If you have been in a class with me you are full aware of my thought process when setting up my lighting. I am always, yes always, looking at light quantity, light quality and light direction, especially when on location, these three items are crucial in my process to create an image that makes sense and works.
Let us go through them one by one. First, light quantity. How much light is there? This really comes down to exposure. Do you have enough to create a printable exposure (we will talk about that later)? Do you need to add or remove light from the scene? Second is light quality. What is the hardness of the light? This will help you decide what modifier to use and how far to place the light from your subject. Finally, is light direction. Where is the light coming from? To make an image believable when augmenting existing light, I believe it needs to be justified, meaning, the light direction needs to make sense. You do not want light on the subject from left to right when the light on the background is right to left.
Take the following image. My subject wanted an image with his car looking like James Bond. We found a location that was clean yet had some design interest that would not take away from the subject. By asking myself the same questions we discussed, I am able to light my subject and create a successful image. The building behind him was in direct sun, he was in he shade of another building. I knew the quantity on the building was f/16 due to the sunny 16 rule and my meter told me he was f/5.6. That difference in light quantity allowed me to address the first question- Add or remove light. Below are images without the light exposing for him and the building. You will notice that the dynamic range was too far apart. Even if the light values were closer, I still would have added light to have the same quality of light. Remember I am looking at all three. The easier thing is to add light to my subject to make him f/16 rather than try to take light away from the building. I used a Profoto D1 head with an external power pack to do that.
Second, light quality. The direct sunlight produces a very hard light quality. The shadow edges are crisp. This answered my second question. I need a small light source to mimic the quality of sun light. I used a small parabolic reflector and had the light as far away as I could get it and still maintain the quantity of f/16 that I needed. Finally, light direction. This was easy in this instance. I placed the light high on a stand coming from left to right, the same direction as the sun. Now I am ready to create.
I believe the finished images looks like natural sunlight, an image I could not have completed successfully without walking through those questions and steps. Happy creating, Cris.