Lets face it cameras are becoming more and more sensitive. We no longer need the kinds of light levels that we once used to need. So why is lighting still so incredibly important. Why do we light?
Starting at a most basic level, there are two reason for lighting a scene. The first and perhaps most obvious is to add enough light for the camera to be able to “see” the scene, to get an adequate exposure. The other reason we need to light, the creative reason why we need to light is to create shadows.
It is not the light in a scene that makes it look interesting, it is the shadows. It is the contrast between light and dark that makes an image intriguing to our eyes and brain. Shadows add depth, they can be used to add a sense of mystery or draw the viewers gaze to the brighter parts of the scene. Without shadows, without contrast most scenes will be visually uninteresting.
Take a typical daytime TV show. Perhaps a game show. Look at how it has been lit. In almost every case it will have been lit to provide a uniform and even light level across the entire set. It will be bright so that the cameras can use a reasonable aperture for a deep depth of field. This helps the camera operators keep everything focus. The flat, uniform light means that the stars or contestants can go anywhere in the set and still look OK. This is lighting for exposure, where the prime driver is a well exposed image. The majority of the light will be coming from the camera side of the set or from above the set with all the light flooding inwards into the set.
Then look at a well made movie. The lighting will be very different. Often the main source of light will be coming from the side or possibly even the rear of the scene. This creates dark shadows on the opposite side of the set/scene. It will cast deep shadows across faces and it’s often the shadow side of a face that is more interesting than the bright side.
A lot of movie lighting is done from diagonally opposite the cameras to create very deep shadows on faces and to keep the background of the shot dark. If, as is typical in TV production your lights are placed where the cameras are and pointed into the set, then all the light will go into set and illuminate the set from front to back. If your lights are towards the side or rear of the set and are facing towards the cameras the light will be falling out of and away from the set rather than into the set. This means you can then keep the rear of the set dark much more easily. Having the main light source opposite the camera is also why you see far more lens flare effects in movies compared to TV as the light is often shining into the camera lens.
If you are shooting a night scene and you want to get nice clean pictures from your camera then contrast becomes key. When we think of what things look like at night we automatically think “dark”. But cameras don’t like darkness, they like light, even the modern super sensitive cameras still work better when there is a a decent amount of light. So one of the keys to a great looking night scene is to light the foreground faces of your cast well but keep the background very dark. You expose the camera for the bright foreground (which means you should not have any noise problems) and then rely on the fact that the background is dark to make the scene look like a night scene. Again the reason to light is for better shadows, to make the darker parts of the scene appear very dark relative to the foreground and a high level of contrast will make it look like night. Consider a bright moonlit night, faces will be bright compared to everything else.
So in cinematography, very often the reason to add light is to create shadows and contrast rather than to simply raise the overall light level. To make this easier we need to think about reflections and how the light that we are adding will bounce around the set and reduce the high contrast that we may be seeking. For this reason most film studios have black walls and floors. It’s amazing how much light bounces of the floor. Black drapes can be hung against walls or placed on the floor as “negative fill” to suck up any stray light. Black flags can be used to cut and control any undesired light output from your lamps and a black drape or flag placed on the shadow side of a face will often help increase the contrast across that face by reducing stray reflections. Flags are as important as lights if you want to control contrast. Barn doors on a lamp help, but if you really want to precisely cut a beam of light the flag will need to be closer to the subject.
I think most people that are new to lighting focus too much on the lights themselves and don’t spend enough time learning how to modify light with diffusers, reflectors and flags. Good video lights are expensive, but if you can’t control and modify that light you may as well just by a DIY floodlight from your local hardware store.
Also consider using fewer lights. More is not necessarily better. The more lights you add the more light sources you need to control and flag. The more light you will have bouncing around your set reducing your contrast and spilling into your otherwise nice shadows. More lights means multiple shadows going in different directions that you will have to deal with. Instead of using lots of lights be more careful about where you place the lights you do have, make better use of diffusion perhaps by bringing it closer to your subject to get more light wrap around rather than using separate key and fill lights.