Learn more about this important concept that can aid composition and storytelling in both photography and cinematography.

1. What does depth of field refer to?

Depth of field: Refers to how much of a scene appears acceptably in focus

Depth of field (DOF) describes the distance between the nearest and furthest points from the camera that appear to be acceptably in focus (“in-focus area”).

You can think of it as like your lens projecting a huge glass container parallel to it. The glass container changes position depending on where you place your focus, but it is always parallel to the lens. Objects inside this glass container appear sharp and in-focus, whereas those outside it appear blurrier the further they are from the container.

The size (depth) of the depth of field can be controlled using:

1. Aperture
2. Focal length
3. Image sensor size
4. The camera’s distance from the subject

Changing factors 2-4 will also change the framing and perspective, affecting composition. For more details and examples, keep scrolling.

Shallow focus
If the glass container is thin, we say the depth of field is “shallow” or “narrow”.  Only a small part of the scene is in focus while everything else in front of and behind is blurred (turned into bokeh). This is also known as a shallow focus shot.

Deep focus
If the glass container is so thick that most of the scene is in acceptable focus from the front to the back, we say that the depth of field is “large” or “deep”. This is known as a deep focus shot.

Related topics:
Camera Basics #1: Aperture
Lens Basics #3: Creating Bokeh

2. 5 rules for controlling the depth of field

5 rules for controlling the depth of field

1. The larger the aperture (smaller f-number), the shallower the depth of field

At f/1.8, only some of the green and red sticks are in focus. Everything else is blurred out. When we increase the depth of field by using a higher f-number, more of the scene is in-focus.

Consider: Depth of field when shooting moving subjects

When shooting moving subjects, consider using a larger depth of field so that the subject is more likely to stay in the in-focus area even as it moves around. The easiest way to do it without changing the composition is to narrow the aperture (use a larger f-number).

If you prefer to use a shallow depth of field, Canon’s reliable deep learning-based AF tracking should help keep the subject in focus. Here are 5 Tips for Better Subject Detection and Tracking to increase your keeper shots!

2. The nearer your lens to the subject, the shallower the depth of field

The lens was closer to the fence in the first image. This also makes the background closer (and look larger), magnifying the out of focus blur.

Tip: Also notice how when we step away from the subject, the framing and perspective changes although the focal length is the same.

3. The longer the focal length, the shallower the depth of field

These two images were captured from the same shooting position by zooming in from 35mm to 105mm. The magnification from the longer focal length makes the depth of field look shallower. The opposite is true, too: wide-angle lenses naturally provide a deeper depth of field even at wider apertures.

That’s why full-frame cameras create “more intense bokeh” and APS-C and compact cameras give more depth of field. Sensor size affects the focal length you use to achieve a given field of view. (Learn more in: Full-Frame vs APS-C Camera: Which Should I Choose?)

4. The depth of field is shallower than usual during close-up and telephoto shooting

If you are shooting close-ups or using a telephoto lens, you would have to use a narrower aperture than usual to get a deeper depth of field. If you are shooting stills of a static subject, you might even want to consider focus bracketing and depth compositing to achieve the desired depth of field.

Close-up at f/1.8
Shot on the EOS R6 Mark II + RF35mm f/1.8 Macro IS STM

Only a thin strip of fabric is in focus in this close-up shot. That’s why focusing can be so challenging during close-up and macro photography!

Telephoto @ f/11
Shot on the EOS R + RF600mm f/11 IS STM

We usually need a very wide aperture to get a blurred background but at 600mm, the focus is shallow even at f/11.

5. Camera angle matters

Remember our “glass box” of focus? Unless you are using the tilt function on a tilt-shift lens, it is always parallel to the image sensor plane (and your lens’ tip).  If you tilt your camera or shoot a subject from a different angle, you can change what is inside the “glass box” without changing the depth of field.

Here’s what happens to the gate from the previous examples when we shoot it from different angles.

f/1.8 - Head on

The entire white gate is in focus even at f/1.8.

f/1.8 - Diagonal

Just one of the metal posts is in focus. To get more of the posts in focus while shooting from this angle, we would need a larger depth of field.

3. Useful camera setting: Depth of field preview

Useful camera setting: Depth of field preview

By default, your camera previews the exposure (image brightness) but not the depth of field. That’s related to full-aperture metering, where regardless of your aperture setting, the aperture blades are always fully open until right before you take the picture, allowing them to take in as much light information as possible. What you see in your rear LCD screen or electronic viewfinder is a simulation from the image processor.

There are two ways you can preview the depth of field.

Option 1: Always preview the depth of field

The camera will close the aperture blades according to your aperture setting even when metering. It might affect focusing especially in low light situations as less light enters the camera.

Option 2: Press a button to preview the depth of field

The camera closes the aperture blades temporarily when the assigned button is pressed. 

Some cameras like the EOS R6 Mark II have a default depth of field preview button, but you can reassign the function to another button. On other cameras, you will have to decide which button to use.

4. How depth of field affects visual expression

How depth of field affects visual expression

Our eyes tend prioritise objects that appear sharp and in-focus. Therefore, controlling the depth of field is an important skill that can help us achieve better pictures and even help with storytelling. This applies to both photography and cinematography.

1. It determines how much of our subject looks sharp

In both images, we placed the focus point on the tip of the strawberry. At f/1.8, everything else is out of focus and blurred out; at f/16, everything else is clearer.  (We kept the same focus point for easier comparison. In practice, shifting the focus point to the cream would help us get more in focus with a slightly wider aperture.)

2. It can set the subject of the image

Know this: When more objects are in focus, it also means more potential distractions. You will have to consider the composition more carefully.

Also see:
Composition Basics (2): Main and Secondary Subjects; Triangles

3. It can determine how much contextual detail is shown

A shallow depth of field blurs out (“simplifies”) the leaves in the background and foreground so our attention is mainly on the flower. A larger depth of field makes us notice the leaves that surround the flower too.

Cinematography: Focus transitions as an expressive tool

In video and filmmaking, changes to the depth of field and focus point are recorded. You can use these transitions creatively to determine how the story unfolds. That’s also a way to add movement to your shot without camera movement!

For example, slowly increase the depth of field of a shallow focus shot to unveil objects in the background, or vice versa:

This may accompany “focus pulling” or “focus racking”, i.e., moving the focus from one object in the frame to another. Focus racking transitions are more obvious when the depth of field is shallow. 

 

Learn more about depth of field and related techniques in:
In Focus: Aperture Settings for Various Scenes
What is the difference between an f/2.8 and an f/4 telephoto zoom lens?
Portrait Photography: 3 Aperture Settings Favoured by Professional Photographers
4 Lens Concepts to Revolutionise Your Photos
How to Create Dreamy, Colourful Portraits with Foreground Bokeh