q - i have a pd - 100 cam (sony) im filming actors behinde a greenscreen dressed in black

after i cupture the footaged to the computer whith simple-firewire-card

the footaged recived has an affected on the black clouth

the effeced is a shadowy snow shaking fast moving affecd

how do i recive a clean black picture ?

thak you for your attention

may you be blessed