#Retina displays
To user Philip Schiller's own words from the WWDC2012:
...which means: The pixels of this display are so small that from a normal working distance your retina cannot discern those individual pixels. (watch at youtube)
There is no industry standard for "retina display". The term retina display is relative, as the definition follows the human eyes's perception of a display's sharpness.
When the iPhone 4 was introduced, Steve Jobs made the following definition:
At a distance of 10" to the human eye (or retina), a pixel density of 300PPI is the maximum that an eye can distinguish.
Because this definition is relative, calling a display a retina display depends on two factors:
- pixel density
- distance between the human eye an the display
Both the iPhone 4S and the new iPad have "retina displays" when you apply Steve Job's definition. A mathematical explanation can be found in this answer.
