The Keying > Chroma Keyer effect
The Keying > Chroma Keyer effect is used to make pixels transparent depending on their tint and saturation.
The panel and the buttons of this effect look very similar to the ones of the effect Color > Color Eraser. That's why we will not explain each parameters in details...
Let's take for example the video sequence above with orange and red flowers. The background of this sequence is a blue-gray shutter (more or less dark blue-gray tints).
If you use the Keying > Color Keyer effect by selecting one of the dark shutter colors, it will not remove all the shutter pixels but it will remove some pixels of the flower's stalk too. (see below (1))
If you use the Keying > Color Keyer effect by selecting one of the light shutter colors, it will remove all the pixels of the shutter but it will remove the light pixels of the flower's too. (see below (2))
The results above, obtained after the use of the Keying > Color Keyer effect, are imperfect.
The Keying > Chroma Keyer effect will help us to obtain better results.
* The Tint parameter bar will make transparent the blue pixels in a wide range : light blue or dark blue will not change the result. The orange-red pixels of the flowers and the green pixels of the stalk will stay unchanged.
* The Saturation parameter bar permits to make blue pixels more or less transparent depending on their saturation. As a consequence, we will be able to make transparent all the blue-gray pixels.
Here is the result : we finally succeed to keep the pixels of the flowers visible and make the pixels of the shutter transparent.
To finish our work, we can easily add a landscape on a layer and put it behind the flowers layer. (see the timeline below)
Let's go back to our blue-screened character :
Although we used the Keying > Color Keyer effect with the our blue-screened character in the last chapter, you certainly guess that it is also possible to use the Keying > Chroma Keyer effect.
When characters are shot with blue screen, there are sometimes some undesired light effects, especially little blue reflections colorizing some part of the image (see image below on the left).
It is of course possible to remove the blue tint to these pixels by making them grey. That's the function of sliders and buttons from the Spill Removal section of the panel.