#Retina displays

To user [Philip Schiller](https://twitter.com/#!/pschiller)'s own words from the [WWDC2012](https://developer.apple.com/wwdc/):

> ...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](http://www.youtube.com/watch?v=EHcVjajO4LM&feature=youtu.be))

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:

1. **pixel density**
2. **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](http://apple.stackexchange.com/a/44222/13414).

 ![enter image description here][2] ![enter image description here][1]

  [2]: https://i.sstatic.net/1KWn7.png

  [1]: https://i.sstatic.net/zWfta.jpg