# Chroma Keying and Working with Green Screens

The Modular Keyer is a schematic environment, like ConnectFX, that is designed specifically keying. Within the Modular Keyer, you can choose different Start Modes or presets, which generate node schematics adapted to the different keys you want to pull, such as 3D keys, chroma keys, etc.

When you start the Modular Keyer for the first time, Smoke builds a default schematic that includes the Master Keyer node, in addition to a number of other nodes, that all work well together to create and refine a basic key. This is the Master Keyer Start Mode.

Within the Modular Keyer, the keyers are represented as processing pipelines, which are collections of interconnected nodes. As you perform keying tasks in the Modular Keyer, you navigate from node to node to accomplish the final key, displayed in the Result node.

As a general example, you could proceed as follows:

- Key out the selected colour in the Keyer node;
- Adjust your blacks and your whites in the 2D Histogram node;
- Refine your matte in the Matte Edge node;
- Mask out troublesome areas of your matte in the GMask node;
- Perform colour correction of the front clip in the Master Keyer node or the Colour Curves node;
- View the result in the Result node.

Because it is node-based, you have a lot of flexibility with the Modular Keyer. You can:

- Choose a different Start Mode to start with a different default keying pipeline. Options are:
  - Channel Keyer
  - HLS Keyer
  - Luminance Keyer
  - Master Keyer
  - RGB Keyer
  - RGBCMYL Keyer
  - YUV Keyer

  ImportantWhen you select another Start Mode, any work in progress will be lost and the selected keyer is loaded with the default settings.
- Add other effects nodes from the node bin to further refine your key.

#### Topics in this section

- Setting Up the Nodes and Media to Pull a Key
- Setting Up Viewports for Keying
- Creating and Refining a Key in the Master Keyer
- Creating a Key by Extracting a Single Colour with the Channel Keyer
- Creating a Key by Extracting a Range of Colours with the HLS, YUV, RGB and RGBCMYL Keyers
- Creating a Key by Setting the Luminance
- Refining Your Key
- Resetting Your Key
- Rendering Your Key