Here is a brief guide to setting up four point lighting for your digital video production.
Four Point Lighting for Video
Four point lighting is at the root of most lighting set ups for digital video or motion film. Three point lighting is often discussed, especially as it relates to video interview set ups. Three point lighting is a very common way of presenting lights, and in a sense four point lighting stems from similar principles.
Though the names can be semantics, four point lighting is often considered to have slightly different purposes than three point lighting and the exact positions and realities of the light you do use may be somewhat different. Here is a brief guide to four point lighting and how to employ it in your digital video set up.
Four Point Lighting vs. Three Point Lighting
What four point lighting and three point lighting share in common are their basic lighting triangle. All three of them will employ a main light, called the key. The key light will come in one one side and act as the main light source. The key light will be used to get the most viewable side of the subjects face, unless you want it to be consumed by shadow.
The opposing light that also comes from the front will be the fill. In three point lighting this is often done by a white card so that there is simply a diffused light coming on the other side of the subjects face lightly. This is done just to see the skin tone of the subject and not to get dramatic definition.
Four point lighting will be a little looser with this, mainly because four point lighting is more responsive to the needs of dramatic narrative scene. Both three point lighting and four point lighting will employ a back light to hit the subject's head. The backlight in four point lighting is often called the edge light, and it is usually brought up far above the subject's head so that it will peer down on them. You may also want to bring back the edge light away from the subject's head in a four point lighting set up.
The main light that differentiates a proper four point lighting set up and a three point lighting set up is the background light. The background light is intended to give depth to the image by putting some mixture of light and shadow on the wall behind the subject or subjects. Make sure that there is several feet between the subject and the wall. Give the light that you are using an intermediary to alter the beam. A conventional use of this process is to have the background light from the four point lighting set up come through a window so that a graphic of the window pane will be blasted onto the wall behind the subject. You can also try to use different nets, gels, or scrims to alter the background image.
Freedom for Lighting
Four point lighting essentially sets up this square, yet it tries to remain free and responsive to movement and changes. Four point lighting is supposed to be the practical basis for most narrative film lighting, so you have the options to change it. The major changes in four point lighting come from utilizing excess light in the form of bounce cards, reflectors, or different diffusing silks.
The opposite can be the employ of cutters or negative fill to get rid of extra light. There is no set rule for how four point lighting must be set up, so you are going to have to adjust and re-adjust until you find what fits. Try dealing with light diffusers on both the key and fill in the four point lighting set up so that you have more freedom to move them around the set.