Lighting ratio

The next thing that you will need to learn before you actually start using the studio lighting is to understand lighting ratio. So what it is? It is the difference between the main light and the fill.

If your main light were twice as bright as your fill, the ratio would be 2:1. Thinking about exposure factors, a factor of 2 is equal to one stop of exposure, and if you increase your exposure by one stop, you are allowing in twice the amount of light.

Thus, a 2:1 ratio would mean that there is a one- stop difference between the lights. A 3:1 ratio would be a stop and a half difference, and 4:1 would be a two stop difference.

So how do we deal with this ratios? Its actually just either multiply or divide by 2. This means if you want to determine how much exposure difference there is in a ratio of 5:1, you would divide 5 by 2. The answer would be 2 1/2 stops. If you had a scene with 2 1/2 stop difference between the lights and you wanted to determine the ratio, you would multiply 2 1/2 by 2 and would give you 5 for a 5:1 ratio.

The table above is just some of the common lighting ratios which you use for different situation.

So after I've been mentioning main light and fill light, do you really understand what does it mean? Main light is actually the key light that illuminates your subject. It has the most power that is why it is called the main light. As for the fill light, it just fills up the light on your subject. It cannot be more powerful than the key light or else this fill light will become the main light in the end.