You
            can limit the keyed area by drawing a crop box on the image.Typically, this feature
               is enabled before starting the key to avoid unnecessary processing while
               working at high resolution.
         To draw the crop box:
         
         
            - In the Keyer, click Setup.
               The Setup menu appears.
                
- Enable Draw Crop.
            
- Draw the crop box by selecting a point
               on the image and dragging the cursor diagonally.
            
- Click Crop to enable the crop box.
               Keying operations now
                  affect only the cropped area.
                NoteWhen the clip is
                     processed with the crop box enabled, only the cropped area is keyed.
                     Remember to disable the crop box if you want to apply the key to
                     the entire frame.