Adding Softness

The term softness refers to the semi-transparent area of the matte that creates a smooth transition between the foreground and background image. The softness range is the range of colors that are made semi-transparent.

At the center of the range, the colors are completely transparent. As you move away from the center, colors become less transparent.

Typically you define a softness range as large as possible to remove all the blue or green from the front clip. But remember, if the range is too large, you will key out parts of the front subject.

Setting the softness is an iterative process. You start by adding too much softness, then reduce it a little, increase it again, and so, on until you get just the right amount.

When you cannot increase softness without losing edge definition or making holes in the matte, use other techniques such as color correction or matte curves to finish the key. These techniques are described in subsequent sections.

Note: The multiple undos available in combustion are useful when you are experimenting with different settings. Press Ctrl+Z to undo a change. You can also click the Reset button to reset the Key controls to the default values.

To adjust softness:

1. In the Keyer, click Key to access the softness controls.

Note: Enable Feedback so that you can see the effect of the softness adjustments in the viewport as you work.

2. Do one of the following:
• Set the Softness Offset. This changes the softness range by the same amount for every channel.
  
• Click the Add Softness picker and drag the picker in the area that needs softening. The softness range expands to include the colors that you sampled. Ctrl-drag to sample a rectangular area.
• Click the Remove Softness picker and drag the picker over areas that are too soft. The softness range shrinks to exclude the values that you sampled.
• Set the softness by channel. You can set the softness on either side of the range by dragging the yellow line in the channel color bar.
• Plot a point in the image and adjust the softness to include or exclude the value of that pixel. See Using the Plot Tool.

Note: For a color to be transparent, all of its color channels must fall inside the softness range. For example, if you are using the RGB keying mode, only pixels whose red, green, and blue values are all within the softness range will be transparent. If one of the pixel's channels is outside the softness range, the pixel will be opaque.