Here are a few tips for considering lighting moving objects in your cinematography.
Cinematorgaphy for Lighting Moving Objects
Much of the digital video lighting that people discuss for cinematography is really based around fairly stationary images, and some of it is even derived from still photography. In a real project people and objects move on a regular basis, and you need to compensate for this when you are actually lighting them for the camera. Here are some cinematography tips for lighting moving objects in your digital video or HD project.
Moving to a Stationary Position
Though it is going to seem counterinuitive to what was just said, the main attention is still on the subjects when they are still. Though they will be moving around time and space quite a bit in your film, they will still usually return to a still location when important lines or actions are taking place. When you are thinking about cinematography for lighting moving objects part of what you should be considering is how to light for a still object that the object will then move into. What this means is that you have to have the actor position themselves at their final physical location, where you will then set the lighting and even focus the camera for fine focus. You will then set marks with gaffer tape where they need to position themselves, and then rehearse the movement into the lighting position several times. The entire motion will not necessarily be perfectly lit, but you can broadly light the rest of the area in the same color temperature so it will match approximately. This is going to allow the most focused on area of the movement, the ending, to look just as sharp as if the objects were stationary the entire time.
As mentioned earlier, you are not going to be able to apply the same kind of lighting to a quickly moving object as you do with a still one. Even if you do have a perfect key, fill, and backlight on different positions in their path of movement, it will be so brief that it will not necessarily register with the audience. Instead, you can still take these four point lighting conventions and apply them to a broad lighting pattern. First, you will likely want to light the entire area broadly so that everywhere is lit to be scene. You can then apply single, or multiple, lights so that different areas are sharply lit, giving more character to the image. See where the path of motion is and make sure that is adequately lit, and then use the "backlight" principle to make sure that the background is lit and cut out from the foreground motion. The reality is that you are just going to want to get the whole place lit up so that things can be seen, but if you have enough control you can even try to go for more specific lighting such as from above, underneath, and other areas that will allow for light reflections in the movement to be more apparent.
If you are following the subjects more closely, such as a dolly backward for the camera where the characters follow the path set by the dolly, you can control the lighting much more closely. In the same way you will still need a broad lighting to fill the gaps, but from here you can try to do mobile lighting where the lights will continue to follow the path of the actors movement. This can be unrealistic in many place, and instead you can just focus on light different parts of the pathway in a fashion that was impossible for quickly moving objects.
For cinematography when lighting moving objects, you may want to try to cut up different shots as much as possible. Shorter shots will be easier to light with still lighting schemes, and when you cut them together even the smaller movements will seem to be much faster and hold more gravity. This way when you are actually filming the moving objects you can have them go much slower and then have that change character in the post-production process.