In the same way that a gently curving path through a forest or field is more interesting to explore than a straight rigid one, a graceful curving line in a photograph is more interesting for the eye to explore. Rather than delivering the eye from one point to another with great efficiency (railroad tracks pointing to the horizon, for example), curved lines entice your eye to wander, to study details along the way at a more leisurely pace and, as Glen Cambell once sang (does anyone remember Glen Cambell?), they are simply more gentle on your mind (actually Glen sang "Gentle on My Mind" but I think we can invoke some poetic license here). Curves invoke feelings of softness, slowness, gracefulness and even safety--you're less likely to fall off a gently curving rock, for example, than a sheer straight cliff.
Nature is a particularly rich source of soft curving lines and you can find them in everything from the human form (some have more curving lines that others, granted) to streams meandering through a meadow to the curve of an ocean beach. Interestingly, curves tend to work best in a photograph when you show only a section of them--as I did with this snippet of a bleeding heart branch. By cropping in on the line a bit you can isolate the most interesting part of the curve and, as with the old show biz adage, you leave the eye wanting more. Rather than photographing the entire curving limb of a saguaro cactus, for example, you might just close in on the elbow and reveal the interesting contrast between the rough texture of the plant and the softness of its shape.
Beautiful San Francisco
10 hours ago