In video, focus is often thought of as a measure of sharpness. Is the subject “in focus,” meaning, can we see them clearly in the image? That’s just one part of it. There are many types of focus in films and videos, achieved in different ways and for varied effects. Directors and cinematographers use focus as a means of storytelling, conveying the emotion of the scene, but what are the technical aspects you need to understand to achieve these storytelling goals? In this article, we will explain focus, depth of field, focus charts, types of focus, and provide plenty of examples.
What is focus?
In a nutshell, focus is the optimal sharpness or clarity of a subject. Focus is achieved either manually or automatically, as anyone who has picked up a camera can see. Half-press your shutter button and your camera will focus on an object, usually highlighting it in a green box.
What is depth of field?
Depth of field refers to the area of your frame that is sharp or how much is in or out of focus. Depth of field is manipulated by adjusting the focal length of the lens, changing aperture, or physically changing the distance of the subject to the camera. Also referred to as aperture, or f-stop, this measure is how much light the camera lets into the sensor. Camera aperture is responsible for the bokeh or blurring of parts of the frame. Shallow depth of field creates more bokeh while with deep depth of field, more of the subject and background will be in focus. The higher the f-stop number, the deeper the depth of field; the lower the f-stop number, the more shallow or “wide open.”
Types of focus
Deep focus means everything in the frame is sharp and clear. The foreground, mid-ground, and background objects are in focus, giving the frame balance. No one subject is more important than the other. For example, in the Artgrid clip below, you can make out all the details of the background, a garden, and the foreground subjects, a mother and two children gardening.
Cinematic examples of deep focus can be found in Westerns films such as Once Upon a Time in the West.
Split diopters can be used to create deep focus. A split diopter is a lens attachment that allows for focus on multiple planes. This half convex glass causes a split down the middle of the frame making one-half nearsighted and the other farsighted. When used correctly, this mind-bending technique can lend to a sense of juxtaposition or fantasy in a film.
Shallow focus is achieved with shallow depth of field, meaning the subject is in focus while the background is out of focus, or blurry. In shallow focus, the plane of focus, meaning the space around your focal point that is sharp, is relatively small while the larger background area is out of focus, or bokehed. Shallow focus is used to direct the eye towards something specific and also to convey emotion. You can create shallow focus by decreasing the f-stop or using “faster” aperture settings, bumping up the focal length, or altering the distance of the camera to the subject. Camera ISO factors into shallow focus if you’re shooting in low light, as higher ISOs can help achieve this but may also introduce grain.
In the example below, a woman is in sharp focus while the ocean in the background remains out of focus while the camera pulls away.
A famous example of shallow focus in film is in Baz Luhrmann’s Romeo + Juliet where the star-crossed lovers pledge their devotion to one another.
Rack focus means the camera racks or changes focus from one subject to another. One object is sharp while another is out of focus, then the focus is inverted. Rack focus moves the eye from point A to point B and can be used to shift attention. For example, in the Artgrid clip below, you see a child’s hand in shallow focus as they push medical equipment in a hospital while the background is out of focus, but then the focus changes to a clown juggling.
To achieve perfect rack focus, you’ll need to rehearse with your actors and give them marks or exact positions. Precise rack focus is often achieved when the camera is stationary and with the aid of a focus puller. The focus puller is a member of the crew whose entire job is to adjust focus at different points in the shot while the cinematographer focuses on operating the camera.
You can see a great example of rack focus in this scene from The Host, the 2006 sc-fi film by Bong Joon Ho who’s 2019 film Parasite won 4 Academy Awards (among many other awards). Here the focus changes from the hero who tries to escape the hospital by blending in with the other patients to his accomplice behind him, to the nurse that spots him in the crowd.
Different from shallow focus, soft focus gives framing a dreamy quality by adding a glow around an object. Soft focus indicates that the sequence may be fantasy or dream; it’s not entirely real. It adds a trippy quality to the storytelling and is associated with films from the twentieth century.
Soft focus was also used in vintage films almost exclusively on female characters, making the actors look less sharp and more “feminine.” Watch this video for a host of examples of soft focus in vintage filmmaking and take a look at this Artgrid video below as well.
This soft blur can be done DIY by smudging the lens with Vaseline or putting a thin piece of gauze over the lens. Pro options for achieving soft focus include attaching a diffusion filter to your lens or even using a specialized cinema soft-focus lens.
If you’ve ever used social media filters, you’ve seen tilt-shift before. Tilt-shift has the effect of making subjects look like miniatures by dramatically de-focusing parts of the frame. This kind of focus is achieved by controlling perspective, tilting or shifting the lens in relation to the focus. Tilt-shift can be done in post by simply blurring a photo or video clip, but there are also specialized tilt-shift lenses. It’s often used in photography of architecture, but can be seen in this sequence from The Social Network.
What is a focus chart and how to use it
A focus chart can be a valuable tool to achieve very precise shallow depth of field. The chart is basically a target with multiple zones to focus on. The focus chart is used to calibrate lenses and/or test the autofocus of your camera. The focus chart can be used for ensuring your camera’s focus is exactly where you want it, so this works best when you have total control over the subject such as in a studio.
Learning different types of focus is essential to good storytelling and meaningful camera work. Understanding which types evoke certain emotions as well as how to achieve the technique for doing so will elevate your filmmaking exponentially, whether you are shooting on an iPhone or an Arri cinema camera!