Production: Working with the Foreground
During production, you will be constantly trying to achieve the most dynamic framing possible. There are many ways to transform that standard shot into something interesting. One such technique is to use foreground elements to add depth to the space.
One reason to employ foreground elements is to enhance the frame. Consider placing an object quite close to the lens. This object will inherently be completely soft if your subject is in focus. So, it really doesn't matter what you use as long as the general shape is as desired. This silhouette will give you the sense that the scene is being observed from far away. The partial obstruction implies that we are hiding behind something and watching a moment we are not supposed to see. This can work in a number of different scenes whether they be intimate or sinister.
You are shooting a scene in which a character leaves the apartment and forgets their keys. Here, you can give the audience all the information they need in one shot. Though yes, you can shoot the character leaving followed by an insert of their keys, why not create a frame that will enhance the aggravation? Try to place the camera where the keys are in the foreground and the door is in the background. The trick is being able to see both without obstructing the door. It may take some millimetric adjustments to find just the right spot. Of course, now you have an issue of focus. The door will never be in focus at the same time as the keys. A well timed rack will amplify the effect and leave the audience thinking "They're right there!"
A more difficult use of foreground elements is when you want to use characters on different planes. Though an over the shoulder shot is a nice example of this, we will be more concerned with a shot in which you see both characters faces. Let's say you have a woman looking out a window. Ten feet behind her is a man looking at her. You set the camera up outside the window looking in. Now, you have the woman in the foreground with her gaze transfixed on something outside, and a man in the background. The question now becomes: what do you focus on?
The answer is in the content of the scene. If both characters are exchanging dialogue, you can consider racking back and forth between them. This can get complicated if the timing is unpredictable. You may also consider leaving the focus on the woman even as the man is speaking. Perhaps the woman's reactions are more important than the man's words. So now you are using the multidimensional frame to tell the audience that this character is important in this scene, so much that we do not even really need to see the man clearly.
Using foreground elements can help you take command over the screen. Not only can you create more interesting shots, but you can amplify the meaning that you are trying to convey.