helped in matching the tone of the car to that of the background. Specular plays a crucial role in image pass manipulating. It helps in manipulating the Luminance pass of the car. Following to this, I manipulated the diffuse pass. This was according to the ratio needed for the car merging with the background and softing the light which bounces off the car.

After this step, I matched the color of the car by using the color grading method, in which we match the color according to that of the background. This step helped me a lot in getting the final touch for merging it with the background.