Use the video keyer

Introduction

The quality of the produced key is highly dependent on:

• the green screen

• the lighting

• the camera

• the position and clothing of the talents

Learn more about how to create a good keying setup

Key video

The video keyer is an easy-to-set-up real-time chroma keyer that you can use to key your video input.

1. Double-check that:

   1. the camera system setup matches the physical camera

   2. the camera system is routed to the correct machine

2. Go to PRODUCTION > Adjust > Video Keyer

3. Select the camera system

4. Click "Enable Video Keyer"

5. Position a talent or a stand-in person on the stage, or else use a dummy model with hair, as well as a water bottle to set the transparency

6. Click "Initialize key" 
   Director grabs one image of the video feed.

   1. Draw on the image to select which colors are background and should be keyed out
      These are typically the flat green values - do not select the dark greens on the floor if you wish to get contact shadows.

      • It usually only needs a couple of strokes

      • If you want to recapture the image, just click "Capture new frame"

      • To delete all strokes use the "Clear" button

   2. Click "Initialize"

   3. Select "Send key to video output" to examine the result

   4. Refine the initial key by selecting more colors. Keep monitoring the results and repeat several times where needed

   5. Click "Close" when you are happy with the initial key

7. Refine the parameters to improve the key

   • Zoom in tight on the head of the model, and adjust the focus so that the hair is clearly shown. Then zoom back out again without adjusting focus

Don't forget to turn off "Send key to video output" when you are happy with your key.

How to show the alpha channel in the Editor

In the Editor

1. Click the "Utilities" tab

2. Click Input video > Raw

   1. Click "View"

      1. Turn on Alpha

      2. Turn off the Red, Green and Blue channels

Select Keyer Model

There are 2 keyer models available:

• Chroma-PX1: legacy keyer present in Pixotope 1.5

• Chroma-PX2 (default): new keyer using a more advanced color model with more precise color extraction and sharper alpha mask

With "Automatic Clean Plate Generation" enabled and "Add Luma Key" being used, the reference is automatically generated from the locally closest backing color.

Refine

Remove Background

Increases the domain of the selected background colors.

Adjust Foreground

Increases the domain of the foreground.

Maintaining a good distance between the Background and Foreground sliders will ensure a good soft edge on the key.

Add luma key

Adds to the key based on the pixel luma value.

This can help to fill in regions of a soft foreground region.

Adjust Key Color Intensities

Red, Green and Blue

Allow adjustment of key intensity based on RGB pixel value to make red “repel” or be “insensitive” to keying, for example.

This is especially useful for preserving colors that are close to green, e.g. yellows. To preserve cyans, you have to reduce the blue intensity slightly.

Mask adjustments

To adjust the alpha mask from the internal keyer.

Gamma

Controls the gamma correction of the key.

Gain

Controls the gain of the key. 1 is the default and larger values increase the gain.

Erode

Controls the tightness of the alpha mask. A higher value results in a more eroded mask. This is a sub-pixel erode control.

Detail Enhancement

Controls the strength of the effect. Increasing the level will help to include more details in the soft edges.

Luma adjustments

Edge Luma Correction

Controls luma range on despilled area - this blends back the original luminance value of the edge pixels, rather than using the luminance of the background pixel - carefully controlled, this will blend the edges in better to the background.

Shadows

The Shadow controls allow you to add shadows that exist on the evenly lit backdrop.

Add shadows

Controls the intensity of the key in the shadow areas. A value of zero gives no shadows - set a subtle value to get believable soft shadows.

Adjust contrast

Adjusts the depth of the shadows that are generated. The default is 100%.

Despill

The Despill controls allow you to vary the background color removal from the foreground, adjust the foreground color range that is despilled, as well as allowing you to adjust the hue for the areas containing the spill.

Strength

Controls the strength of the effect. The default is 100% with full despill. Reduce the value to see if other colors than the background are being despilled as well.

Cutoff

Controls the range of colors that are despilled by color distance from the original background picked color. For example, yellow and light blue may also be despilled by default. Adjusting the Cutoff can exclude both colors from the despill range and so preserve the original foreground colors.

Hue

Changes the hue of the despilled area.

Hue changes the hue angle of the range of the despilled colors. Use with care to preserve skin tones - it is generally better to use the Cutoff control rather than the Hue to preserve the original foreground colors.

More details about Pixotope's Chroma Keyer.