retina display

{{See also|Fovea centralis#Angular size of foveal cones}}

When introducing the iPhone 4, Steve Jobs said the density of pixels needed for a Retina display is about {{convert|300|dpi|dpcm|disp=x| PPI (| dot/cm)|abbr=values}} for a device held {{convert|10|to|12|in|cm}} from the eye.{{cite web|url=http://m.npr.org/story/127530049|title=NPR Live Blog of iPhone 4 Introduction|publisher=NPR|date=June 7, 2010|access-date=June 4, 2014}} This definition includes the distance from the screen to the observer (the viewing distance), because moving the eye closer to the display makes it easier to see detail up close, and moving away makes it harder. One metric that takes into account both the pixel density of a screen and the viewing distance is angular pixel density, typically expressed in units of pixels per degree (PPD). For pixels centered in the field of vision spanning a small visual angle, the angular pixel density can be approximated as:{{cite journal |last1=Mantiuk |first1=Rafał K. |last2=Denes |first2=Gyorgy |last3=Chapiro |first3=Alexandre |last4=Kaplanyan |first4=Anton |last5=Rufo |first5=Gizem |last6=Bachy |first6=Romain |last7=Lian |first7=Trisha |last8=Patney |first8=Anjul |title=FovVideoVDP: a visible difference predictor for wide field-of-view video |journal=ACM Transactions on Graphics |date=31 August 2021 |volume=40 |issue=4 |pages=1–19 |doi=10.1145/3450626.3459831}}

:$\backslash frac\{\backslash pi\}\{360\; \backslash arctan\; \backslash left\; (\backslash frac\{0.5\}\{d\; r\}\backslash right)\}$

where $d$ is the distance between the screen and observer (e.g. in meters), and $r$ is the absolute pixel density of the screen in pixels per unit length (e.g. in pixels per meter).

Based on Jobs' statement, the threshold for a Retina display is an angular pixel density of 52–63 PPD. For example, holding a phone {{convert|11|in|cm|abbr=on}} away, the value of 58 PPD means that a tall skinny triangle emanating from the eye 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 58 pixels.

The essence of Retina display is to eliminate the appearance of graininess on a screen, for example when displaying complex languages (for example Arabic, Hebrew and CJKV) on a screen.

Many authors have challenged Apple's claim. For example, Raymond Soneira, president of DisplayMate Technologies, said 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 {{convert|12|inch|mm|0}}, corresponding to 0.6 arcminutes per pixel or 100 PPD.{{cite web|url=https://www.pcmag.com/article2/0,2817,2364871,00.asp|title=Analyst challenges Apple's iPhone 4S 'Retina Display' claims|date=June 9, 2010|access-date=June 10, 2010}} John Brownlee, in an article at Apple fan website CultOfMac, stated that the threshold to discern individual pixels is between 0.3 and 0.4 arc minutes (150 - 200 PPD).{{cite web|last=Brownlee|first=John|date=June 15, 2012|title=Why Retina Isn't Enough|url=http://www.cultofmac.com/173702/why-retina-isnt-enough-feature|access-date=June 15, 2012|website=CultOfMac}} Others have defended Apple. Astronomer and science blogger Phil Plait stated that a resolution of 0.6 arcminutes corresponds to "perfect eyesight" but that "a better number for a typical person is more like 1 arcmin resolution, not 0.6", corresponding to 20/20 vision or 60 PPD. Plait argued that what Jobs said was fine as the iPhone 4S's resolution is better than 1 arcmin.{{cite web|url=http://blogs.discovermagazine.com/badastronomy/2010/06/10/resolving-the-iphone-resolution|title=Resolving the iPhone resolution|date=June 21, 2010|access-date=June 21, 2010|archive-date=October 5, 2012|archive-url=https://web.archive.org/web/20121005101858/http://blogs.discovermagazine.com/badastronomy/2010/06/10/resolving-the-iphone-resolution/|url-status=dead}}{{cite news |last1=Plait |first1=Phil |title=Resolving the iPhone resolution |url=https://slate.com/technology/2010/06/resolving-the-iphone-resolution.html |journal=Slate |date=10 June 2010 |publisher=slate.com |access-date=9 October 2021|quote="...Soneira used the 0.6 arcmin resolution of the eye, but that’s for perfect eyesight. Most people don’t have perfect eyesight... A better number for a typical person is more like 1 arcmin resolution, not 0.6"}} The retinal neuroscientist Bryan Jones cites a paper calculating 0.78 arcminutes/cycle of *retinal* resolution (corresponding to 77 PPD), and states the optics of the system may degrade image quality somewhat, thus giving the commonly accepted resolution of 1 arcminute.{{cite web|url=http://prometheus.med.utah.edu/~bwjones/2010/06/apple-retina-display|title=Apple Retina Display|date=July 26, 2012|access-date=July 26, 2012}} Soneira has replied that "If you allow poor vision to enter into the specs, then any display becomes a retina display. That turns it into a meaningless concept that will be exploited by everyone."{{cite news |last1=Chen |first1=Brian X. |title=Display Expert: iPhone 4 Resolution 'Significantly Lower' Than Retina |url=https://www.wired.com/2010/06/iphone-4-retina-2/ |work=Wired |date=14 June 2010}} A 2024 study found that the eye had resolution limits of 94 PPD for foveal achromatic vision, 89 PPD for red-green patterns, and 53 PPD for yellow-violet patterns.{{cite arXiv |last1=Ashraf|first1=Maliha|last2=Chapiro|first2=Alexandre|last3=Mantiuk|first3=Rafał K. |date=8 October 2024|title=Resolution limit of the eye: how many pixels can we see?|arxiv=2410.06068v1 |class=cs.HC}}

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 only exceptions to this have been the iPhone 6 Plus, 6S Plus, 7 Plus, and 8 Plus, which render their images at triple the number of pixels in each direction, before down-sampling to 1080p resolution.

The displays are manufactured worldwide by different suppliers. Currently, the iPad's display comes from Samsung,{{cite web|url=https://www.wired.co.uk/news/archive/2012-04/04/why-samsung-makes-retina-displays|title=Why Samsung makes Retina Displays – but not for its own tablets|publisher=Wired magazine|date=April 4, 2012|access-date=June 4, 2013}} while the MacBook Pro and iPod Touch displays are made by LG Display{{cite web|url=http://www.ifixit.com/Teardown/MacBook-Pro-Retina-Display-Teardown/9493/1|title=iFixit Teardown|date=19 June 2012 |publisher=iFixit|access-date=July 9, 2012}} and Japan Display Inc.{{cite news|url=https://www.reuters.com/article/us-japan-display-listing-idUSBREA2I00W20140319?type=companyNews|title=News related to IPO of Japan Display Inc.|newspaper=Reuters |date=March 19, 2014|access-date=March 20, 2014}} 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 Retina, Retina HD, Liquid Retina, Liquid Retina XDR, Super Retina HD, Super Retina XDR, Ultra Retina XDR or Retina 4K, 5K or 6K displays:

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.{{cite web|last1=Castle|first1=Alex|title=How to make the Windows desktop look good on high-DPI displays|url=http://www.pcworld.com/article/2098586/how-to-make-the-windows-desktop-look-good-on-high-dpi-displays.html|website=PC World|access-date=9 July 2015}}{{cite web|last1=Cunningham|first1=Andrew|title=Using the Retina MacBook as a Windows PC|url=https://arstechnica.com/apple/2015/04/using-the-retina-macbook-as-a-windows-pc/|website=Ars Technica|date=13 April 2015 |access-date=9 July 2015}}{{cite web|last1=Hutchinson|first1=Lee|title=The Retina iMac and its 5K display... as a gaming machine? [Updated]|url=https://arstechnica.com/apple/2014/10/the-retina-imac-and-its-5k-display-as-a-gaming-machine/2/|website=Ars Technica|date=28 October 2014 |access-date=9 July 2015}} 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.{{cite web|last1=Novakovic|first1=Nebojsa|title=IBM T221 - the world's finest monitor?|url=http://www.theinquirer.net/inquirer/news/1012426/ibm-t221-world-finest-monitor|archive-url=https://web.archive.org/web/20090914114750/http://www.theinquirer.net/inquirer/news/1012426/ibm-t221-world-finest-monitor|url-status=dead|archive-date=September 14, 2009|website=The Inquirer|access-date=30 August 2015}}

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."{{cite web|last1=Topolsky|first1=Joshua|title=iPhone 4 review|url=https://www.engadget.com/2010/06/22/iphone-4-review/|website=Engadget|access-date=9 July 2015}}

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.{{cite web|last1=Hill |first1=Bill |title=The Future of Reading (quoted) |url=http://billhillsblog.blogspot.com/2012/03/3rd-generation-ipad-entering-high.html |website=Blog (archived) |url-status=dead |archive-url=https://web.archive.org/web/20120312043221/http://billhillsblog.blogspot.com/2012/03/3rd-generation-ipad-entering-high.html |archive-date=March 12, 2012 }}{{cite web|last1=Atwood|first1=Jeff|title=Welcome to the Post PC Era|url=http://blog.codinghorror.com/welcome-to-the-post-pc-era/|website=Coding Horror|date=19 March 2012 |access-date=9 July 2015}}

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.{{cite web|last1=Gruber|first1=John|title=Pixel Perfect|url=http://daringfireball.net/2012/08/pixel_perfect|website=Daring Fireball|access-date=18 September 2015}}

Three years prior the release of the iPhone 4, Eten released the glofiish X800 (November 2007) featuring a 286 ppi display (2.8 inch VGA){{cite web|title=Eten glofiish X800 Full phone specifications|url=https://www.gsmarena.com/eten_glofiish_x800-1926.php|access-date=14 April 2025}} making it one of the first high density display smartphone.

Asus announced the P750 in October 2007 (and released in April 2008).{{cite web|title=Asus P750 Full phone specifications|url=https://www.gsmarena.com/asus_p750-2170.php|access-date=14 April 2025}} It features a 2.6 inch screen with 640 x 480 resolution at 307 ppi, but the software limited it to QVGA (320 x 240, 154 ppi) via pixel quadrupling. Users could unlock the full potential of the screen via software modifications making it one of the earliest high density display smartphone{{cite web|title=Asus P750 review: Significant other|url=https://www.gsmarena.com/asus_p750_review-review-260p5.php|access-date=14 April 2025}} making it one of the first smartphones with a display density over 300 ppi. The Windows Mobile operating system supports DPI independent rendering, thus all applications immediately and seamlessly benefited from the increased screen density making text clearer and sharper.

Two years prior to the release of device with a high density screen from Apple, HTC released the HTC Touch Diamond with a 286 ppi screen. In October 2008 the Sony Ericsson Xperia X1 was one of the first smartphones which offered higher resolution than the VGA screens seen before. It has a 800 x 480 screen at 311 ppi.

One of 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-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 sharpest at the time. The first Android smartphones with the same display - Meizu M9 was launched a few months later in beginning of 2011. In October of the same year Galaxy Nexus was announced, which had a display with a better resolution. By 2013 the 300+ ppimark was found on midrange phones such as the Moto G.{{cite web|last=Cunningham |first=Andrew |url=http://arstechnica.co.uk/gadgets/2015/08/review-new-180-moto-g-is-a-stylish-upgrade-worthy-of-the-original/2/ |title=Review: New £180 Moto G is a stylish upgrade worthy of the original | Ars Technica UK |publisher=Arstechnica.co.uk |date=2015-08-10 |access-date=2016-01-15}} From 2013 to 2014, 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 second 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.{{cite web|url=http://www.techradar.com/us/news/phone-and-communications/mobile-phones/samsung-galaxy-s6-vs-iphone-6-1286508|title=Samsung Galaxy S6 vs iPhone 6|date=6 June 2023 }} The Sony Xperia Z5 Premium launched in late 2015 had 806 PPI. The larger iPhone 6 Plus features a "Retina HD display", which is a 5.5-inch 1080p screen with 401 PPI.

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 has 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.{{citation needed|date=November 2018}}

• Resolution independence
• Pixel density
• HiDPI
• Pixelplus

{{Reflist}}

Category:Apple Inc. displays

Category:Computer display standards

Category:IPhone

Category:IPad

Category:LCD brand names