The Art of Composition part 3

In the last article of this Art of Composition series, I discussed how depth of field is really a function of distance - distance from the subject to the background, and more importantly, distance from the lens to the subject. But like everything in photography, there is more than meets the eye here.

It’s important to understand that when we talk about depth of field, that number, that range such as 5.5 or 8.5 feet is what appears to be acceptably in focus. Emphasis must be placed on this for a reason here. Technically speaking, much like how our own eyes work, there is only one single point in a photograph that is in focus. Depth of field is all about the illusion of what else “seems like” it’s also in focus. And outside of our so-called depth of field bubble, things do not suddenly just become soft and creamy. Or, what I like to call, bokehlicious.

Just because areas of the photograph are going to be out of focus, this does not mean they will be out of details. You will easily make out individual sticks and twigs and leaves and all the other chaos of nature that can distract and even destroy a composition. But just how much detail depends on how large or small your depth of field is to begin with.

Think of it in terms of autofocus for a moment. We all know what it looks like when our focus didn’t quite lock on, or it didn’t quite go that extra step to obtain “critical focus.” When our focus is slightly off, be it only an inch or even a foot or two, we still see all the details in the bird or mammal. We can still tell exactly what it is we were photographing. And sometimes we may keep the image even though the subject was slightly out of focus.

It’s the same thing when it comes to depth of field, and it really does all boil back down to the fact that there is but only one small spot in your photograph that is actually in focus – regardless of whether you use f/2.8 or f/22 and regardless of how close or far away you are. The depth of field we see is just a matter of how quickly the illusion of focus falls off from that one spot, with everything becoming more and more “out of focus,” the further it gets from that point. The larger the depth of field to begin with, the more gradual this fall off is. Likewise, the smaller, or shallower, the depth of field, the quicker and more immediate the fall of is.

Another important component to the equation here is focal length. Quite simply, the longer the lens, the shallower the depth of field – similar to how the closer you are to your subject, the shallower the depth of field as well.

Let’s take a look at some more DOF calculations like we did with the last article. And in this instance, let’s say we are photographing a subject that is 50 meters away.

Yes, I realize that this is a long way out. But I would wager that if you started carrying a range finder around with you in the field, you would likely find that you routinely photograph animals from this distance. Whether you should be doing that is a different matter entirely, of course. But the fact remains it’s very common.

At 50 meters, when using a full frame camera with a 600mm lens at f/4, we have a DOF of 1.65 meters – essentially 5.5 feet.

With a 400mm at f/2.8, however, this becomes 2.6 meters – which is over 8.5 feet.

Even though the 400mm has a larger aperture, and we all “know” that f/2.8 is supposed to have a much shallower depth of field than f/4, the DOF in this example is larger due to the focal length.

Now, if I am on the high plains of Montana photographing pronghorn with distant backgrounds, an extra 3 feet of DOF means nothing to me. But in the boreal forest photographing black bears, or in the rainforest photographing sloths and monkeys and birds, an extra 3 feet can make a very big difference in the composition of the photograph.

For me, this is exactly why I carry both a 400mm and either a 600 or an 800 with me. However, I also realize this isn’t feasible for most people.

While lens length has a significant impact upon the depth of field in your photograph, from the perspective of being in the field, it might be easier to think of both distance and focal length as a matter of how large the subject is on the image sensor. With a 600, you can work from greater distances than you can with a 400mm all the while creating the same if not better depth of field, despite having a smaller maximum aperture.

If you can’t get closer, work with a longer lens. If you don’t have a longer lens then become a better naturalist and learn how to get closer. But whatever you do, don’t rely on cropping the photograph on the computer if you care at all about being able to control the depth of field and amount of detail in an image that is competing with your subject (more on this later).

Examples may be in order.

This first photograph of a coatimundi from Panama and was created with a 70-200mm lens at f/2.8. I used this lens to capture more of the environment. More environment equals more story telling potential, and as a working wildlife photographer, I can assure you this also equates to more sales. However, even though I was photographing at f/2.8, and even though the background in this photograph was probably 30 or more meters behind my subject, due to the shorter focal length of the lens, there is a significant amount of detail left in that background. So much detail, in fact, that it all begins to flirt with overpowering the subject in the photograph.

Given the amount of detail and definition in the background, you can easily see exactly where each tree is. Because the amount of bokeh with this lens and at this distance is far less than the other photos included here, you find that the edges of those trees become very distinct lines that can very easily destroy a photograph. Lines are something we will discuss once we begin talking about the elements of design later on. But in the meantime, take a look at the head of my coatimundi and notice how that the slope of the forehead to nose comes close to lining up perfectly with the edge and angle of the tree behind him. If this tree had been just a few feet closer to the animal, which would have rendered more detail and definition, this photograph would have likely ended up in the trash bin.

This is exactly why I wanted to begin my series on the art of composition with a discussion of depth of field.

Much like the coatimundi photograph above, this next example is of medium sized mammals in the forest. In this instance, I was photographing with a prime 400mm f/2.8 lens set “wide open.” Wide open, of course, meaning that I was photographing at the widest / largest aperture, which is f/2.8.

The first thing you need to understand about this photograph is that the background was roughly the same distance as the one in the photograph with the coati. At 30 meters away, with a 400mm f/2.8 lens, there is virtually zero detail in the background save for the one tree growing diagonally about 2 feet behind the subjects. Zero detail means zero things I need to worry about potentially distracting from my bear cubs back there. And all of this allows me to simplify the composition down to as few parts as possible.

For both these photographs, I was working in a forest. That means no matter what, there will always be various things I need to juggle in order to sus out a solid composition. However, because I was working with a 400mm at f/2.8, the image magnification created a shallower depth of field than the 70-200 lens in the other photograph. And this, along with my distance to the cubs, allowed me to solve the problem of a distracting background entirely, even though it was the same distance as in the coati photograph. Had I been another 25 meters away with the idea in mind that I could just crop in later, you would see significantly more detail in that background.

Remember, all of this is at f/2.8. How different would these two backgrounds have been if I were photographing with f/5.6 or f/6.3? How different would they have been if I had been further back assuming I could just “crop” the photograph in Lightroom or Photoshop?

Now for something completely different.

With this photo of a burrowing owl, I used a 600mm f/4 lens set wide open.

Here, our little burrowing owl is completely surrounded by grass. Grass in the foreground. Grass in the background. All that grass comes with sharp edges. All that grass has the tendency to reflect light. And for me, the reflective light and edges of the grass created distinct and distracting lines that needed to be “dealt with” in the composition – not unlike what I mentioned above with the coati photograph.

However, by using a 600mm lens at f/4, and moving in very close, the shallower depth of field associated with the increased image magnification allowed me to completely remove any and all details from everything around my owl. It’s not that the grass simply falls outside of the DOF bubble here. There is so much bokeh here that the grass itself is not even recognizable – even though it’s mere inches away from the owl.

My 600mm f/4 lens has a minimum focusing distance of 14.4 feet. This owl was right at the edge of my minimum focusing distance. So, when we run the calculations on this at, say, 15 feet, with a 600mm lens, set to f/4, we find a DOF of around half an inch. And it’s this extremely shallow depth of field that allowed me to create so much bokeh as to turn what would have otherwise been distracting lines in the grass into a soft and ephemeral foreground and background (I can't wait to start talking about the importance of lines).

As you can see, DOF is much more complex than just apertures. And hopefully by now you can see why I believe begining with a discussion on depth of field is an important starting point for a discussion on composition. We cannot always choose what we want to have inside of our compositions. But by understanding depth of field, we can often choose how much detail we wish to show of those other "things."