The scale factor is tripled for devices with even higher pixel densities, such as the iPhone 6 Plus and iPhone X.
In simpler words, it is one logical pixel = four physical pixels. The Retina display debuted in 2010 with the iPhone 4 and the iPad 3, where each screen pixel of the iPhone 3GS and iPad 2 was replaced by four smaller pixels, and the user interface scaled up to fill in the extra pixels. The Canadian application cited a 2010 application in Jamaica. The applications were approved in 20 respectively. Apple has registered the term 'Retina' as a trademark with regard to computers and mobile devices with the United States Patent and Trademark Office and Canadian Intellectual Property Office. Retina Display is a brand name used by Apple for its series of IPS LCD and OLED displays that have a higher pixel density than traditional Apple displays. The pixels are visible at normal viewing distance. Part of a non-Retina display on an iPhone 3GS.
