Multiple lights mean multiple shadows!
Shadows are a part of life and are not to be feared in motion pictures. Skillfully placed, they add depth and texture to images and help turn an essentially flat representation of people and objects into something approximate to the human experience.
According to the script, there will be times when varying grades of shadows are appropriate and times when they will not. Those are questions of taste, but your taste needs to be backed up by a level of technical\mechanical competency. So, listen up, fledgling cinematographers…
When faced with distracting, inappropriate or competing shadows on set, trace each one back to its source. Having done so, you have four basic choices in how to control them, contingent upon the dramatic effect you’re trying to achieve.
Extinguish the offending source.
Change the position of the offending source.
Flag off the offending source from the subject or item that’s casting the shadow.
Use diffusion to increase the size of the offending source, softening it to the point where the effect of the shadow becomes negligible.
You might also change the frame or restage the blocking of the actors, but those are the last remedies you should call on to solve such a simple problem, resorting to them only after affirming you’ll have a new line of work waiting for you in another state tomorrow morning.
As always, keep it simple. The fewer lights you use to get the job done means the fewer unwanted shadows you’ll have. Your photography will be better and your director with thank you for that.
So will your grip and electric departments!