If you are just starting out with photography, you’re learning about plenty of new concepts. Depth of field is one of them. Although it’s one of the essential elements to understand, it can be overwhelming if you’re completely new to it. Therefore, I have come up with the ultimate beginner’s guide to controlling depth of field with lens aperture. While I focus on nature photography, you’ll find this guide handy regardless of the genre you generally shoot. So, let’s get right into it!
What is the depth of field in photography?
Depth of field aka DOF is the area in the photograph which is sharp and focused. This area is parallel to the plane of the camera image sensor.
What is bokeh in photography?
Bokeh is the quality of the blur produced for the area which is out of focus in the image. This area is generally referred to as the background of the picture. Smooth blur produced in the background is called a bokeh effect. (Blur can be in the foreground as well )
Primarily following are the four factors which affect background blur or bokeh
- Lens aperture setting
- The focal length of the lens
- Distance between the object and background
- Distance between the camera and object
The lens aperture affects the quality of the background blur in the most significant manner.
First, we will start learning how to use the lens aperture setting to control the background blur and achieve the beautiful bokeh effect.
How to achieve bokeh effect using the lens aperture
Let’s understand what are the different types of depth of field ( DOF ). There are essentially two types:
Shallow depth of field: the depth of field with a shorter area of the image in focus. The shallow depth of field is critical in wildlife portraits, birds and flower images, etc.
Deep depth of field: the depth of field with a more extended area of the image in focus. The deep depth of field is desirable in landscape images, wildlife habitat images, bird flocks, and wide-angle nature images.
Top fundamental tips on controlling depth of field using lens aperture
The lens aperture is your best friend as it is the most critical factor which controls the depth of field in your photograph. You will achieve precise control over background blur or bokeh by changing the lens aperture.
To better understand this fundamental concept, I have created a simple illustration for you. Let’s dive right into it: we will photograph a mighty elephant with a beautiful green forest in the background. Our target is to capture a sharp image of an elephant with a smooth blur green background. Hence object is an elephant with the forest as a background.
The lens is positioned at a constant distance from an elephant. It’s zoomed in to its maximum focal length such as 400mm or 500mm (or a fixed telephoto lens is used). For all three illustrations, the focal length of the lens is kept constant. We will be only changing the lens aperture:
- The smaller the f-stop or aperture number, the bigger the lens opening (Example: f/4, f/5.6 )
- The larger the f-stop or aperture number, the smaller the lens opening ( Example: f/11, f/16 )
- In the first illustration, we will set the lens aperture to f/5.6. The lens is wide open to an aperture value of f/5.6. With smaller aperture number such as f/5.6, the lens will be wide open. We will achieve a shallow depth of field with the lens wide open. This results in the smooth blurry background and beautiful bokeh effect. Hence we will capture sharply focused elephant with beautiful blur background of the forest.
- Let’s refer the second illustration where the aperture is stopped down to f/8. As the aperture number starts increasing the lens opening starts decreasing. With f/8 aperture, deep depth of field is achieved. With a deep depth of field, the quality of the background blur is less as compared to that of f/5.6 aperture. Aperture f/8 will give us a decent bokeh effect.
- Finally, for the third illustration where the lens is stopped down to f/16, lens opening is smaller as compared to f/5.6 and f/8. With f/16 aperture depth of field will be deeper. The elephant in the foreground will be in focus along with some part of the background forest. Quality of the background blur or bokeh will be poor when the lens is stopped down to f/16.
Shallow depth of field and deep depth of field both are essential for wildlife and nature photography. Each one is having its own unique set of advantages and application areas. For example, you will be using a shallow depth of field for an animal portrait whereas the deep depth of field will be applied in landscape images.
How I did it in the field
Damn… Enough of theory! Even I am feeling dizzy while creating the illustrations on my MacBook. Let’s get boots on the ground and take a nature walk around the lake in the winter morning. Here I will show you step by step procedure on how I control the depth of field and achieve bokeh.
Kingfisher perched around the lake with trees in the background is my object today.
Photo gear: I am using a Nikon D7100 camera and Nikon 200mm – 500mm f/5.6 lens. The lens is mounted on the Gitzo tripod for steady support. By the way, start using a tripod for your bird images and see the quality of your images getting awesome!
I have set up Nikon D7100 in Manual mode. I am using manual mode because I want to control both shutter speed and aperture as well. Nikon 200mm-500mm f/5.6 lens is zoomed to the telephoto end which is 500mm. Kingfisher is auto-focused.
To illustrate the effect of the aperture change on the depth of field and bokeh – I keep the focal length and the shutter speed constant for all three images as below.
- In the first image, the aperture is stopped down to f/16. As we have seen earlier, a higher number of the aperture means a smaller lens opening. Higher aperture number is used to increase the depth of field. Deep depth of field is achieved using f/16 aperture. Hence as you can see in the image, the kingfisher is focused and since the depth of field is more the quality of the bokeh is poor. The background blur is not as creamy and smooth as intended.
- In the second image, the aperture is opened up to f/8. With aperture f/8, the depth of field is reduced as compared to f/16 aperture. Quality of the background blur is better than that of f/16 aperture.
- In the third image, the aperture is wide open to f/5.6. Smaller the aperture number larger the lens opening. Aperture f/5.6 is having a shallow depth of field. Shallow depth of field is producing beautiful background blur, and smooth bokeh effect is achieved. Sharply focused kingfisher against smooth bokeh pops up nicely.
As you can see, significant image quality improvement for the kingfisher image captured from f/16, f/8 to f/5.6 aperture. Image quality improvement is achieved mainly because of the quality of the bokeh or background blur. Since other settings such as an object, focal length, shutter speed, and object distance are kept identical.
I am glad you are with me so far! Here is good news for you – We have just completed theory and in-class practical session.
Now it’s time for you to get ready for exciting hands-on creation. To achieve the best bokeh results for you, I have made a simple step by step procedure, which will help you to achieve beautiful bokeh effect using lens aperture.
Bonus tip: Step-by-step procedure to achieve beautiful and smooth bokeh effect for your images
- Object – choose a simple object such as a flower in the garden with no clutter in the background for at least distance of 10ft ( Choose decent morning sunlight- between 8 am to 10 am)
- Camera and lens setup – set your camera and lens on the tripod for steady support at the usual distance from the flower
- Keep the lens focal length to a constant value such as 100mm or 200mm in such a way that object flower will approximately cover ⅓ rd area of the image
- Set the camera to manual mode with shutter speed constant. Set ISO value to 400. Choose the shutter speed based on light condition and the wind blowing. Usually shutter speeds such as 1/200s, 1/320 s or 1/400s are good enough.
- Note- If you don’t want to use manual mode, then choose Aperture priority mode with ISO set up to 400. In the aperture, the priority mode camera will automatically adjust the shutter speed based on the aperture value you choose.
- Focus on the flower. Auto-focus or manual focus both are perfectly ok as long as the flower is precisely focused.
- Increase the value of the f-stop to f/16 (or stop down the lens to f/16 ). Press the shutter release button and capture the image. Open the lens aperture to f/11 and click the image. Repeat this step of aperture value of f/8, f/5.6 and f/4 (if available for your lens).
- Copy the images captured with an aperture value of f/16, f/11, f/8, and f/5.6 on the computer and observe them on the computer screen. You will start noticing the depth of field reduced from aperture f/16 to f/5.6. Quality of the background blur or bokeh increase and starts becoming smooth and beautiful when you open up the lens aperture from f/16 towards f/5.6
Congratulations! You have just learned how to control depth of field and achieve beautiful bokeh effect for your nature and wildlife images using lens aperture.
Practice this technique on the simple object in nature, such as a flower. Gradually start using this simple technique on your wildlife and nature images. With regular practice of controlling lens aperture, you will start achieving beautiful bokeh effect for your wildlife and nature images.
Please feel free to share your thoughts and ideas in the comment below. If you find this article useful, Don’t forget to share on it with your friends.
About the Author
Shreyas S. Yadav is an engineer, wildlife and nature photographer from India. He is also a writer and lifelong adventure explorer. Through his writings, he teaches about digital post-processing and nature photography. He shares field techniques about nature photography, post-processing and wildlife photo stories on his website.