The Tuesday Composition: Edges

Much like our eyes are attracted to highlights in an image, our eyes and brains are not only attracted to edges in an image but they also help us in seeing them, allowing us to perceive those edges even when they’re weak or incomplete. This makes edges (lines, contours) an important element of composition.

(That we respond to edges, even minimal ones, is not simply a cultural artifact: The detection and exaggeration of edges in scenes is a function of the brain, in particular, it is one of many functions of the primary visual cortex. This part of the brain operates much in the same way that software sharpening does, if you look near a defined edge between a light and dark area in an image, the lighter area appears even lighter right next to the boundary, the dark edge appears even darker on the other side of the boundary.)

“Snowy Pinnacles” provides a simple example of these principles. As we discussed last week, many viewers of this image will first have their attention drawn to the moon because of our “attraction to highlights”, but from there, it’s likely that many viewers will then begin to look down and to the right, along the edge of the taller pinnacle until they reach the lower pinnacle at the lower right.

The importance of edges is also easily seen in the Backlit Foliage image. The two primary fork-shaped branches quickly capture our attention, and the eye tends to wander back and forth between the foliage in the top left and the foliage in the bottom right of this image. It is only after a few traverses of this diagonal that many viewers start wondering what the white color in the background is. (It’s part of a waterfall.)

Some of you will have noticed that the thin branches are really composed of two edges, not one. While that’s analytically true, to the eye those very thin branches act together, more like a single stronger edge rather than two separate ones, and as a result I (and many other writers) will describe features like those branches “as if” they were single edges. Please forgive the apparent imprecision.

Of course, most images aren’t quite so easy to analyze, and the way a given person will look at an image is far less predictable than one might gather from this description. But these principles do have value. When we notice important edges or lines in a photograph, we can look to be sure that the parts of the image near the line, as well as the parts of the image at the ends of the line have good interest. We can think about composing the image so that the lines are diagonal if we want a more dynamic image, or vertical or horizontal if we want a more static or formal look (more on this in a future installment). We can look at ways of strengthening the effect of a line by increasing the contrast across that line, or by composing an image so that an important edge isn’t occluded by some other object. In all these ways and more, understanding the importance of edges can be an essential part of making more effective photographs.

Thank you for all the great response to last week’s installment on highlights! As a reminder, I’m still interested in seeing examples of your images for some compositional feedback. If that idea appeals to you, drop me an email at joedecker (at) gmail (dot) com. Thanks!