Curves create a gentle, meandering path that leads the viewer through your image to the subject (Figure 4.1). Curves are lines but with a softer feel to them. With an S-curve, the path to your subject is not as direct as a line, so it gives a sense of peace and calm. S-curves are great leading lines to a subject (Figure 4.2), and they are such strong elements that they can stand alone as the subject itself (Figure 4.3). Whenever I see an S-curve, my eye follows it to see where it leads and to see whether it will make a good photograph.
Figure 4.1 Centering myself in the middle of the path and using a fairly small aperture (Chapter 2) for increased depth of field creates a composition that invites the viewer to step into the frame and wander down the path and through the forest. I find S-curves to be friendly lead-in lines in composition.
Figure 4.2 The curve of a great blue heron's neck leads from the left side of the frame to the fish he has clamped in his beak, creating a very natural pose.
Figure 4.3 An S-curve is such a strong element in composition that the curve itself can be the subject, as in this image of a curved staircase at Fort Point in San Francisco. Using a Fisheye lens emphasized the curvature of the staircase. Hand-holding the camera at 1/7 sec. required a faster ISO to gain enough depth and sharpness.