A type of high resolution display by Apple with a pixel density of around 264-326 points per inch (PPI).
Retina Displays (marketed by Apple with a stylized lowercase 'D' as Retina display) is a brand name used by Apple for screens that have a pixel density of around 300 PPI.
The term is used for several Apple products, including the iPhone, iPod Touch, iPad, MacBook Pro, iPad Mini, and iPad Air.
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(points per inch) for smaller displays and lower PPI for larger displays:
- 326 PPI for the smallest devices (iPhone, iPod Touch, and iPad Mini (2nd generation)),
- 264 PPI for mid-sized devices (iPad (3rd & 4th generations), iPad Air), and 220 PPI for larger devices (MacBook Pro).
Many other manufacturers' displays have similar or higher pixel 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.
On November 27, 2012 the US Patent and Trademark office approved Apple's application and "Retina" is now a registered trademark for computer equipment.
Source/further info: http://en.wikipedia.org/w/index.php?title=Retina_Display&oldid=619438414