Edward Weston once said, "Consulting the rules of composition before taking a photograph is like consulting the laws of gravity before going for a walk."
Point well taken.
Composition, good composition, is one of those things that, for serious photographers, should become instinctive and automatic: You know, like one foot in front of another without, prior to walking, feeling the need to brush up on Isaac Newton's Law of Universal Gravitation.
Although we don't need to learn the laws of gravity in order to walk, it's a pretty good idea to know something of the rules of composition -- what works and what doesn't work -- in order to, at some point, become photographers who naturally, instinctively, and automatically apply the rules of composition (or break those rules) in effective ways.
In both my ebooks, Guerrilla Glamour and Guerrilla Headshots, I wrote a fair amount about composition. While going on about the various elements of composition, I placed special emphasis on diagonal lines. Not simply because I tend to incorporate diagonal lines in my images whenever I can, but because diagonal lines are, in a word, powerful. Make that, visually powerful.
The power of diagonal lines can be obvious or subtle. Regardless, they add much value to almost any photograph-- whether they're applied to genres as diverse as architectural photography and glamour photography or even, when they can be, employed when snapping headshots.
In glamour photography, backgrounds, shooting environments, wardrobe and accessories aside, diagonal lines can be produced by pose. People have arms and legs. Those arms and legs, in their most basic state, represent lines. The lines represented by arms and legs can be directed to create diagonal lines within the vertical and horizontal rectangular dimensions of your viewfinder. Those diagonal lines help lead the viewer's eyes to where you want them to go. In fact, they nearly force the viewer's eyes in certain directions. That's why diagonal lines are such powerful constructs to apply to your photos.
Getting back to Edward Weston's quote, calling on the rules of composition (diagonal lines included) doesn't need to be something that is consciously considered. In fact, the more instinctive and second nature it becomes, the more it seems a natural element of the image rather than something that is forced or obviously intentional. (That's not to say forcing compositional elements or having them appear intentional can't be done to great effect.)
How do employing compositional techniques like diagonal lines become automatic? Well, the same way, as babies, we learn to walk. At first, our minds and bodies are carefully, purposefully, and cautiously taking steps. Soon, those steps become more fluid and natural. Finally, walking becomes near thoughtless and automatic. The same chronology applies to employing effective composition. After some time of consciously and purposefully framing your pictures with nods to various compositional techniques, you will eventually begin automatically framing your images and directing your models in ways that reflect those "rules" of composition without even thinking about them.
The pretty girl at the top is another of Faye. (I used a Faye pic in my previous update, "Focus.") This image of Faye, unlike the previous, is a one-light shot using a 300WS monolight in front, modified with a shoot-thru umbrella. Faye has posed her body in a standard, "S-Curve," glamour pose. There are a number of diagonal lines represented in the image. They all work to add visual value to the photo. The diagonals formed by her arms lead the viewers' eyes to her very pretty, freckled face.