If you look at any commercial portrait, you will notice that there is no ambiguity between the object of interest, the sitter, and the background, usually a large sheet of textured, colored paper that acts as a spacial field. The subject is clear, we are looking at a picture of "so and so" and not knowing who "so and so" is, the lack of context in the background makes the portrait all the more anonymous. Notice how William Wegman uses a blue background to enhance his two sitters. Visually cool colors such as blue will recede and warm colors come forward. There is no ambiguity as to the center of interest in the photo.
William Wegman, "Cinderella" 1994
As a photo journalist documenting working conditions in Júarez, Mexico, Julián Cardona does not have the luxury of a studio where he can control background and lighting. He uses flash, available lighting, depth of field and strong composition to isolate the center of interest, the young worker in the factory. Because the depth of field blurs the men in the background, the merging is less obvious and doesn't interfere with our subject. The blue machines form frames.
Julián Cardona, "A Young Girl at Work" 1998
Symmetry, balance, and simplicity all work together to communicate the idea in Spanish artist Chema Madoz formalist images that remind us of the French Surrealists.
Chema Madoz, Untitled, 1992
Unlike human perception, the camera sees everything. A common photographic problem is how to draw the viewers attention to the center of interest. The three photos above are different approaches however they all successfully solve the problem. Create a set of images the clearly show separation of the figure (center of interest) and the ground (background).
Use a minimum of one roll of film and compose images that isolate the following objects:
A single tree
A single building, house, or barn etc.
A human figure - posed and clothed (not an action shot)
Any other object of your choice