Graph: Provides two options to set how the adjustable graphs in the Chroma and Luma controls are used to fine-tune a key:
Scrub Boxes: Select to limit the Chroma and Luma controls to adjusting softness (edge transparency) in the matte you’re creating. In this mode, you can’t manually adjust tolerance (core transparency), which is determined by the Green Screen Keyer effect’s automatic sampling, plus any Sample Color rectangles you’ve added in the viewer. (To increase matte tolerance, add more Sample Color rectangles or adjust the Strength slider.)
Manual: Select to use the Chroma and Luma controls to adjust the softness (edge transparency) and tolerance (core transparency) in the matte you’re creating. Make sure the Strength slider is set to a value greater than 0% before you switch to Manual mode; otherwise the Chroma and Luma controls are disabled. When you switch to Manual mode, the Refine Key tools and Strength slider become disabled, but samples you’ve made with those controls continue to contribute to the matte.
Important: When you switch to Manual mode, it’s best not to switch back to Scrub Boxes mode. For best results, begin keying an image using the Sample Color and Edges tools in Scrub Boxes mode. Switch to Manual mode afterward if you feel it’s necessary to refine your matte using the Chroma and Luma controls. However, if you switch back to Scrub Boxes mode, you may experience unexpected combinations of additionally sampled and keyframed values that might be difficult to control.
Chroma: Drag the two graphs in this color wheel control to adjust the isolated range of hue and saturation that help define the keyed matte. The selected mode governs which graphs in the color wheel are adjustable. The outer graph controls the softness (edge transparency) of the matte you’re creating, and can be adjusted in either Scrub Boxes or Manual mode. The inner graph controls tolerance (core transparency), and is only adjustable when in Manual mode. Drag any side of either graph to expand or contract the graph’s border, which adds to or subtracts from the range of hue and saturation contributing to the key. In Manual mode, you can also drag inside the tolerance graph to adjust its overall position in the color wheel. To the left of the color wheel, a small graph displays the slope of chroma rolloff, the relative softness of matte edges in regions most affected by the Chroma control. Dragging the Chroma Rolloff slider (described below) modifies the shape of this slope.
Tip: It’s possible to zoom in to and pan around the Chroma control to more precisely adjust the graphs. To zoom in to the Chroma control, move the pointer over the color wheel and, holding down the Z key, drag to the left to zoom out or to the right to zoom in. To pan in the Chroma control, hold down the H key and drag in the color wheel in the direction you want to move it. To reset the zoom and recenter the Chroma control, move the pointer over the Chroma control and press Shift-Z.
Luma: Drag the adjustable handles in this grayscale gradient to modify the isolated range of the luma channel (the range of brightness and darkness) that also helps define the keyed matte. The upper handles (which appear only in Manual mode) adjust the tolerance (core transparency) of the luma channel’s contribution to the key. The lower handles adjust the softness (edge transparency) of the luma channel’s contribution to the key. The Graph mode governs which handles are adjustable. In Scrub Boxes mode, you can adjust only the lower softness handles, which modify the range of brightness and darkness affecting the edge transparency of the matte. In Manual mode, you can also adjust the upper tolerance handles, which modify core transparency within the luma channel of the matte. By default, the slope of the left and right sides of the Luma graph has a slight “S” curve. You can modify the shape of the curve by adjusting the Luma Rolloff slider (described below).
Note: The luma softness handles may extend past the outer boundaries of the Luma control. This is due to the floating-point precision of the Green Screen Keyer effect and is expected. To reveal out-of-bounds handles and then move them, drag the slope line of the Luma graph.
Chroma Rolloff: Use this slider to adjust the linearity of the chroma rolloff slope (displayed in the small graph to the left of the Chroma control). Chroma rolloff modifies the softness of the matte around the edges of regions that are affected most by the Chroma control. Lowering this value makes the slope of the graph more linear, which softens the edges of the matte. Raising this value makes the slope of the graph steeper, which sharpens the edges of the matte.
Luma Rolloff: Use this slider to adjust the linearity of the luma rolloff slope (the ends of the bell-shaped luma curve displayed in the Luma control). Luma rolloff modifies the softness of the matte around the edges of regions that are affected most by the Luma control. Lowering this value makes the slope between the upper and lower handles in the Luma control more linear, which increases edge softness in the matte. Raising this value makes the slope steeper, sharpening the edges of the matte and making them more abrupt.
Fix Video: Select this checkbox to apply subpixel smoothing to the chroma components of the image, reducing the jagged edges that result from keying compressed media using 4:2:0, 4:1:1, or 4:2:2 chroma subsampling. Although selected by default, this checkbox can be deselected if subpixel smoothing degrades the quality of your keys.