Use the List and Gain fields with the Input Level controls, in the 2D Histogram node in the schematic, to set the range of luminance values in the matte. You can darken black areas of the matte or remove grey from white areas of the matte.
(a) Minimum Input level (b) Maximum Input level
Removing Grey from the Black Areas of the Matte
The Minimum Input level sets the start of the range of luminance values. Pixels with luminance values below the Minimum Input level are mapped to black (0).
You can set the Minimum Input level by dragging the black triangle, or by setting a value in the Minimum Input Level field.
 The matte before adjusting the Input levels |
 The matte after lowering the Minimum Input level |
Removing Grey from the White Areas of the Matte
The Maximum Input level sets the end of the range of luminance values. Pixels with luminance values greater than the Maximum Input level are mapped to white (255).
You can set the Maximum Input level by dragging the white triangle, or by setting a value in the Maximum Input Level field.
 The matte before adjusting the Input levels |
 The matte after lowering the Maximum Input level |