An incoming storm from the west lit by the early-morning frontlight was reason enough to stop my car and shoot this lone farmhouse. I used a critical aperture of f/8, pointed the camera down toward the green pasture, and adjusted my shutter speed until a -2/3 was indicated. I then recomposed and tilted the camera up toward the threatening sky before firing off several frames. “Who cares” what aperture you use when shooting landscapes such as this? After all, everything was at the same focal distance (infinity). But critical apertures matter.

“Who Cares?” Apertures

If it’s not a storytelling opportunity and it’s not a singular-theme/isolation opportunity, does it really matter what aperture you use? Yes and no. Let me explain. The world is filled with “Who cares?” compositions: “Who cares what aperture I use when shooting a portrait against a stone wall?” “Who cares what aperture I use when shooting autumn leaves on the forest floor?” Or, put another way, “Who cares what aperture I use when everything in my frame is at the same focused distance?”

In the storytelling and singular-theme/isolation sections, not one of the images was made with an aperture of f/8 or f/11. That’s certainly not because I don’t ever use these apertures; I use them a lot, actually, but only when depth of field is not a concern. Both f/8 and f/11 are what I refer to as middle-of-the-road apertures; they rarely tell a story (rendering all the visual information within a great depth in sharp focus), and they rarely isolate (rendering only a limited, selective amount of visual information in sharp focus).

Pretend for a moment that you find yourself walking along a beach. You come upon a lone seashell washed up on the smooth sand. You then raise your camera and 28–80mm lens to your eye, set the focal length to 50mm, look straight down, and then simply set the aperture to f/8 or f/11. In this instance, both the lone seashell and the sand are at the same focused distance, so you could photograph this scene at any aperture. This approach of “not caring” about what aperture you use applies to any composition where the subjects are at the same focal distance. However, rather than randomly choose an aperture, as some shooters do, I recommend that you use critical aperture. This is, simply, whichever aperture yields the optimum image sharpness and contrast. Apertures from f/8 to f/11 are often the sharpest and offer the greatest contrast in exposure.

To understand why apertures between f/8 and f/11 are so sharp, you need to know a little bit about lens construction and the way light enters a lens. Most lenses are constructed of elliptically shaped glass elements. Imagine for a moment that within the central area of these elliptical elements is a magnet—which is often called the “sweet spot”—designed to gather a specific amount of light and then funnel it through to the waiting film. The approximate diameter of this sweet spot is equivalent to the diameter f/8–f/11. So, for example, when the light enters a lens through a wide open aperture, such as f/2.8, the amount of light exceeds the area of the sweet spot and in turn scatters across the entire elliptical range and eventually onto the film. The effect is similar to pouring milk onto an upside-down bowl: only a little milk remains on the center while most of the milk spills off to the sides. Due to the scattering of the light, a wide open aperture doesn’t provide the kind of edge-to-edge sharpness that apertures of f/8 to f/11 can. When light passes through apertures of f/8 to f/11, it is confined to the sweet spot on the elliptical glass.

So who cares what aperture you use when shooting compositions where depth of field concerns are minimal at best? You should! And, ironically, you should use “Who cares?” apertures (f/8-f/11), if you want critical sharpness and great contrast.

Bryan Peterson has been a successful commercial photographer for more than thirty years. His first book, Understanding Exposure, was a runaway best-seller, with more than 250,000 copies sold. In addition to being a contributing editor at Popular Photography Magazine, he is also the author of Beyond Portraiture, Learning to See Creatively, and Understanding Digital Photography. His newest book, Understanding Shutter Speed, will be published this April. A well-known instructor, he is the founder of the online Perfect Picture School of Photography (www.ppsop.com). He lives in France. His book is available from Cord Camera, as well as other retailers.