February 9, 2019

4 Factors of Depth of Field That You Should Know About

This 4-minute primer will take the guesswork out of achieving different depths of field.

The area of an image in which elements are sharply in focus is known as depth of field and it can be used in many ways to make your shots look and feel the way you want them to.

Shallow depths of field are great for interviews and close-ups, allowing your subject to be in focus while the foreground and background blur and swirl with beautiful bokeh, while deep depths of field are useful for landscapes and wide shots, capturing your entire scene with crisp sharpness so your audience can appreciate every detail.

For beginners, choosing their desired look might be simple, but knowing how to adjust their camera settings may not. In this video, Kellan Reck explains the three factors that play a role in achieving different depths of field and we'll go a bit more in-depth on each one, as well as how you can use depth of field to tell more dynamic visual stories.

What is Depth of Field

Believe me, understanding what depth of field actually is is a whole lot easier than explaining what it is. I'll take a stab at it without relying on Wikipedia or some official definition. Here we go:

Depth of field is essentially the distance between the nearest in-focus area and the furthest in-focus area in your shot. When that distance is short/narrow/small, it is known as "shallow depth of field" and your foreground (everything in front of your main subject) and background (everything behind your main subject) appears out of focus, while your main subject appears in focus. When that distance is long/wide/large, it is known as "deep depth of field" and your foreground, mid, and background appear in focus.

Credit: Photography Life

Factors that Affect Depth of Field

Once you decide on what kind of depth of field you want to achieve, you'll need to know how to achieve it. Don't worry, newbies, it's really not very complicated. But before we dig into the three main factors at play, understand that each of these factors have affects beyond depth of field, and adjusting them might result in changes to your exposure, angle of view, and other things.

Aperture

First of all, what the hell is aperture? Well, it's the opening of your lens' diaphragm and it's where light passes through into your camera body until it eventually reaches the camera's sensor. (Then magic happens and stuff and an image appears.)

Now, make sure to absorb this little piece of information into your brain because it's weird: the size of the opening is represented in a value called an "f-stop"; the smaller the opening, the larger the f-stop, the larger the opening, the smaller the f-stop

The larger the f-stop, the deeper your depth of field is going to be. Conversely, the smaller the f-stop, the shallower your depth of field is going to be.

Keep in mind, though, that adjusting your aperture will also affect the amount of light that enters your lens, resulting in underexposed (really dark) or overexposed (really bright) images.

If you want to open up your aperture to get a nice shallow depth of field, a lot of light is going to come in and potentially overexpose your image, so you may need to adjust other camera settings, like shutter speed or ISO, or use a neutral density filter (basically sunglasses for your lens). 

If you want to stop down (increasing the f-stop/making the opening smaller) to get deep depth of field, less light is going to come in and potentially underexpose your image, so you may need to adjust your shutter speed, ISO, or add more light to your scene. (I'd pick that last option if you can, so you don't lose image quality.)

Distance to Subject

How near or far your camera is to your subject will affect your image's depth of field.

The nearer you place your camera to your subject, the shallower your depth of field is going to be. The further away you place your camera from your subject, the deeper your depth of field is going to be.

Focal Length

You know those numbers on the side of your lens followed by "mm"? Yeah, that's your lens' focal length. Focal lengths range from the widest wide angle (28mm or lower) to super-telephoto (300mm or higher).

The higher your focal length, the shallower your depth of field is going to be. The lower your focal length, the deeper your depth of field is going to be.

However, it's important to know that the focal length of a lens will affect your images beyond the depth of field. Wide angle lenses have lower focal lengths and will give you a deeper depth of field, but will also increase your angle of view, so you'll be capturing more of the scene in front of you. Telephoto lenses have higher focal lengths and will give you a shallower depth of field, but will also decrease your angle of view, so you'll be capturing less of the scene in front of you.

The Importance of Depth of Field in Storytelling

Now that you know how to achieve different depths of field, it's supremely important to know why you're doing so in the first place. Why? Because these looks affect the way your audience interprets not only the individual shot but also the scene entirely. Let's take a look at a few reasons why you might want to use different depths of field.

Shallow Depth of Field

Because shallow depth of field can render very little of your shot in focus, it does a great job at isolating your subject from the background. Why might you want to isolate your subject?

Well, maybe whatever your subject is is very crucial to the scene, whether it's a prop (gun, bag of money, a wedding ring, etc.) that carries a lot of emotional or narrative significance or a character that is communicating or doing something important. Maybe you want establish intimacy. Maybe your scene calls for a bit of romance, fantasy, or a general distortion of reality.

You can use shallow depth of field to very easily draw your audience's attention to whatever you want, from key moments in the plot to the denouement of an emotional arch. A good example of this (and there are a lot of them) is "The Box" scene in Se7en when Mills (Brad Pitt) has just learned John Doe (Kevin Spacey) has murdered his wife and placed her severed head inside the box he has just been delivered.

'Seven' (1995)

Deep Depth of Field

There's a strange misconception that shallow depth of field is somehow more "cinematic" than deep depth of field...and I mean, that might be due to the fact that amateur video and home movies are often captured with as much in focus as possible. But don't believe this! Deep depth of field can be extremely beautiful and communicate many interesting and valuable things to your audience.

In fact, one of the most famous shots in cinematic history is Gregg Toland's deep focus shot from Orson Welles' Citizen Kane. What does this look do for the scene? It essentially communicates that the actions occurring in the background are just as important as, or at least offer commentary on or context to, what's happening in the midground. This brilliant shot is multi-layered, complex, and economical visual storytelling.

'Citizen Kane' (1941)

Deep depth of field works great for sweeping landscapes, action sequences, and scenes in which the location itself carries narrative or emotional importance to the story. It also creates a feeling of isolation if you throw your character in the mix. Think of the gorgeous deep focus shots in No Country for Old Men.  After finding and keeping $2 million dollars in the desert after a botched drug deal, Llewelyn Moss (Josh Brolin) is pursued by a group of men, as well as hitman Anton Chigurh (Javier Bardem), in order to retrieve the money.

The deep focus shots help communicate several things to the audience.

  • The sprawling, open landscape leaves Moss with nowhere to hide.
  • The film is an homage to the western genre.
  • There isn't any romance in brutality and violence. It's real and almost inevitable.

'No Country for Old Men' (2007)
'No Country for Old Men' (2007)
Hopefully, now you not only know how to achieve different depths of focus but also why you might choose one over the other. Depth of focus isn't just a way to make your images look "more cinematic." It can have a huge narrative and visual impact on your story, one that will surprise, excite, and affect your audience in ways you might've never thought it could.

So, the next time you set up a shot for a project, ask yourself how you can use depth of field to communicate to your audience on a deeper, visual level.     

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