The Principle of Design I was assigned was contrast. Contrast is the placement of objects or things in a picture to show opposite elements(light and dark, smooth and rough, etc.), and to create a visual interest or area of interest.
I took this photo of Jenna going down the stairs while I was at the top. I put the photo in black and white and adjusted the shadows. This photo shows contrast because her blonde hair stands out creating this point of interest against the dark background of the floor and wall.