It has become one of Apple’s main selling points. But did you know what distinguishes a Retina screen from a “traditional” screen?
Retina, Super Retina or more recently Liquid Retina, these terms have been used for more than a decade without knowing where they originated from or what they really mean. They equip the iPhone, iPad, iMac and MacBook, but understanding the principle and operation is very important.
It was at WWDC in 2010 that Steve Jobs presented the concept of the Retina display for the first time. A completely new and unheard of term at the time (since trademarked by Apple), English translation of retina. And for good reason, Jobs puts forward a screen whose resolution is high enough so that the human eye cannot notice the pixels in the screen. Where the human eye can notice pixelation up to 300 pixels per inch (ppi), the first Retina display hits … 326 ppi. Thus, 30 cm from the screen, the eye would be unable to perceive the pixels of the new iPhone.
Below: the non-Retina screen of the iPhone 3GS.
It was with the iPhone 4 that Apple introduced the Retina display. An image quality supposed to considerably improve the quality of reading and the visual comfort of consumers. The feeling provided by a Retina screen must be the same as on paper. Text and images should look like they’re printed, not made up of pixels.
And to do this, Apple must significantly improve the screen that equips its iPhone. Its latest model, the iPhone 3GS, has a 3.5-inch LCD panel with a resolution of 480 x 320 pixels, or 163 dpi. A low pixel density, yet legion at the time, which will be swept away out of hand by the Retina quality. “Once you’ve used a Retina display, you can never go back to anything else”then launched Jobs at the WWDC.
The iPhone 4 is, for its time, impressive. Its 3.5-inch screen reaches a resolution of 960 x 640 pixels, four times higher than that of the iPhone 3GS. Jobs’ bet is therefore won, since the pixel density reaches 326 dpi and allows the user to consult his iPhone without straining his eyes. Steve Jobs believed that once the pixels were no longer visible, the images would become as detailed as in real life.
A long scientific analysis of Apple
We will avoid going too much into the technical details since they are very complicated and specific, but you should know that everything depends on the angular resolution, i.e. the ability of the eye to distinguish details according to a distance and the resolution of ‘screen.
Considering that the human eye, having a vision of 10/10, no longer distinguishes pixels from 300 dpi at 30 centimeters away, the angular resolution must be greater than or equal to 63 pixels per degree (ppd). Admittedly, we generally look at the screen of our iPhone from less than 30 centimeters away, but the majority of humans on Earth do not have 10/10 vision in each eye. So an angular resolution of 63 ppd as calculated by Steve Jobs would be sufficient. The Retina screen of the iPhone 4 reaches 68 ppd.
In other words, and as astronomer Phil Plait explained following the announcement at WWDC, “if you have a perfect view, one meter away, the iPhone 4 pixels are resolved. The image will look pixelated. If you have average eyesight, the picture will be perfect.”
Retina variants
But all these calculations were valid 13 years ago. Apple has since developed several variants of the Retina, dramatically increasing dpi and dpi, presumably to accommodate people with 10/10 vision in each eye.
The name Retina remained, but was decked out with another word to make the term even more catchy. Super Retina, Liquid Retina, Liquid Retina XDR. But what do they mean?
- Retina HD (2014): with the iPhone 6 and 6 Plus, Apple goes from a 1,136 × 640 screen to a 1,334 × 750 screen, or even 1,920 x 1,080 with the large model.
- Super Retina HD (2017): the iPhone X has a Full HD+ screen, a resolution of 2,436 x 1,125 pixels, but above all an OLED screen instead of an IPS LCD screen.
- Super Retina XDR (since 2019): OLED display features extreme dynamic range (1,000,000:1). XDR stands for Extreme Dynamic Range.
- Liquid Retina (2018): With the iPhone XR and iPhone 11, Apple is reverting to an IPS LCD screen instead of the more expensive OLED.
- Liquid Retina XDR (since 2021): On the iPad Pro and MacBook Pro, Apple has not yet switched to an OLED screen. We therefore remain on an IPS LCD reaching an extreme dynamic range of 1,000,000:1.
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