How to Select Correct Depth of Field in Nature Photography
Depth of field (DOF) is defined as the area in your frame where the photo is acceptably sharp. Getting the right amount of sharpness in nature photography can be quite challenging. Most photographers know that aperture impacts DOF, but there are many other interrelated factors that also affect it. Because each of these factors work closely together, it is not always easy to predict their impact.
To add yet another dimension to this challenge, DOF is often an artistic choice. This fact can often be particularly challenging to beginner nature photographers.
It’s no wonder that one of the questions we hear most frequently is… how do I get my depth of field correct?
Let’s start with the basics. As I already mentioned, aperture impacts a frame’s DOF. So, we will start there. The technical explanation for adjusting aperture settings is fairly simple: the wider the aperture, the narrower your depth of field becomes. Although it looks simple on paper, many students have a difficult time visualizing the concept of depth of field in practice.
I’ll give you a practical example of DOF out in the field. During one of my trips to Oregon, I shot two photographs in a lovely, open field. One flower in particular called attention to its tiny self with a remarkable burst of color. For the first shot below, I used an aperture of 3.5 (f/3.5). Notice how soft the background appears. Only the flower itself and a few blades of grass are in focus.
Now look at the second photo (above). I took this shot at f/16. With a much narrower aperture, the result is obvious. The depth of field is much wider. In this image, you can far more leaves and grass in the background as well as a bit of brown. For me, all of these details are distractions that draw your eyes away from my tiny subject – the flower.
You may also notice that I’ve lost some of the sharp details of the flower itself. This is part of the trade-off when you are working with a narrow depth of field. I love the effect – but you may wish to choose an aperture between f/3.5 and f/16 to get a little more sharpness on your flower and a little less softness in your background. This is an artistic choice that every nature photographer must make.
In this case, I prefer a wider aperture and the resulting narrow depth of field. The soft background leaves the image feeling soft and dreamy. It also serves to eliminate a lot of distracting elements.
Of course, the discussion of aperture and depth of field is far broader than this, but these two photographs make a great jumping-off point for a detailed discussion of the basic concepts.
What Variables Impact Depth of Field
Before you can select a correct depth of field, you must master how to manipulate depth of field. Effectively manipulating DOF depends upon four variables: aperture, focus distance, focal length, and sensor size.
Aperture is the opening in your camera lens which determines how much light the camera lets in. With everything else being equal, a wide aperture creates shallow depth of field, and a narrow aperture creates a wide depth of field. Some cameras allow you to preview depth of field on the LCD. Others have a depth of field preview button which allows you to see the actual depth of field on the screen.
If your focus distance decreases, your depth of field also decreases if everything else remains the same. One good way to increase your depth of field is to move away from your subject. The subject gets smaller in the frame and has a bigger depth of field. There is a trade-off between the size of your subject and depth of field.
If you use two different lenses with the same focal point and aperture, the longer lens displays a shallower depth of field. Of course, the composition also displays differently with the narrower field of view on the longer lens.
Smaller sensors have a wider DOF if you keep the field of view the same. This is a tricky concept to understand. Sensor size changes your field of view for any given focal length and aperture. Because of this, shooting the same scene with a smaller sensor requires you to step away from the subject to keep the field of view the same. This translates into a larger DOF.
Of the four variables listed above, controlling aperture is the most practical method for changing your depth of field in nature photography. Although there are occasions when you will move closer or further away from your subject and when you will change your focal length, but these depend on your location and the subject you are photographing. Sensor size is fixed by the camera you are using. All of this being considered, unless you are using two different camera bodies, aperture remains the most likely and practical method for changing your depth of field.
Let’s look at a real-life example of how I use these variables to get the correct depth of field.
Photographing Aspens with Shallow Depth of Field
I love aspens. Who doesn’t? But if you’ve tried to photograph trees, maybe you know that getting a shot you really like isn’t as easy as one may think. You pull out your camera in front of all that golden glory, and the resulting image just doesn’t do the scene justice.
So, how do you go about getting the shot you want in a nature or landscape photography situation?
What Do You Want to Capture?
The first step is to consider the most important element in your image. What are you trying to show? Is it the sweeping landscape? The beautiful mountainside? Or is the most important element of the image the colors themselves?
In my case with the aspen trees, I really wanted to show off the details on the trunks of the trees. But I also wanted to ensure that the colors were an important part of the photo. And, for anyone who has seen a lot of my photography, you may know that I am almost always looking for a minimalist nature photography composition. So, of course, that was part of my planning as well.
Finding the Right Nature Photography Composition
To satisfy my goal with the aspens, I needed a high vantage point with trees growing below me. Standing on the forest floor would put me too low – I’d end up with ground in the photo if I pointed my camera downward or even straight ahead. In addition, I’d end up with sky in the photo – as well as distortion – if I angled my wide angle lens upward. No good.
When we drove past this glen, I knew we were in the right place. The road was high enough as were the bases of the trees. And behind my scene was a vast mountain that blocked the brightness of the sky. Perfect.
The next step was to find the right tree for my “point of interest”. I walked up and down the road searching for the best one. But each time, there was something distracting behind the potential tree. A trunk that tilted at an odd angle – calling attention to itself. A broken branch. Too much white trunk behind and not enough golden color. Oftentimes, trees were simply too close to let just one stand out on its own.
This tree I settled on what just right – but only if I stood in the right place and used the correct focal length. There’s actually a dead trunk just behind this one, but I chose an angle that hides it. I then used a 200mm focal length to create a perfect composition that eliminated all distracting elements.
Select the Desired Depth of Field
When I finally found my photography composition, I took a few shots to decide how much depth of field I wanted. I chose an aperture (f/4) that would allow me to smooth the details in the background as much as possible – while keeping the tree in the foreground nice and sharp.
We were in this spot for about 20 minutes, and I have just one image to show for it. But it’s exactly the photo I wanted. As you can see, nature photography composition sometimes leaves aperture as the only element available to manipulate the depth of field in a photo.
And so, to summarize… select the nature photography composition that matches your artistic vision. Once you have selected the composition, determine which of the four variables you can use to best achieve the ideal depth of field to capture your desired image. Sometimes it may take a bit of experimentation and some time to find the correct combination. Be patient and remember that this is all part of the adventure. Make sure to have fun!