If you are not an owner of the latest technology from Apple, you may have heard of “retina display” and wondered what does the term mean. In the iPhone 4 page in Wikipedia, there is a good definition of the term: (the bold highlighting was added by me):
The display of the iPhone 4 is manufactured by LG under an exclusive contract with Apple. It features an LED backlit TFT LCD capacitive touchscreen with a pixel density of 326 pixels per inch (ppi) on a 3.5 in (8.9 cm) (diagonally measured), 960×640 display. Each pixel is 78 micrometres in width. The display has a contrast ratio of 800:1. The screen is marketed by Apple as the “Retina Display”, based on the assertion that a display of approximately 300 ppi at a distance of 12 inches (305 mm) from one’s eye, or 57 arcseconds per pixel is the maximum amount of detail that the human retina can perceive. With the iPhone expected to be used at a distance of about 12 inches from the eyes, a higher resolution would allegedly have no effect on the image’s apparent quality as the maximum potential of the human eye has already been met.
Interesting, the claim was disputed by
Raymond Soneira, president of DisplayMate Technologies (who) said in an interview with Wired magazine, that the claims by Jobs are something of an exaggeration: “It is reasonably close to being a perfect display, but Steve pushed it a little too far.” Soneira stated that the resolution of the human retina is higher than claimed by Apple, working out to 477 ppi at 12 inches (305 mm) from the eyes, or 36 arcseconds per pixel.
But as you can see, for all intents and purposes, the iPhone 4 (and likely later Apple technology) meets this standard:
However, Phil Plait, author of Bad Astronomy, whose career includes a collaboration with NASA regarding the camera on the Hubble Space Telescope, responded to the criticism by stating that “if you have [better than 20/20] eyesight, then at one foot away the iPhone 4’s pixels are resolved. The picture will look pixellated. If you have average eyesight, the picture will look just fine.”
In a nutshell, if a display is such that you cannot see the pixels, then it is a retina display.
I expect that retina display will come to bigger and bigger screens as the technology advances. First the iPhone, then the iPad and other tablets, to…well as big as displays can get.