It was W. Eugene Smith who asked, “What use is having a great depth of field if there is not an adequate depth of feeling?” In a sense, Smith was right. Without emotion, a photograph is a stale thing. However, depth of field is one of the photographer’s most important tools for creating emotion. By understanding how to adjust the aperture, I can isolate my subject or capture the entire scene with rich detail. The question becomes, “How do I use the aperture to achieve the greatest emotional effect?”
In many instances, a wide aperture is better. If you’ve ever seen Smith’s photo “Nun Waiting for Survivors,” you’ll know exactly what I mean. He elected to use a wide aperture to create a narrow depth of field, keeping only the nun herself in focus. The background – and to some extent, the foreground – is blurred just enough so that the nun takes center stage in the image. However, you can see enough of the background to understand that this image was taken in a bustling area, on perhaps a momentous occasion – feelings that are underscored by the nun’s expression and posture.
So how did Smith do it? For him, it would have been no small feat. While W. Eugene Smith sometimes used SLRs, he typically preferred rangefinder cameras. With a rangefinder, you cannot see the depth of field through the viewfinder. Most modern-day photographers can adjust the depth of field as they compose their images, but Smith relied on instinct and intimate knowledge of his equipment to create images like this.
With a modern digital SLR, you can recreate this narrow depth of field – often referred to as bokeh – quite easily by widening the aperture on your cameras lens. Smaller numbers (or f-stops) are wider aperture openings; when you turn the aperture ring to f/1.4, the aperture will be much bigger than if you set it to f/22.
As you open up the aperture, you’ll always need to be mindful of one thing: Wider apertures let in more light. That means you’ll need to compensate by adjusting either the shutter speed or the ISO setting. On a bright, sunny day, an aperture set at f/1.0 may require an ISO of 100 with a shutter speed of 1/2000 or more to prevent overexposed images.
If you’d prefer an image that is sharp from the foreground to the background, you’ll need to “stop down” or narrow your aperture. When you narrow the aperture, you’ll need to lower your shutter speed and increase the ISO setting. However, you’ll need to remember that shutter speed and ISO settings will have their own effects on your image. Slow shutter speeds can create motion blur, while high ISO settings sometimes result in “noisy” photos.
At wide apertures, many lenses have a tendency to “go soft.” This means that everything in the photo – even the parts that seem focused – are faintly blurred. In some applications, such as wedding portraits, this “soft focus” look can be beautiful. At other times, your images will call for as much clarity as possible. Each lens is different, so you will need to experiment to figure out the point at which your lenses start to go soft.
Ansel Adams was famous for using incredibly small apertures to achieve a deep depth of field. He went so far as to found a group in 1934 called Group f/64. Adams and the rest of Group f/64 believed that photography should be less about artistic soft focus effects and more about the sharp, clear pictures that can only be produced by using tiny apertures.
Group f/64 typically used large format cameras because these were some of the only cameras available that had lenses capable of tiny apertures. Their style also meant that all photos – even those taken in broad daylight – had to be long exposures.
Fortunately for us, there is no need for the modern-day photographers to resort to such extreme measures to achieve perfect clarity. The vast majority of lenses you will find top out at f/22, and they have excellent optics capable of creating crystal clear images. For the most part, if you keep your aperture settings toward the middle or the narrow end of the range, your images will have the sharpness and detail that Adams prized.
Are wide apertures preferable to narrow ones? As Adams once said, “There are no rules for good photographs; there are only good photographs.” I’ve used apertures both large and small in my work. Your choice needs to be based on your style, your environment and, most of all, the emotion you’re trying to convey.