Keying


HitFilm includes several effects for keying your layers.

Keying is the term used for automatically removing parts of an image or video, usually by identifying a specific color.

Alpha brightness & contrast

The brightness and contrast of a layer's alpha channel can be adjusted to tweak the edges of a composite.

Chroma UV blur

The UV blur can be essential depending on the way your video camera stores its data.

After keying some video you may notice a pixellated 'stepping' around the edge of the key. If this occurs, add a chroma UV blur before the key itself. This will help to smooth out the edge.

Color difference key

This is the primary keying effect and is used for removing green screen and blue screen backgrounds from video and images.

If you need to key based on an arbitrary color use the Hue & RGB key.

The View matte option is a quick way to see the layer's alpha channel, making it easier to identify areas where the key needs to be cleaned up.

Erode white

The erode effect gradually removes the edge of a layer's alpha channel.

Hue & RGB key

This effect keys the layer based on a color of your choice. You can pick between using the hue or RGB values.

The View matte option is a quick way to see the layer's alpha channel, making it easier to identify areas where the key needs to be cleaned up.

Invert alpha

Inverts the layer's alpha channel.

Light wrap

You can often improve composites using light wrap, which enables light from another layer to bleed onto the keyed layer.

If you have transformed or added effects to the light wrap source layer, you will need to convert it to an embedded composite shot for the light wrap to take those changes into account.

Luminance key

This effect keys the layer based on its brightness. This can be particularly useful for sky replacement.

Matte cleaner

After keying a layer you can use the matte cleaner to tidy up the composite.

Smooth - makes the edge of the key smoother.
Feather - makes the edge of the key softer.
Choke - shrinks the edge of the key.

The View matte option is a quick way to see the layer's alpha channel, making it easier to identify areas where the key needs to be cleaned up.

Remove color matting

When using stock footage, this effect can be used to reduce dark areas in the composited element.

Most effective when used after stock has been composited using the channel swapper.

Set matte

Enables you to use channels from another layer on the current layer. This can be particularly useful if you want to use the alpha channel from another layer.

Spill removal

When working with green screen and blue screen you can sometimes find slight color fringing around the edge of a key after the screen has been removed. The spill removal effect removes or reduces this color fringing.