[9] Apple uses various marketing terms to differentiate between its LCD and OLED displays having various resolutions, contrast levels, color reproduction, or refresh rates.
[11] Apple's Retina displays do not have a fixed minimum pixel density, but vary depending on and at what distance the user would typically be viewing the screen.
When introducing the iPhone 4, Steve Jobs said the density of pixels needed for a Retina display is about 300 PPI (120 dot/cm) for a device held 10 to 12 inches (25 to 30 cm) from the eye.
For example, holding a phone 11 in (28 cm) 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.
[13] 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).
[19] 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.
[32] 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.
"[33] Former Microsoft employee Bill Hill, an expert on font rendering, offered similar comments: That much resolution is stunning.
[36]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.
By 2013 the 300+ ppimark was found on midrange phones such as the Moto G.[37] 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.
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".
[37] Furthermore, developers can better optimize content for iOS due to Apple's few screen sizes in contrast to Android's wide display format variations.
[38] Many Windows-based Ultrabook models have offered 1080p (FHD) screens standard since 2012 and often QHD or QHD+ as optional upgrade displays.