Retina display is a brand name used by Apple for its series of IPS LCD, and OLED displays that have a higher pixel density than traditional Apple displays. Apple has applied to register the term "Retina" as a trademark in regard to computers and mobile devices with the United States Patent and Trademark Office, Canadian Intellectual Property Office, and in Jamaica. On November 27, 2012 the US Patent and Trademark office approved Apple's application and "Retina" is now a registered trademark for computer equipment.
When an Apple product has a Retina display, each user interface widget is doubled in width and height to compensate for the smaller pixels. Apple calls this mode HiDPI mode. The goal of Retina displays is to make the display of text and images extremely crisp, so pixels are not visible to the naked eye. This allows displays to rival the smooth curves and sharpness of printed text and immediacy of photographic prints.
These better quality displays have been gradually released over a number of years, and the term is now used for nearly all of Apple products containing a screen, including Apple Watch, iPhone, iPod Touch, iPad, MacBook, MacBook Air, MacBook Pro, and iMac. Apple uses slightly different versions of the term for these models, including Retina HD Display for iPhone 6 and later versions, and Retina 4K/5K Display for iMac.
Apple's Retina displays are not an absolute standard but vary depending on the size of the display on the device, and how close the user would typically be viewing the screen. Where users view the screen at a closer distance to their eyes, as on smaller devices with smaller displays, the displays have more PPI (Pixels Per Inch), while larger devices with larger displays where the user views the screen further away use fewer PPI. Later device versions have had additional improvement, either counted by an increase in the screen size (the iPhone 6 Plus) and/or contrast ratio (the iPhone 6 Plus, and iMac with Retina 4K/5K Display), and/or more recently with PPI count (iPhone X, XR, XS, and XS Max), thus Apple using the name “Retina HD Display", "Retina 4K/5K Display", "Super Retina HD Display", or "Liquid Retina HD Display".
When introducing the iPhone 4, Steve Jobs said the number of pixels needed for a Retina display is about 300 PPI for a device held 10 to 12 inches from the eye. One way of expressing this as a unit is pixels-per-degree (PPD) which takes into account both the screen resolution and the distance from which the device is viewed. Based on Jobs' predicted number of 300, the threshold for a Retina display starts at the PPD value of 57 PPD. 57 PPD means that a tall skinny triangle with a height equal to the viewing distance and a top angle of one degree will have a base on the device's screen that covers 57 pixels. Any display's viewing quality (from phone displays to huge projectors) can be described with this size-independent universal parameter. Note that the PPD parameter is not an intrinsic parameter of the display itself, unlike absolute pixel resolution (e.g. 1920×1080 pixels) or relative pixel density (e.g. 401 PPI), but is dependent on the distance between the display and the eye of the person (or lens of the device) viewing the display; moving the eye closer to the display reduces the PPD, and moving away from it increases the PPD in proportion to the distance. It can be calculated by the formula
where is the distance to the screen, is the resolution of the screen in pixels per unit length, and is the aperture of a cone having the apex on focus, height , and the base in the eye lens —the optical correspondent to a cone inside the eye having the same base and the apex in the other focus, the fovea. That aperture, which can be measured by visual field tests, varies widely among different human subjects.
In practice, thus far Apple has converted a device's display to Retina by doubling the number of pixels in each direction, quadrupling the total resolution. This increase creates a sharper interface at the same physical dimensions. The sole exception to this has been the iPhone 6 Plus, which renders its display at triple the number of pixels in each direction, before down-sampling to a 1080p resolution.
The displays are manufactured worldwide by different suppliers. Currently, the iPad's display comes from Samsung, while the MacBook Pro, iPhone, and iPod Touch displays are made by LG Display and Japan Display Inc. There was a shift of display technology from twisted nematic (TN) liquid-crystal displays (LCDs) to in-plane switching (IPS) LCDs starting with the iPhone 4 models in June 2010.
Apple markets the following devices as having a Retina display, Retina HD Display, Liquid Retina HD Display, Super Retina HD Display, or Retina 4K/5K Display:
|Model||Marketing name||Screen size||Resolution||Pixel density||Pixel size
|Angular pixel density
(px/°; at typ. distance)
|Apple Watch 38mm||Retina display||1.32 in (34 mm)||272×340||326||128||0.0779||56.9||10 in
|Apple Watch 42mm||1.54 in (39 mm)||312×390||326||128||0.0779||56.9||121,680|
|iPhone 4, and 4S and iPod Touch (4th generation)||3.5 in (89 mm)||960×640||326||128||0.0779||56.9||614,400|
|iPhone 5, 5C, 5S and SE and iPod Touch (5th generation, 6th generation)||4 in (100 mm)||1136×640||56.9||727,040|
|iPhone 6, iPhone 6S, iPhone 7 and iPhone 8||Retina HD Display||4.7 in (120 mm)||1334×750||56.9||1,000,500|
|iPhone 6 Plus, iPhone 6S Plus, iPhone 7 Plus and iPhone 8 Plus||5.5 in (140 mm)||1920×1080||401||158||0.0633||70.0||2,073,600|
|iPhone X, iPhone XS||Super Retina HD Display||5.8 in (150 mm)||2436x1125||458||180||0.0555||79.9||2,740,500|
|iPhone XS Max||6.5 in (170 mm)||2688x1242||458||180||0.0555||79.9||3,338,496|
|iPhone XR||Liquid Retina HD Display||6.1 in (155 mm)||1792 x 828||326||128||0.0779||56.9||1,483,776|
|iPad Mini 2, 3, and 4||Retina display||7.9 in (200 mm)||2048×1536||326||128||0.0779||85.4||15 in
|iPad (3rd, 4th generation, Air, Air 2, Pro, 5th generation/2017, and 6th generation/2018)||9.7 in (250 mm)||264||104||0.096||69.1|
|iPad Pro (10.5)||10.5 in (270 mm)||2224×1668||3,709,632|
|iPad Pro (12.9)||12.9 in (330 mm)||2732×2048||69.3||5,595,136|
|MacBook (Retina) 12"||12 in (300 mm)||2304×1440||226||89||0.11||79.0||20 in
|MacBook Pro (3rd generation) 13", MacBook Air (3rd generation/2018) 13"||13.3 in (340 mm)||2560×1600||227||79.2||4,096,000|
|MacBook Pro (3rd generation) 15"||15.4 in (390 mm)||2880×1800||221||87||0.12||77.0||5,184,000|
|iMac with Retina 4K Display 21.5"||Retina 4K Display||21.5 in (550 mm)||4096×2304||219||86||76.3||9,437,184|
|iMac with Retina 5K Display 27", and iMac Pro||Retina 5K Display||27 in (690 mm)||5120×2880||218||76.0||14,745,600|
Higher resolution Retina screens are standard on the 3rd-generation MacBook Pro and new MacBook, released in 2013 and 2015, respectively. The 4th-generation MacBook Pro, released in 2016, retains the same Retina display of the previous generation.
Reviews of Apple devices with Retina displays have generally been positive on technical grounds, with comments describing it as a considerable improvement on earlier screens and praising Apple for driving third-party application support for high-resolution displays more effectively than on Windows. While high-dpi displays such as IBM's T220 and T221 had been sold in the past, they had seen little take-up due to their cost of around $8400.
Reviewing the iPhone 4 in 2010, Joshua Topolsky commented:
"to our eyes, there has never been a more detailed, clear, or viewable screen on any mobile device. Not only are the colors and blacks deep and rich, but you simply cannot see pixels on the screen…webpages that would be line after line of pixelated content when zoomed out on a 3GS are completely readable on the iPhone 4, though the text is beyond microscopic."
Former Microsoft employee Bill Hill, an expert on font rendering, offered similar comments:
That much resolution is stunning. To see it on a mainstream device like the iPad—rather than a $13,000 exotic monitor—is truly amazing, and something I've been waiting more than a decade to see. It will set a bar for future resolution that every other manufacturer of devices and PCs will have to jump.
Writer John Gruber suggested that the arrival of Retina displays on computers would trigger a need to redesign interfaces and designs for the new displays:
The sort of rich, data-dense information design espoused by Edward Tufte can now not only be made on the computer screen but also enjoyed on one. Regarding font choices, you not only need not choose a font optimized for rendering on screen, but should not. Fonts optimized for screen rendering look cheap on the retina MacBook Pro—sometimes downright cheesy—in the same way they do when printed in a glossy magazine.
Raymond Soneira, president of DisplayMate Technologies, has challenged Apple's claim. He says that the physiology of the human retina is such that there must be at least 477 pixels per inch in a pixelated display for the pixels to become imperceptible to the human eye at a distance of 12 inches (305 mm). Astronomer and science blogger Phil Plait notes, however, that, "if you have [better than 20/20] eyesight, then at one foot away the iPhone 4S's pixels are resolved. The picture will look pixelated. If you have average eyesight [20/20 vision], the picture will look just fine... So in my opinion, what Jobs said was fine. Soneira, while technically correct, was being picky." The retinal neuroscientist Bryan Jones offers a similar analysis of more detail and comes to a similar conclusion: "I'd find Apple's claims stand up to what the human eye can perceive."
Apple fan website CultOfMac stated that the resolution the human eye can discern at 12 inches is 900 PPI, concluding "Apple's Retina Displays are only about 33% of the way there." On the topic of 20/20 vision, they said "most research suggests that normal vision is actually much better than 20/20. In fact, people with normal vision usually won't see their eyesight degrade to 20/20 until they are 60 or 70 years of age" (confirmed by vision testing experts Precision Vision). CultOfMac also noted that people do not always view displays at a constant distance, and will sometimes move closer, at which point the display could no longer be classed as Retina.
The first smartphone following the iPhone 4 to ship with a display of a comparable pixel density was the Nokia E6, running Symbian Anna, with a resolution of 640 × 480 at a screen size of 62.5mm. This was an isolated case for the platform however, as all other Symbian^3-based devices had larger displays with lower resolutions. Some older Symbian smartphones, including the Nokia N80 and N90, featured a 2.1 inch display at 259 ppi, which was one of the crispest at the time. The first Android smartphones with the same display - Meizu M9 was launched a few months later in beginning of 2011. And in October of the same year Galaxy Nexus was announced, which had a display with a better resolution. And by 2013 the 300+ ppimark was found on midrange phones such as the Moto G. From 2013–14, many flagship devices such as the Samsung Galaxy S4 and HTC One (M8) had 1080p (FHD) screens around 5-inches for a 400+ PPI which surpassed the Retina density on the iPhone 5. The latest major redesign of the iPhone, the iPhone 6, has a 1334 × 750 resolution on a 4.7-inch screen, while rivals such as the Samsung Galaxy S6 have a QHD display of 2560 × 1440 resolution, close to four times the number of pixels found in the iPhone 6, giving the S6 a 577 PPI that is almost twice that of the iPhone 6's 326 PPI.
The larger iPhone 6 Plus features a "Retina HD Display", which is a 5.5-inch 1080p screen with 401 PPI, which barely meets or lags behind Android phablet rivals such as the OnePlus One and Samsung Galaxy Note 4. Aside from resolution, all generations of iPhone Retina displays receive high ratings for other aspects such as brightness and color accuracy, compared to those of contemporary smartphones, while some Android devices such as the LG G3 have sacrificed screen quality and battery life for high resolution. Ars Technica suggested the "superfluousness of so many flagship phone features—the move from 720p to 1080p to 1440p and beyond...things are all nice to have, but you’d be hard-pressed to argue that any of them are essential". Furthermore, developers can better optimize content for iOS due to Apple's few screen sizes in contrast to Android's wide display format variations.
Many Windows-based Ultrabook models have offered 1080p (FHD) screens standard since 2012 and often QHD or QHD+ as optional upgrade displays. Retina screens are standard on the 3rd-generation MacBook Pro and MacBook, released in 2012 and 2015, respectively.[not in citation given] Apple implemented a Retina display in the third generation of its entry-level laptop line, the MacBook Air, in 2018.
There's only one problem: Steve Jobs said that the human eye, viewing a display from 12 inches away, can't discern individual pixels if the density is over 300 pixels per inch. Except that this "magic" number is wrong. The real number is closer to 900 pixels per inch. Apple's Retina Displays are only about 33% of the way there... But while 20/20 vision might traditionally refer to "standard vision", most research suggests that normal vision is actually much better than 20/20. In fact, people with normal vision usually won't see their eyesight degrade to 20/20 until they are 60 or 70 years of age!... J. Blackwell of the Optical Society of America determined back in 1946 that the resolution of the human eye was actually closer to 0.35 arc minutes. Again, this means that for an iPhone 4S to have a true Retina Display, it would need pixels that were 65% smaller than it currently has... Such an argument is faulty. For one thing, no one sits a uniform average distance away from their devices. When you text on your iPhone, you might hold it at 12 inches, but if you're squinting at it in the middle of the night to answer a phone call, you might hold it 6 inches away. And while you might write an email on your MacBook Pro at 24 inches, you might lean in on the edge of your seat during an exciting movie or game to closer to 18.
"Normal" visual acuity for healthy eyes is one or two lines better than 20/20. In population samples the average acuity does not drop to the 20/20 level until age 60 or 70. Always remember that the 20/20 reference standard does not refer to the average acuity of American eyes, just as the US standard foot is defined independently of the "normal" length of American feet.
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