The scene effects panel has controls for antialiasing, depth of field, and motion blur.
A value of 1.0 is physically correct. Setting the value to 0 removes this feature from the rendering pipeline.
59.94i Rendering Settings
Rendering 59.94i interlaced video is very demanding, as the entire 3D scene has to be rendered 59.94 times per second. When using video backgrounds, however, there is usually not a need for antialiasing or motion blur.
Suggested 59.94i Rendering Settings:
Depth of Field scale: 1
Motion Blur Scale: 0
If the frame drop light is still going off, decrease the depth of field scale. The defocus algorithm used for depth of field is adaptive, and requires more rendering time the larger the radius of the defocus.
Click the colored swatch next to Background Color to adjust the background color that will appear where the foreground is keyed out and the CG background ends.