Retina Display Explained: How Apple Perfected Screen Clarity With Unseen Pixels

Retina Display is the name for the high-resolution screen technology Apple uses on various models of the iPhone, iPad, and other Apple products. It was introduced with the iPhone 4 in June 2010. Read on to understand what Retina Display is, how it's different from other screens, and what products use it.

What Is Retina Display?

Retina Display smooths the jagged edges of the screen's pixels and makes images seem more natural. Retina Display gets its name from Apple's claim that screens made using the technology are so sharp that it's impossible for the human eye to distinguish the individual pixels that make up the screen.

The benefits of the technology are particularly visible when looking at text. On Retina Display, the curved edges of fonts are substantially smoother than on previous display technologies.

A Retina Display's high-quality images are the result of several factors:

• A high density of pixels that make up the screen.
• A high contrast ratio that creates brighter whites and deeper blacks.
• In-Plane Switching (IPS) technology that improves the angles from which the screen can be viewed.
• Chemically treated glass over the screen and LED backlighting improve the quality of the image.

The Two Factors That Make a Retina Display Screen 

There's no single answer to the question "what is Retina Display resolution?" For example, not every device with a resolution of 960-by-640 pixels has a Retina Display, even though that's the resolution of the iPhone 4, which has a Retina Display screen. Instead, a screen has to meet two criteria to qualify as a Retina Display screen: pixel density and the distance from which the user views the screen.

Pixel Density

Pixel density is how tightly packed the screen's pixels are—the greater the density, the smoother the images. Pixel density is measured in pixels per inch (PPI), which is how many pixels are present in one square inch of screen. This metric is based on a combination of the device's screen resolution and its physical size.

The iPhone 4 had 326 PPI due to a 3.5-inch screen with a 960-by-640 resolution. This spec was the original PPI for all Retina Display screens. That changed as later models were released. For example, the iPad Air 2 has a 2048-by-1536 pixel screen, resulting in 264 PPI. That, too, is a Retina Display screen. This is where the second factor comes in.

Viewing Distance

Viewing distance refers to how far away users typically hold the device from their faces. For example, the iPhone is usually held relatively close to the user's face, while a MacBook Pro display is seen from farther away.

This matters because the defining characteristic of a Retina Display is that the human eye can't distinguish the pixels. Something that's seen up close needs a greater pixel density for the eye not to see the pixels. Pixel density can be lower for displays viewed at a greater distance.

Other Retina Display Names

As Apple has introduced new devices, screen sizes, and pixel densities—and made improvements to the display technology—the company began to use other names for different Retina Display types. These include:

• Retina Display: Used on the iPhone 4, among others.
• Retina HD Display: Used on the iPhone 6 Plus and others.
• Retina 4K Display: Used on the 21-inch iMac.
• Retina 5K Display: Used on the 27-inch iMac.
• Retina 6K Display: Used on the Pro Display XDR screen.
• Retina LTPO Display: Used on the Apple Watch Series 6.
• Super Retina HD Display: Used on the iPhone X and iPhone XS.
• Liquid Retina HD Display: Used on the iPhone XR and iPhone 11, among others.
• Super Retina XDR Display: Used on the iPhone 11 Pro and Pro Max and iPhone 12 series.

Apple Products With Retina Display

Retina Displays are available on the following Apple products, at the following resolutions and pixel densities:

iPhone

* in inches for all charts

iPod Touch

iPad

Apple Watch

iMac

MacBook Pro

MacBook