Contrast

DSC_0140, originally uploaded by sherrysdesigns.

Here is an example of contrast. The covered bridge in the background againstthe green trees creates a contrast. Contrast in photographic composition is an effective means of directing the viewer's attention to the center of interest. Positioning of subject elements to create contrast gives them added emphasis and directs the viewer's attention.
When we speak of contrast as it relates to composition, we are referring to both tonal contrast, as in black-and-white photography, and color contrast as it relates to color photography. In black-and-white photography, contrast is the difference in subject tones from white-to-gray-to-black or from the lightest tone to the darkest tone. In color photography different colors create contrast.