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Why high resolution screens matter for Apple's iPad 2

Substantiated rumors of the next generation iPad using a vastly higher resolution 2048x1536 display are drawing some to question why the iPad would even need such a dense pixel count, which is much higher than even Apple's 17 inch MacBook Pro. The answer relates to resolution independence.

Understanding why Apple is expected to increase the next iPad's resolution beyond that of its existing high end notebooks requires a look at how screen resolutions and pixel densities have impacted the history of desktop computing, and why the company's iOS devices stand out as different.

Using higher resolution to increase display area

As screen resolutions have increased with the pace of technology, computers have historically used that new resolution to show more desktop real estate, packing in more sophisticated toolbars and drawing more windows on the screen, each providing a potentially larger, full sized view of the documents they contain.

When Apple released the original Macintosh in 1984, it delivered a resolution of 512x342 on a 9 inch monochrome screen just slightly smaller than today's iPad. The Mac's resolution was significantly higher than the 320x200 CGA resolution common on IBM PCs of the day, but also delivered another unique feature: square pixels.

While the rest of the PC industry was aiming at delivering color graphics for games and separate text-only modes for business apps like word processing, Apple delivered a high resolution black and white display with square pixels because this allowed the Mac to deliver a sharp, accurate screen capable of supporting a consistent, mouse-based user interface of windows and pull down menus, with easily readable text in any font face or size.

Other graphical desktop operating systems, including the Amiga, Atari ST and Apple's IIGS, used non-square pixels, which enabled them to use cheaper TV-like displays but gave their desktop a stretch appearances and distorted the relationship between documents on screen and in print. PCs began to adopt VGA as a square pixel standard only in the late 80s and early 90s.

Apple's crisp graphical user interface has continued across the last three decades, incrementally taking advantage of new display resolution technology to simply expand the Mac, and later Windows, desktop. Screen sizes have grown too, moving users from the original Mac's 9 inch screen to the 15 to 17 inch displays that became common in the 90s and the 20 to 30 inch displays that desktop systems now commonly use. Even notebooks that sport 17 inch displays are not uncommon today.

Mac and CGA resolutions

When higher resolution becomes a problem

Display sizes are now at the point where they can't dramatically grow without simply becoming unwieldily. The mainstream market for notebooks isn't growing much larger than 15 inches, and instead users are trending toward smaller devices, with netbooks once enjoying a brief surge in popularity, followed by Apple's own introduction of the MacBook Air, which offers the company's smallest notebook screen ever.

The new 11 inch MacBook Air delivers a similar pixel count (1366x768) as Apple's previous 13 inch notebooks, while the 13 inch Air uses the same 1440x900 resolution of the 15 inch MacBook Pros. In turn, the 15 inch Pro now offers a 1680x1050 high resolution option that was, until 2008, the native resolution of the 17 inch model.

As screen sizes incrementally bump up their pixel densities, the most obvious difference to users is that icons, menu bars, window controls and text in the user interface all grow smaller. While that allows for larger documents to be viewed within a smaller screen, it will eventually run into the problem of the user interface being too small to see, let alone easily target with a shrinking pointer that eventually becomes lost in a vast sea of pixels.

Rethinking resolution

As computer screen resolutions grow higher on both large and small screens, far smaller screens on handheld devices are exploding in popularity due to their handheld mobility. When the iPhone was introduced in 2007, the most similar smartphone, LG's Prada, offered a 400x200 screen resolution. Microsoft's Windows Mobile had attempted to scale down the PC desktop to fit within resolutions ranging from the Motorola Q's 320x240 "Windows Smartphone" to more PDA-like "Pocket PC" devices with 640x480 resolutions.

The Palm Treo 700 offered a 320x320 screen, opting for a simpler user interface rather than trying to replicate the desktop as Microsoft had with Windows CE. Both continued to use a similar stylus-based input system, which duplicated the role of the mouse in selecting text and targeting buttons and other user interface elements.

Apple's newly rethought user interface for the iPhone offered a different take on small display resolutions. The company abandoned its own concept of a desktop with windows, driven by a mouse pointer (or similarly pixel-accurate stylus), and instead focused the user interface on the much less accurate but far more natural direct touch of users' fingers.

Instead of small window controls and scroll bars, the iOS used large buttons and flickable scrolling lists of items (often arranged in columns of options reminiscent of NeXT's column view file browser, albeit showing one column per screen view at a time) in order to make the most natural use of its 3.5 inch, 480x320 display.

Unlike the Mac desktop, which defined an inch as being 72 pixels and simply grew to consume the increased area offered by higher resolution monitors as they became available, the iPhone's user interface was designed to be resolution independent, defining the whole screen as a fixed number of pixels in an abstract sense.

When Apple introduced iPhone 4 and its 960x640 Retina Display, it didn't display more of the interface at once; it simply sharpened the existing interface to the point where individual pixels became invisible.

Windows Mobile and iOS UI

On page 2 of 3: Focusing on interface resolution, not screen resolution.