Retina Display

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Not to be confused with Virtual retinal display.

Retina Display (marketed by Apple with a stylized lowercase 'd' as Retina display) is a brand name used by Apple for liquid crystal displays that have a pixel density high enough that the human eye is unable to discern individual pixels at a typical viewing distance. The term is used for several Apple products, including the iPhone, iPod Touch, iPad, MacBook Pro, iPad Mini, and iPad Air.[1] Because the typical viewing distance is different, depending on each device's use, the pixels per inch claimed to be of Retina quality can differ, depending on the size of the display, with higher PPI for smaller displays and lower PPI for larger displays: 326 PPI for the smallest devices (iPhone, iPod Touch, and iPad Mini with Retina display), 264 PPI for mid-sized devices (iPad third generation and onwards, including iPad Air), and 220 PPI for larger devices (MacBook Pro). While not currently common, many other manufacturers displays have similar PPI density. 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. 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.[2][3] On November 27, 2012 the US Patent and Trademark office approved Apple's application and "Retina" is now a registered trademark for computer equipment.

Retina Display models

The displays are manufactured by different suppliers in the world. Currently, the iPad's display comes from Samsung,[4] while the Macbook Pro, iPhone, and iPod Touch displays are made by LG and Samsung.[5]

Apple markets the following devices as having Retina Displays:

Model[6][7][8][9] PPI (pixels per inch) ppcm (pixels per cm) Resolution Total Pixels Typical viewing distance (in/cm) Pixels per degree (PPD)
iPhone 4/4S and iPod Touch (4th generation) 326 128 960x640 614,400 10 inches (25 cm) 57
iPhone 5/5C/5S and iPod Touch (5th generation) 1136x640 727,040
iPad (3rd/4th generation/iPad Air) 264 105 2048x1536 3,145,728 15 inches (38 cm) 69
iPad Mini (2nd generation) 326 128 2048x1536 3,145,728 15 inches (38 cm) 85
Macbook Pro (3rd generation) 15" 220 87 2880x1800 aka 2K resolution 5,184,000 20 inches (51 cm) 77
Macbook Pro (3rd generation) 13" 227 89 2560x1600 aka 2K resolution 4,096,000 20 inches (51 cm) 79

Technical definition

When introducing the iPhone 4, Steve Jobs said the magic number for a Retina Display is about 300 PPI for a device held 10 to 12 inches from the eye.[10] 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' magic number of 300, the threshold for a Retina Display starts at a PPD value of 53. 53 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 53 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. 1024x800 pixels) or relative pixel density (e.g. 72 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 multiplying the distance to the screen times the resolution of the screen in pixels per unit length times twice the Tan of π divided by 360 (equal to half a degree in radians). Remember to use units, whether imperial or metric, consistently in applying this formula. If the distance to the screen is measured in inches, then the resolution of the screen must be in PPI. If the distance to the screen is measured in centimetres, the resolution of the screen must be in PPC. Two times the Tan of π divided by 360 can also be approximated with π divided by 180 (= 0.01745).

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, combined with the size-doubling of the user interface, creates a sharper interface at the same physical dimensions.

Criticism

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 resolve (become imperceptible to the human eye) at a distance of 12 inches (305 mm).[11] The 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."[12] Shortly after Soneira's challenge, the Boys of Tech podcast published their own analysis[13] and concluded that Soneira's claim was invalid and that Jobs' claim was correct. This was primarily because Soneira misinterpreted the manner in which the acuity of the human eye can be tested. 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."[14]

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".[15] 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"[15] (confirmed by vision testing experts Precision Vision).[16] 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.[15]

See also

References

  1. ↑ "Apple - Learn about the Retina display". Retrieved June 21, 2010. 
  2. ↑ United States Patent and Trademark Office. "Latest Status Info - Serial Number 85056807". Trademark Applications and Registrations Retrieval. Retrieved June 19, 2012.  Claims priority filing date with respect to prior application in Jamaica.
  3. ↑ Canadian Intellectual Property Office. "Canadian Trade-Mark Data - Application Number 1483982". Canadian Trade-marks Database. Retrieved June 19, 2012.  Also cites prior application in Jamaica.
  4. ↑ "Why Samsung makes Retina Displays -- but not for its own tablets". Wired. "If you haven't yet laid eyes on the new iPad's screen, you must. "Sharp" doesn't begin to describe Apple's upgrade in display quality. But here's the kicker: Samsung, a company firmly aligned with Android and one of Apple's largest competitors in the mobile space, is manufacturing the new iPad's flagship feature." 
  5. ↑ "iFixit Teardown". Retrieved July 9, 2012. 
  6. ↑ "Apple - iPod Touch - Technical Specifications". 
  7. ↑ "Apple - iPhone - Technical Specifications". 
  8. ↑ "Apple - iPad - Technical Specifications". 
  9. ↑ "Apple - MacBook Pro - Technical Specifications". 
  10. ↑ NPR Live Blog of iPhone 4 Introduction
  11. ↑ "Analyst challenges Apple's iPhone 4S 'Retina Display' claims". Retrieved June 10, 2010. 
  12. ↑ "Resolving the iPhone resolution". Retrieved June 21, 2010. 
  13. ↑ "iPhone 4 Retina Display vs the human eye". Retrieved April 30, 2013. 
  14. ↑ "Apple Retina Display". Retrieved July 25, 2012. 
  15. ↑ 15.0 15.1 15.2 Brownlee, John (June 15, 2012). "Why Retina Isn’t Enough". CultOfMac. "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." 
  16. ↑ "Visual Acuity". Precision Vision. "“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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