How Does the Dolly Zoom Work?

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Welcome to How did you do that? – A bimonthly column that unpacks moments of movie magic and celebrates the tech assistants who pulled them off. This entry explains the in-camera effect known as “dolly zoom”.

Even if you’re unfamiliar with its name or how it works, as a movie buff, you’ve probably seen one Dolly zoom. And if you’ve seen a dolly zoom, you know its performance can’t be denied.

Dolly zooms are an overwhelming and unforgettable effect. If you’ve ever seen a shot where a background is impossible to warp, expand, or narrow around a character, you’ve seen a dolly zoom. If you’ve ever seen a shot with a sudden distortion of perspective that zeroed the subject, you’ve seen a dolly zoom. And if you’ve ever seen jawYou saw a dolly zoom.

For all their audacity, dolly zooms can achieve some of the most powerful visual storytelling moments in the cinema.

They can create a sudden feeling of discomfort and disorientation. They can signal strong and scary emotional states like tension, revelation, euphoria, and fear. They can make the floor feel like the floor is falling out from under you or the walls are closing. You can reduce the distance or steer the background into the unknown. When used on purpose, like the best effects, they are so much more than a visual boost.

Dolly zooms are used boldly and can be beneficial to the brain. And after scraping your astounded gray matter off the floor, you might be wondering: why did that look so strange? How did they manipulate the space like that? Did the filmmakers use a green screen? Was it rear projection? What exactly is going on here?

How did you do that?

To make it short:

Dolly zooms are an in-camera illusion created by combining a wide-angle zoom lens, steady zoom, and dolly. By dolly and zooming in opposite directions, the foreground elements appear to stay the same size while the background appears to squeeze or stretch.

Long story long:

Before we start, I want you to humor me and imagine yourself looking down a hallway at a window. The further away you stand from the window, the less the outside world is visible to you. Well two things:

  • From this distant position when you take out a camera and zoom in It would appear bigger on the window. But the amount of what you could see outside of it would stay the same.
  • Again from this distance, if you physically approach the window (mimicking a Dolly-in), the closer you get, the more of the outside world you could see.

That was a very basic exercise. But those are the basic principles of the Dolly and the Zoom. And we have to understand them to understand how the dolly zoom works. Before we go any further, I’ll assume most people are familiar with the subject of zoom. However, this may not apply to dolly shots. Dolly shots refer to a shot captured by a camera mounted on a trolley that is usually on rails. The two dolly movements that concern us are when the camera moves towards (dolly-in) and away from (dolly-out) the subject. In other words: zoom in, dolly shots move.

To recap, if you zoomed out or out in the same spot on our imaginary hallway and looked into your viewfinder, you would see an identical image. When you zoom in from this position, the subject (also known as a window) is enlarged. If you went in instead you would create a visual phenomenon known as “perspective distortion. “Perspective distortion is the apparent spatial distortion of an object and its surroundings due to the relative size of near and distant features. In other words, it is the phenomenon that objects look different when a camera’s relative distance to them changes.

The dolly zoom combines all of these basic principles with trippy results. To understand how this works we need to unpack the two traditional types: (1) Dolly-out and zoom-in and 2) Dolly-in and zoom-out.

With both types, the camera focuses on a single point in space (usually the subject). The zoom ensures that the frame section remains relatively even. And the opposite dolly / zoom techniques cancel out the visual movement of the focus. This means that the foreground elements remain roughly the same size throughout the entire recording. Meanwhile, everything that is not in focus becomes distorted as the perspective is constantly changing. This creates the effect we associate with dolly zoom.

On the whole, dolly zooms look weird because they literally break our brains. The human visual system uses size and perspective cues to determine the relative size of objects. To see a change in perspective without changing size is, of course, unsettling.

What the distortion looks and feels like depends on which dolly zoom you are using. When the camera Dollys-out and zooms-inThe longer focal length creates increased magnification and a narrower angle of view, which flattens the image. This makes it look like the background is closing around the foreground subjects. That’s what happens in this diner scene in Goodfellas and this anxiety attack in hate::

When the camera Dollys-in and zooms-out The focal length is shortened, creating a lower magnification and a wider angle of view, which causes the image to be curved. This gives the look of the background stretching around the subject. That’s what happens in this shot of poltergeist and this shot from Jaws:

Dolly zooms can also be helpful in telling the difference between a Telephoto lens and a Wide angle lens. Let’s go back to Jaws’ dolly zoom and compare how it starts and how it ends. When recording starts, the subject (Roy Scheider‘s Brody) is far from the camera. We can see less of the background because the lens is focused on a smaller part of what is in front of it. If the camera moves forward while zooming out, the focal length will change. This causes Brody’s face to stretch unnaturally while more background becomes visible to us. This is effectively a shift between a telephoto lens and a wide angle lens. And switching from one to the other makes an emotional point. In this case: a terrible, stomach-twisting realization that a giant shark is eating a child.

Jaws Dolly Zoom Telephoto to wide angle

The difference between the two types of dolly zooms (expansion or contraction) leads to very different emotional reactions for the viewer. The contraction effect closes the world around the subject, provoking paranoia and impending danger. You can see this at work when Frodo first perceives the Nazgûl The Lord of the Rings: The Fellowship of the Ring. By reducing the road distance, the camera implies that this enemy is rapidly approaching and that even forests have retreated in its presence.

Community of the Ring of Nazgul

If you perform the opposite movement (dolly-in, zoom-out), the world moves away from the subject. This expands the space and can create a domineering sense of isolation and panic. If you’re looking at a scene where a hallway is impossible to extend (as in Poltergeist), you are most likely seeing a zoom in and out cart.

In the end, three factors contribute to the dolly zoom effect: (1) the direction of movement of the camera; (2) the speed at which you dolly; and (3) the focal length of the camera lens. Ultimately, the way filmmakers modulate these factors has a significant impact on how the shot feels.

Poltergeist hallway

What’s the precedent?

For a dolly zoom to work properly, cameramen need a smooth dolly track and a stable zoom lens that can be reliably and precisely controlled. A main reason for this is that the speed of the dolly and the zoom must match so that they can land at the same time. Suffice it to say, in order to create a cinematic dolly zoom, you need the right equipment. This is why it took so long to “invent” the effect at all. Pulling them off is actually quite difficult.

It is generally accepted that the dolly zoom first appeared in a mainstream movie in 1958 Alfred Hitchcockthriller dizziness. In fact, many people know them as the dizziness effect. (The list of pseudonyms is actually very long and includes the trombone recording, the push-pull and the contra-zoom telescope). In Vertigo, Hitchcock uses dolly zooms several times to convey the agoraphobia of John “Scottie” Ferguson (Jimmy Stewart) and, well, vertigo. The dolly zoom conveys feelings of nausea, imbalance, panic and distorted proportions. It’s perfect.

Most people agree that Vertigo put the dolly zoom on the map. But there are some who say it was the first film to use the technique up close. Legend has it that Hitchcock got the idea for the shot after being dazed and passed out at a party. Allegedly this idea trickled away from Rebecca. And as the story goes, Hitchcock turned to Vertigo’s second cameraman. Irmin Robertswho developed the shot.

Whether or not the myth itself is true, the fact remains that the presence of the effect in Vertigo is the culmination of softer zoom lens technology as well as a narrative need. And if an effect named after your movie isn’t reason enough to set a precedent, I don’t know what it is.

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