The Blue Screen Key creates transparency from true chroma blue. Use this key to key out well‑lit blue screens when creating composites.

The following Blue Screen Key settings are adjusted in the Effect Controls panel:

Threshold

Sets the levels of blue that determines transparent areas in a clip. Dragging the slider to the left increases the amount of transparency. Use the Mask Only option to view black (transparent) areas as you drag the Threshold slider.

Cutoff

Sets the opacity of nontransparent areas specified by the Threshold setting. Dragging the Cutoff slider to the right increases the opacity. Use the Mask Only option to view white (opaque) areas as you drag the Cutoff slider.

Smoothing

Specifies the amount of anti-aliasing (softening) applied to the boundary between transparent and opaque regions. Choose None to produce sharp edges, with no anti-aliasing. This option is useful when you want to preserve sharp lines, such as those in titles. Choose Low or High to produce different amounts of smoothing.

Mask Only

Displays only the clip’s alpha channel. Black represents transparent areas, white represents opaque areas, and gray represents partially transparent areas.

Subject is photographed against blue background (left). Blue Screen Key effect is applied (right) to superimpose subject over underlying track.