Learn easy ways to troubleshoot and fix problems with your three point lighting.
Using Three Point Lighting
Three point lighting is one of the fundamental lighting set ups that we have in film production, most commonly used on people's faces. This method casts a general set of lights around a person's head and body as to try to make them look as clean and nice as possible. The basic set up of three point lighting is known by many people, but often times it is difficult to identify and location problems with what you have created.
Key Light, Fill Light, and Back Light
One of the most common issues with three point lighting is if the lights are placed in the wrong locations or are somehow reversed. When you have a subject looking slightly to one side you are going to put the key light on their face from that side. The fill light will go on the long side of their face, that way the softer light will be located on the side of their face that is seen more. This side of the face is the direction that they are not looking in, so it is actually the one that dominates the image. The backlight is to shine on the back of them so as to cut them out from the background and make them pop a little more. The backlight tends to be on the same side as the fill light so that it runs diagonal to the key light. This is the basic set up and going away from this can cause a number of issues. If the position of the subject is maintained and the key and fill light is switch you can get awkward shadows on the nose and middle of the face. The eyes can appear out of line and you can bring out blemishes. Make sure that the positions are in the correct place and if you want to switch them make sure that your purpose actually motivates it.
Often times you can get a hot spot on the lens from the backlight. This usually means that the backlight is both not in the right height position and that it has not been rotated correctly. Begin by tilting the light down so that it hits the back of the subject's head and not above it. Then rotate it slightly away from the subject to lower the intensity. This process of rotation should be the first troubleshooting idea for lowering a backlight that is too intense. This is especially true if they are getting a bright halo on their head that is taking away from the fill light on their face.
Soften it Up
If the key light is getting to bright on their face, making them squint, or causing dramatic shadows then the first thing you should do is add a silk screen and not a scrim. A scrim will lower the intensity, but it will remain dramatic. Try putting a silk up to troubleshoot this issue first, then try to use a reflector and turn the light away from the subject. That way you will only get diffused and reflected light on the subject's face. This will help the three point lighting set up be a little more practical for tight locations.
The eye light is standard to get a sparkle in someone's eyes, but this can be difficult to align without a fourth light. Instead of troubleshooting a lack of eye light with a fourth light simply try small movements of the key light and raising it up higher for a tilt down. If it is already diffused then this process is going to be easier. If you are dealing with glasses you are going to have to raise it up pretty high to avoid glare anyway, but if at all possible have the subject remove their glass. If they have sun glasses then just heavily diffuse the key.