Sign In

Communications of the ACM


Zoom In, Zoom Out

View as: Print Mobile App ACM Digital Library Full Text (PDF) In the Digital Edition Share: Send by email Share on reddit Share on StumbleUpon Share on Hacker News Share on Tweeter Share on Facebook
vortex image


Get Microsoft Silverlight

Zooming, the ability to move in and out of information to show different levels of detail on a computer display, would seem the most mundane of capabilities. Indeed, zooming in various guises has been possible for at least two decades, and it's the rare application today that does not give users at least a rudimentary zooming ability.

But the story of zoom technology is surprisingly complex. There are many ways to produce a zoom effect, and many of the ideas tried over the years have seemed to hold enormous promise, but have languished, often because the cost to the user exceeds the benefit that the user perceives.

Today innovation lies less in the development of new zoom technologies and more in the application of existing ones. One such application, called ChronoZoom, can seamlessly zoom into a gigantic multimedia database at levels from millenniums to nanoseconds. This kind of deep zooming is an example of what has become known as the "zoomable user interface," or ZUI.

It seems an impossibly ambitious goal: "visualizing the history of everything." ChronoZoom, however, may plausibly enable just that. ChronoZoom is essentially an online interactive timeline using a nonlinear, or variable scale, presentation. At the top of your screen lies a horizontal timeline stretching at the left from the Big Bang 13.7 billion years ago to today on the far right. In between, you might zoom in on a point at 12 billion years ago and watch a video about how dying stars began to create new elements. Or you might zoom in to the year 1300 to learn about the birth of the Ottoman Empire, or to Jan. 24, 2012 to learn about the birth of Princess Athena Marguerite Françoise Marie of Denmark. At any point on this "virtual canvas" you could be presented with relevant photographs, graphs, video, audio, or text. "It could scale down to one nanosecond if we had content for a nanosecond," says Rane Johnson-Stempson, a director at Microsoft Research.

ChronoZoom is an open source system led by the Outercurve Foundation and being built by scientists at the University of California, Berkeley, Microsoft Research, Moscow State University, the University of Washington, and nearly 20 subject matter experts from around the world. ChronoZoom runs on Microsoft's Azure cloud service and uses SQL Azure for storage. It has HTML5 on the front end and some 100 APIs to integrate existing content and software on the back end. ChronoZoom also operates on a variety of platforms, including mobile devices such as iPads, iPhones, Android devices, and Windows Phone.

The problem ChronoZoom and other ZUIs attempt to solve could not be simpler. "There is more information than fits on the screen," says Ben Bederson, a computer science professor at the University of Maryland and a pioneer in ZUI technology. This problem can be overcome by scrolling, linking, searching, and zooming into successively dense representations of the information. All file and Web browsers and image and document editors offer one or more of these capabilities.

But, according to Bederson, the term ZUI has come to refer specifically to those systemssuch as Google Mapsthat provide both spatially and temporally changing views to navigate at different scales, among multiple objects such as text documents, photographs, or entire ensembles such as presentations.

People are attracted to ZUIs for at least three reasons, Bederson says. They are engaging, naturally suited to human visual perception abilities; they are visually rich, offering multiple degrees of freedom; and they are potentially simple, offering the ability to find something in a place, much as you might locate a document on your physical desktop.

Back to Top

The March of ZUIs

Ken Perlin and David Fox, computer scientists at New York University, kicked off the ZUI era in 1993 with a paper titled "PadAn Alternative Approach to the Computer Interface." Pad was "an infinite, two-dimensional information plane that is shared among users," they noted. "Every object occupies a well-defined region on the Pad surface." Users peered into virtual magnifying glasses called portals, which could be moved to any part of the surface the user wanted to look into. Each mouse click instantly produced a view twice or half the size of the previous view.

ZUI technologies appeared in a steady stream after that. A year later, Bederson and James Hollan, then at Bellcore, unveiled Pad++, a successor to Pad that, instead of sudden jumps, would zoom smoothly and continuously when the mouse button was held down. Ensuing ZUIs included CounterPoint, which Bederson introduced in 2001, a Microsoft PowerPoint plug-in that enabled presenters to arrange their slides on a zoomable space. In 2008, a company called Zoomorama introduced a client/server ZUI for zooming images over a network. And in 2009, Microsoft brought out Canvas for OneNote, which offered a zoomable overview of all of a user's notes.

A particularly dazzling ZUI appeared in 2009 in the form of Prezi, a "zooming presentation software," from a Budapest-based company of the same name. Prezi is Web based and features 3D fade-in animation that combines smooth rotations, panning, and zooming in realistic 3D views of slide presentations. Prezi uses Adobe Flash in the browser and the desktop application, and uses native OpenGL, the cross-platform API for 2D and 3D graphics, on the iPad.

While each advance has been based on plausible expectations of user benefits, many ZUIs have enjoyed limited success in the marketplace. Zoomorama closed for lack of business in 2010. And PhotoMesa, a zoomable photo browser developed by Bederson in 2001 that simultaneously offered views of multiple directories of images, did not catch on either. "I used all kinds of tricks to help you organize your images, but in the end it was not a good idea," explains Bederson. "It has this essential problem that its goal was to spatially organize tens of thousands of images. Nobody wants to do that."

PhotoMesa was not the only ZUI to make that mistake, according to Bederson. These ZUIs are based on the observation that people often organize their lives spatially, such as papers arranged on their desks, for example. "But the reality is people don't have 10,000 papers on their desks," says Bederson, who notes the problem is that people's spatial memories do not scale up. "You can't remember the position of 10,000 things. For these kinds of problems, you can't beat visual scanning of a one-dimensional list."

PhotoMesa users found they preferred to use simple programs like Microsoft Windows Explorer or Google Picasa, where files and folders are displayed linearly and sorted alphabetically or by date.

Of Prezi, Bederson says, "It's cool. The first time you see it you say, 'Wow, this will change everything.' But there is little real benefit and a real cost." The cost, he says, comes from the need to sit through animated transitions, each of which takes a small amount of time. "It's a lot of distraction that ultimately annoys people," he says.

But Prezi argues that its mass-market appealit claims to have 12 million usersproves its value. "Any technology misused can be distractingdisjointed video, poorly designed newsletters or intranets, and long wordy emails," says Drew Banks, head of marketing at Prezi. "In general, research tells us that the human brain is far more adept at spatial memory than it is at remembering nonvisual or non-spatially related data."

In any case, ZUIs have proven themselves, says Bederson, and the right approach now for application developers is to choose wisely among existing zoom technologies and apply them correctly. "This was a computer science research topic, with lots of people looking at lots of technologies," says Bederson. "Some of them panned out and some didn't. I'm delighted to see zooming as part of the developer's toolkit, but I don't see it as a research project anymore."

Perhaps not, but the use of deep zooming technology seems likely to increase as applications access ever larger and more heterogeneous databases. "The reason we use the ZUI metaphor is that you don't know what you are searching for unless you know," says Johnson-Stempson. "When you have crazy amounts of data, it's really difficult. The whole point of ChronoZoom is to come across information you have no idea about, then zoom into the details." ChronoZoom includes a rudimentary keyword search engine at present, but developers see zooming as the primary way for users to find information.

"In the field of big history, it is the patterns, cycles, and trends that are most useful," says Roland Saekow, a ChronoZoom project leader at the University of California, Berkeley. "By visualizing all the past, it is possible to browse history, rather than digging it out piece by piece. ZUIs excel at the capability of providing context."

"I think one of the really interesting questions now is how to let the user feel more in control as they navigate these ZUIs," says Saekow. "In the latest build, we have added multitouch support in HTML5. With trackpads and multitouch screens, we find it is less and less necessary to teach users how to zoom in or out. Pinch and zoom on such new surfaces are natural motions. Instead of having to learn that the scroll wheel controls zoom depth, and the mouse controls panning and selection, touch makes it possible to do both at once.

"Ultra-high resolution touch screen displays may make navigation of large-scale ZUIs more intuitive in the future," says Saekow. "Perhaps with the addition of haptic feedback, we can provide users a sense of how far they are zooming, or as they zoom past certain depths, we can provide a tactile feedback. We have also not leveraged sound effects, but with our large zoom jump from a single day to the Big Bang, we have often felt a zoom sound effect might be interesting to add."

Back to Top

Further Reading

Bederson, B.
The promise of zoomable user interfaces, Proceedings of the 3rd International Symposium on Visual Information Communication, Beijing, China, Sept. 2829, 2010.

Cockburn, A., Savage, J., and Wallace, A.
Tuning and testing scrolling interfaces that automatically zoom, Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, Portland, OR, April 27, 2005.

Igarashi, T. and Hinckley, K.
Speed-dependent automatic zooming for browsing large documents, Proceedings of the 13th Annual ACM Symposium on User Interface Software and Technology, San Diego, CA, Nov. 58, 2000.

Johnson-Stempson, R.
hronoZoom Tutorial, Microsoft Research,, March 12, 2012.

Ware, C.
Information Visualization, 3rd Edition, Morgan Kaufmann Publishers, Burlington, MA, 2012.

Back to Top


Gary Anthes is a technology writer and editor based in Arlington, VA.

Back to Top


UF1Figure. A Web-based timeline, ChronoZoom enables users to see the scale of time over cosmic, geologic, biological, and social periods.

Back to top

©2012 ACM  0001-0782/12/12

Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and full citation on the first page. Copyright for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or fee. Request permission to publish from or fax (212) 869-0481.

The Digital Library is published by the Association for Computing Machinery. Copyright © 2012 ACM, Inc.


Benjamin Bederson

Thanks Gary - good article. The following reference is for the recent article I think you intended to cite in the "Further Reading" section - is it my detailed reflection on ZUIs, explaining in more detail where I think their promise lies, what the challenges are, and a number of design guidelines to make them work well.

Bederson, B. B. (2011). The Promise of Zoomable User Interfaces, in Behaviour & Information Technology, Taylor & Francis, Nov-Dec 2011, 30 (6), 853-866.

Displaying 1 comment

Sign In for Full Access
» Forgot Password? » Create an ACM Web Account
Article Contents:
  • Introduction
  • The March of ZUIs
  • Further Reading
  • Author
  • Figures
  • Get Microsoft Silverlight ">