The Luminance Threshold effect generates a matte by thresholding the luminance of an image. This works well with bitmap images that have many shades of colours. A pure vector image with flat colors could use a color override to isolate areas.
Thresholding is a method to segment or isolate certain zones in an image. This effect will isolate areas based on the image's luminance. Thresholding is used within the Bloom effect—see Bloom Node.
Connection
The Luminance-Threshold node takes an image of any type as its input and outputs an image in which pixels that do not pass the threshold are filtered out and the remaining pixels are softened and have their gamma adjusted.
Optionally, it can also be connected to a matte image. In this case, only the parts of the input image that intersect with the matte will be affected by the effect.
Layer Properties
| Parameter | Description |
|---|---|
| Enable/Disable |
Allows you to enable or disable the node. When disabled, a node has no visible effect on the rendered image, nor on the preview in the Camera, |
| Colour Swatch |
Sets the colour of the layer in the Timeline view |
| Name |
The name of the node as it appears in the Node View and the Timeline view. Each node must have a name that is unique to its containing group. |
| Threshold |
Controls how much of the dark value to clamp off. A high value will keep only the bright areas of your image.
|
| Soften Colours |
Brings back the entire spectrum of luminance in areas defined by the threshold to avoid having only bright values.
|
| Gamma Correction |
Multiplies the gamma value to make the area brighter or darker. A value of 1 keeps the gamma the same as the original image. You can use the gamma modification on the whole image if you use a threshold of 0 for example.
|
| Output Greyscale Matte |
Allows you output an image in levels of grey. This can be used in combination with a Blending or Cutter node, or other effects that use greyscale mattes. |
| Invert Matte |
Inverts the matte used to generate the effect. By default, the effect is applied to the opaque areas of the matte drawing. When this option is enabled, the effect is applied to the transparent areas of the matte instead. |
