Depth of Field, Part I
Becoming a great photographer takes a lot of dedication, proper equipment, and skill. Many people wouldn’t even try without the first two, and equipment (once you know what to buy) is mostly a matter of money. The highest hurdle, therefore, is likely skill—acquiring the range of skills needed to understand the more technical aspects of photography such as when and how to use depth of field, manual exposure, aperture preferred, evaluative/matrix metering, spot metering, and exposure compensation, among others. Unless luck is strongly on your side, consistently capturing good images without such technical expertise is rare—even with the “smart” cameras on the market today. And while I love the versatility of many of these new features, I’ll also say that they often make us lazy and feel more competent than we actually are.
In 1973 I had an awakening. I was studying with Ansel Adams in Yosemite National Park and was, by most measures, an OK photographer and a fair black and white printer. That period of intense study revolutionized the way I saw and worked with photography. Ansel taught and demonstrated that how we visualize images before shooting and the more comprehensive our technical knowledge, the stronger our photographs. Day after day, we practiced really slowing down and taking the time to see and plan our images before shooting—an exercise in patience and restraint which is increasingly difficult with digital cameras. We also learned the technique of Zone system exposure, which Ansel invented and that I teach and use today. Neither was easy to learn, but both have endured and ground my process today. I was reminded of the power of this learning curve just last week while teaching a Basic Photography workshop here in Missoula. Many of the students already had a fair knowledge and shooting base, but with intense practice and an emphasis on technical skills and planning ahead, their proficiency skyrocketed in just seven days.
In this article, I will discuss depth of field, one of the essential technical skills of photography. Before I do, I want to remind you of the full f stops: f 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, and 45—with f 1 being a very large opening and f 45 a very small opening. No lens made will have this entire range. There are also partial f stops such as f 1.8 and f 3.5.
Depth of field is one of the hardest topics to master. True, with proper knowledge a new photographer can understand the concept; yet really knowing it requires studying example after example with regard to shooting techniques. A simple definition of depth of field is the area of a photograph in front and behind the focus point that appears perfectly sharp. There are three elements that are generally considered to control depth of field: aperture, lens length and focus distance.
Aperture (f stop). The smaller the aperture, the greater the depth of field. For example, f 16, 22, and 32 give a photographer more depth of field; conversely f 2, 2.8, and 4 yield a shallower depth of field. A medium depth of field is achieved with f 5.6, 8, and 11.
NOTE: When I say a small aperture such as f 22, what I mean is a small opening in the lens despite the fact that the actual number 22 is larger. When I talk about large or small f stops, I am always referring to the size of the opening in the lens, not the number.
Length of the Lens. The shorter the lens (10 mm, 16 mm, 24 mm), the greater the depth of field. The longer the lens, the less depth of field. This is why when a wide-angle lens is fully open (with a larger aperture like f 2.8), we still have a tremendous depth of field and cannot make the background that soft. With a long lens (300 mm), we have a fairly shallow depth of field even when we use the smallest aperture (f 22 or 32).
Focus Distance. The closer we focus in a given scene, the less inherent depth of field we have. If the point of focus is farther away, we have more depth of field. This is why lenses made for close-up photography often stop down to f 32 or 45 to yield as much depth of field as possible. When extremely close to a subject, as in macro, depth of field is incredibly shallow and one or two additional stops make all the difference.
Capturing creative shots requires understanding depth of field. While I hesitate to generalize, I am going to do so below as I discuss the technique’s role in various fields. As such, please keep in mind there are exceptions to what I say.
- Landscape Photography. For landscapes we usually want a great depth of field and therefore assume a small f stop such as 16 or 22 is best. And this is usually the case—unless, that is, the scene is far away and contains no foreground. In this instance, we don’t need as much depth of field and can use a middle f stop such f 8 or 11. To this end, most advanced amateurs use a tripod when shooting landscapes because they know a small f stop allows so little light through the lens that the shutter speed is often slow, usually too slow to hand-hold the camera. Raising the ISO can give a faster shutter speed, but quality can be compromised.
- Architectural Photography. Usually we want everything sharp, so again we’re using small f stops; likewise, this means a slower shutter speed and a tripod.
- Macro/Micro Photography. When shooting close-up images, I usually think of depth of field as being used in two ways. Let’s say I’m shooting flowers….
- I want as much depth of field as possible (though it is still pretty shallow because I am so close), so I use f stops 22, 32, or 45 to maximize the little depth of field I already have. These shutter speeds usually require a tripod to make the images sharp because my aperture is so small.
- I may want only one portion of the flower sharp, which means a small depth of field is actually possible. On most macro lenses, this would be f 2.8. In this case, I’d likely have a shutter speed fast enough to hand-hold my camera since my f stop is allowing in so much light. Still, the tripod helps ensure strong composition, so I’d still use it.
NOTE: Since the above three areas of photography are commonly shot while traveling, investing in a small lightweight tripod is a good idea.
- Portraits. Portraits usually require a shallow depth of field to maintain a soft and less-focused background. This is where a faster lens (f 2, 2.8) is useful due to the shallow depth of field those apertures give. Many times the kit lens that comes with a camera is f 5.6 at its widest, and therefore incapable of giving a shallow depth of field. For head and shoulder portraits, a lens around 80-135 mm is often best for a natural look. In portraits with a shallow depth of field, the wide aperture usually allows one to hand-hold the lens because of the faster shutter speed.
- Wildlife and Birds. This type of photography is shot with lenses usually 300 mm or longer. Lenses this long already have a shallow depth of field; to keep it even more shallow, one would usually shoot at the widest aperture, either f 2.8 or 4. Again, the shallow depth of field quickens the shutter speed so sharper images are possible while hand-holding—especially if optical stabilization is built in. Still, using a tripod is best.
I hope the examples above have made depth of field a little more accessible. For examples of depth of field take a look at my slideshow of examples. Again, it really isn’t the concepts that are challenging, but rather the mastering of them. And because depth of field is such a complex topic, my next article will continue from where I left off.
Before I end I want to take a moment to thank my most recent group of students. The twelve of you reminded me that not only are the basics essential, but they aren’t as easy to learn as a seasoned photographer may remember. Both learning and teaching photography are humbling endeavors. Thank you Elizabeth, Erika, Nikki, Genevieve, Tim, Glenda, Roberta, Scott, Jennifer, Amy, Beth, and Alex.