If you wish to compose a grand landscape with everything in focus, from the immediate foreground to the infinite horizon, there is but one aperture that can do that for you. If, on the other hand, what you’re after is a portrait against a blurry background so that only your subject is sharp, there are only two apertures capable of rendering that background to the blur that you need. And if you’re looking to isolate a butterfly sipping nectar from a purple coneflower, are you confident that your aperture choice will render the butterfly in exacting sharpness from front to back?
As we are about to discover on the following pages, the right aperture (and/or shutter speed) does play a powerful role in dictating the visual weight and overall balance of a given composition. Because aperture controls what is commonly referred to as depth of field (a.k.a. sharpness), it defines which part of the image has the “visual weight,” or emphasis—a serious tool of photographic composition. Once you embrace aperture as a sharpening tool, able to “sculpt” the point of emphasis, you will quickly realize that the right aperture is behind any successful composition. Although covered in more detail in later chapters, the right lens choice and the distance the subject is from its surroundings also play roles in an image’s overall sharpness, but again, it is first and foremost the right aperture that leads the way toward effective visual weight. And when the visual weight is executed to perfection, a major component of compositional excellence has been achieved.
If there’s one bit of advice that bears constant repeating, it is this: Pay close attention to your aperture choice, because many times, the wrong aperture choice ruins an otherwise wonderful composition!
Take a look at the top image of the tulip. It’s a wonderful image of a lone tulip against a background of out-of-focus tones, shapes, and colors. This is what each and every one of us would see if we all stood in this spot and shot with our 70–200mm zoom lens using a 200mm focal length and with the aid of a small extension tube. But just because this is what we all would see as we looked through the viewfinder is no guarantee that this is what we will record on our image sensors. If, in your excitement over framing a shot like this, you fail to notice that you are, in fact, at an aperture of f/16, you will record the tulip with a much busier background. As the bottom image of the tulip clearly shows, we no longer have a background of out-of-focus tones, shapes, and colors but rather a defined background of other tulips, creating a much busier background.
Top: Nikon D300S with 70–200mm lens, f/5.6 for 1/1000 sec., ISO 200; Bottom: Nikon D300S with 70–200mm lens, f/16 for 1/125 sec., ISO 200