Art of Photography: Exercise: Diagonals

Diagonals are ascending or descending lines so they add a dinamic look to the pictures because they draw a line to lead the eye through the frame. When diagonals intersect with other lines they suggest depth to the picture. They also give a sense of perspective which is emphasized with converging diagonals with a wide angle lens as shown in the third picture below (focal length: 18 mm).

As diagonals are lines they can help dividing the frame, or also framing a point in the picture. As we can see in the fist picture diagonals lead the attention to the small ship in order to the big one. If the three diagonal rope weren't there the small ship would be nearly imperceptible but the diagonals help us to look around the picture and we can notice the small boat more easily.

Here are some examples of diagonals. I've included another picture drawing these diagonals.