Re: Shooting subject on a black background
 

@jody when you evenly light a 3D object like a face, it makes it "flat" because it removes the shadows that help us see the 3D surface (eye sockets, nose, lips ...). If one side is brighter than the other, it leaves some shadows. The brighter of the two is from the Key light and the other from the Fill. The dimmer you make the fill, the more shadow you get and typically more dramatic feel. If the side facing the camera is the brighter side made by the Key, it's called shooting "On Key". If the side facing the camera is the fill side, it's called shooting "Off Key".

In my example, I am shooting On Key. Look at the cheeks. Her right cheek is dark vs her left. You also see nose shadow on the nasal labial area created by the Key and not "erased" by the opposing fill.

There's nothing wrong with shooting flat. Here's a great set of Black Void examples from interviews with documentary producers:
Capturing Reality: The Art of Documentary

Re: Shooting subject on a black background
 

I'd suggest you raise the key light higher, so that shadows are cast downward rather than sideways.

Bear in mind that your subject may look differently in this light than you do, this typically has a lot to do with the depth of the eye sockets. My starting point for key placement is 45-deg to the sided and 45-deg up, which is then adjusted depending on those shadows, especially to the off-key side of the nose and off-key eye socket.

Re: Shooting subject on a black background
 

@Robyn ... tap tap tap.... what happened here? How'd it come out? How about some pics?