Depth of field is one of the key concepts in photography and a term you’ll hear a lot. After discussing exposure in great detail, I would like to turn to a different kind of control — depth of field (DOF). Ok, don’t jump, you are right: DOF is not a real control but more of a result of how you used the aperture control.
In simple words, depth of field is the term you use to describe what is inside the focused area of your image and what is left outside of it, turning into a blur. But why keep it simple when we can go in-depth and teach you all you need to know about the depth of field, right? Let’s go!
Introduction and basics
Understanding depth of field
As I said before, the control that has the most impact on the depth of field is the aperture. The other two controls you can employ to control depth of field are focal length and camera-subject distance. Essentially, depth of field controls what is in focus. If you are inside the field, you will look sharp. Standing outside the field will make you appear blurred. If you want to be sharp – stay in the field!
Shallow depth of field—A shallow depth of field means that only a small portion of the picture is in focus. This is usually accomplished by using wide apertures.
Great depth of field—A great depth of field means that a large portion of the picture is in focus. The image below uses a relatively close aperture, which is achieved by using the short focal length of the point-and-shoot camera.
Controlling depth of field
The role of aperture
Bigger apertures (small f-stop numbers) tend to provide a shallower depth of field. That means that if you open a wide aperture (say f/1.8), you will have a narrow location in your image that is focused. If you set your aperture to a small value or large f-stop numbers (like f/22), you will have a huge focused area.
Here’s a fun fact: depth of field has two parts: a near side that extends from the object to the camera and a far side that extends from the object away from the camera. The far side is twice as long as the near side. But let us go to more practical tips that will help you control the DOF in your images.
50mm f/1.8
50mm f/7.1
The impact of focal length
A longer focal length lens, like a telephoto lens, typically produces a shallower depth of field. This means that less of the scene will be in focus, and this is often used in portrait photography (sometimes taken to the extreme just for fun).
Why does this happen? Think of it like looking through a straw. The narrower the straw, the smaller the field of view. Similarly, a longer focal length lens “narrows” the field of view, making it easier to isolate a specific subject. This isolation often results in a shallower depth of field.
In contrast, a wide-angle lens produces a much deeper depth of field. This means that more of the scene will be in focus even at larger apertures, making it easier to capture everything in the frame. This is why images taken with wide-angle lenses often appear sharp from foreground to background.
Image by dsevilla (aperture = f/5.6, focal length = 300mm)
Image by wisdoc (aperture = f/5.6, focal length = 135mm)
24mm f/5.6
The impact of camera-subject distance
The distance between the camera and the subject also plays a significant role in determining depth of field. Generally, the farther away the subject is from the camera, the deeper the depth of field will be.
Think of it like this: when you’re looking at a distant object, you can see more of the scene in focus than when you’re looking at something close up. This is because the perspective is wider, allowing more of the scene to be in the focal plane.
In photography, this means that objects farther away from the camera tend to have more of their details in focus. This is why landscapes typically have deep depth of field, with even the farthest objects appearing sharp. On the contrary, close-ups, like macro photography, often have a shallow depth of field.
Creative applications of depth of field
Now that we’ve covered the theory, let’s jump into a more applicable part of this article. How do you apply all that you’ve learned about depth of field? This is the knowledge you’ll need no matter the type of photography and the focal length of the lens you typically shoot. So, let’s cover a few genres to give you a general idea and some more examples.
Macro photography
Basically, there are two approaches for taking a macro shot. One, you can use a very small aperture and get a large DOF, which means sharpness all across the image. Or two, use a small aperture and get an artistic blurry effect.
Keep in mind, though, that small apertures will probably require some flash assistance to get more light into the sensor, even if you use a slower shutter speed. This is especially true for things like bugs, where a tripod and a longer exposure won’t do the trick because those critters won’t stand perfectly still. Pick your flash and make sure you diffuse it well.
Image by mdezemery (aperture = f/18, focal length = 35mm)
Helios 58mm + Raynox DCR-250 adapter, f/2.8
Portrait photography
Although photographers often rely on shallower DOF and longer lenses, the truth is that you can take portraits with any depth of field and any lens you desire. Still, there’s one rule that most of us seem to stick to: always keep both eyes sharp. Eyes are the windows to the soul and they will capture the viewer’s attention, so don’t have them unsharp.
The image below was shot with a very shallow depth of field. It created a nice bokeh and looks good because both eyes are sharp.
Image by perryge (aperture = f/1.8, focal length = 50mm)
Landscape photography
When shooting landscapes, photographers often use a smaller lens aperture along with setting the lens at its hyperfocal distance. What the hell is that you may wonder? Don’t be alarmed; hyperfocal distance is simply the focus point that you focus your camera on and get sharpness from across the focal plane. We’ll get there in a second!
Image by The International Rice Research Institute (aperture = f/10)
Practical tips and practicing
Calculating hyperfocal distance
See, I promised we’d cover this topic in a second. 🙂 By focusing on the hyperfocal distance, you can maximize the amount of your scene that appears sharp, and it’s extremely useful to know for landscape photographers.
There is a manual method to calculate hyperfocal distance called the double-the-distance method. It involves estimating the distance to your closest subject, doubling it, focusing on that point, and adjusting the aperture as needed. Thankfully, nowadays, we have calculators that we can install on our phones. You can use PhotoPills or Hyperfocal Distance Calculator, create custom charts based on your camera’s sensor size and lens focal lengths, and let them calculate the distance for you.
Several factors influence hyperfocal distance, including aperture, focal length, and sensor size. A wider aperture (smaller f-number) results in a shorter hyperfocal distance, as does a shorter focal length (wide-angle lens). Larger sensors also tend to have shorter hyperfocal distances.
This was merely a brief overview, and I suggest you visit this article to learn a whole lot more about hyperfocal distance.
Depth of field self-assignment: pattern breaker
Finally, here’s an assignment for you to practice a bit.
Arrange things in a pattern, or find a pattern in your surroundings—windows, bookshelves, bridges—they all make good patterns.
Try to take several pictures of the same pattern several times. For each series of shots, change one parameter:
Keep the aperture and framing of the picture unchanged, and take a series of pictures by changing the zoom/focal length.
Don’t change the zoom/focal length and framing of the picture and take a series of pictures changing the aperture only.
Keep the aperture and zoom/focal length unchanged and take a series of pictures changing the framing, each time making the center of the image closer to you.
Compare the three series you took. Which control makes the most significant impact on depth of field?
FAQ
Is it possible to get a shallow depth of field with a small sensor? Yes, it’s possible to achieve a shallow depth of field with a small sensor. While larger sensors are often associated with a shallower depth of field, it’s not the sensor size itself that’s the determining factor. The key factors are aperture, focal length, and subject distance. Using a wide-aperture lens, getting closer to your subject, and using a longer focal length can create a shallow DOF even with a small sensor, resulting in beautiful bokeh effects. How does shutter speed affect depth of field? Shutter speed does not directly affect depth of field. Depth of field is primarily determined by aperture, focal length, and subject distance. However, there’s an indirect relationship: if you need to use a slower shutter speed due to low light, you might need to widen the aperture to compensate. This wider aperture, in turn, can lead to a shallower depth of field. So, while shutter speed doesn’t directly influence depth of field, it can indirectly affect it through its relationship with aperture. Which of the 3 pillars of exposure controls the depth of field? The aperture is the pillar of exposure that controls the depth of field. The wider the aperture (smaller f-number), the shallower the DOF, meaning less of the image will be in focus.
