The key is the main light on the face. A window gives a big, soft key for free.

Use it when. Put the actor beside the window, not facing it and not with their back to it. Light from 45 degrees to one side shapes the face.

On the phone. Daylight changes by the hour. Shoot the whole scene in one sitting, or block the window and use lamps.

Key lights the face. Fill, opposite and weaker, softens the shadow. Back light, behind, separates the head from the wall.

Use it when. The standard setup for a single. With one LED panel, use it as key and a white wall or a sheet as fill.

On the phone. A cheap LED panel and a white bedsheet on a chair is a real two-light setup.

A small light makes hard shadows with sharp edges. A big light, or a small one through a sheet, makes soft shadows.

Use it when. Soft for faces and dialogue. Hard for threat, night, interrogation, and shafts of light through a door.

On the phone. A phone sensor struggles with hard contrast. Soft light hides its limits.

A lamp that appears in the shot: a desk lamp, a torch, a screen. It explains where the light comes from.

Use it when. Night scenes. Put a practical in the wide, then light the close-ups from the same side so it looks like the lamp did it.

On the phone. Swap the bulb for a brighter one and dim it with a cloth. The lamp itself is often too dim to light the face.

How much brighter the key side of the face is than the fill side. Low ratio is flat and friendly. High ratio is dramatic.

Use it when. Comedy and daytime: low ratio. Suspense and night: high ratio.

On the phone. Check the shadow side on the phone screen. If it turns to black mush, add fill.

One key placed between the two actors, on the far side of the line, lights both faces from the camera’s side.

Use it when. Any two-shot and its over-the-shoulders. Place the key once and it works for every angle on that side of the line.

On the phone. If the key is on the camera side of the line it goes flat. Keep it across the line, toward the back wall.