The Four Basic Principles of this ad

When analyzing this ad for the four basic principles of design I had to think about a few things.
There isn't a lot of contrast in the picture, as far as text or size.  There is however a color contrast between the brightly colored clothing of the workers and the dark background of the picture.  Repetition in the picture comes from the same use of text and from the same use of color.  The color in the uniforms are repeated on each person from their shirt and pants, all the way down to their hat and gloves. The alignment of the picture is slightly to the right, but the purpose for that is to show the big mountain of trash in the background.  The photographer would have missed the "shot" if they would have centered the men in the photo.  The proximity in this picture is that the men are grouped very close together, along with the mountain of trash, and the tagline for the ad.