Set up your Key Light:
The most important thing in key lighting technique is how you setup your source or key light. You should place the light in a way that your actor and light are making an angle of 45 degrees. Make sure it has been placed at proper height otherwise you won’t be able to cover shadows even with the filler. Similarly, the beam should brighten a little bit of background as well otherwise your subject will not be significant.
Use fill light wisely:
As mentioned earlier, the beam from source light will create a shadow on the nose or neck of the actor so you will need filler light which is less bright then the key light. Its purpose is just to throw a beam on the face and cover the shady spots. Fill light is always adjusted in front of the actor and just next to the camera lens.
Set up the back light:
To save your subject from being dead, you will throw light on his or her shoulder from the backside. Fixing a light at a 45 degrees angle will separate your character from the background. However, it should not be too radiant otherwise it will kill your source light and fill light.
Adjust your lights:
Now, when you have fixed your lights at proper places, it’s time to create a point where they meet. Make sure they are not crossing each other as there will be a possibility of uneven lighting then. The best and the easiest way to check your lighting is to ensure meeting of all the beams on a point where your character is standing.
Make changes according to scene requirement:
You must remember that only the position of lights is fixed and you can adjust their intensity according to requirement of the scene. If you want hard lighting then you will use small lights as their beam is not wide.