Chroma and luma keying – matte control

Click on the button Matte Control to set the initial keying parameters. It is done with the Show Alpha Matte function which, when enabled, shows a mask’s window in black and white. Parts of the mask’s image for which the colors are closer to white will be opaque, and those closer to the dark – transparent.

A view after clicking on the Show Alpha Matte icon.

The expected result is getting a black color of the mask’s background as perfect as possible. In order to achieve it, you have to move the markers on the Black/White slider up until you get as uniform distribution of the black color on the mask’s background as you can.

A view after the Black level correction

Moving the slider to the extreme positions will make the remaining objects lose their properties becoming opaque. Therefore, you have to carefully balance the extent to which you use this function, in order to reach a point where there are still some slight but noticeable differences in the distribution of the black background. The next step is to obtain a uniform distribution of white color on the objects that are to remain completely opaque. This non-uniformity may result from the fact that some of the object’s colors may have color components close to the keyed color. In this case, you can make adjustments using the White slider’s marker.

You can obtain a perfect distribution of a white color on the object by moving the slider towards the maximum value on the left.

A view after the White level correction.

In many cases, the option of White level setting is used together with the Black option, in order to obtain the most efficient settings possible of the black background – without losses in white objects and vice versa.