Explaining the difference between a Retina vs. a non-Retina display

-- written by Sebastian Raschka on March 24, 2014
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Recently, someone wanted me to explain the difference between a Retina vs. a non-Retina display. I had to explain it to her via email, and the catch was that the other person was reading/seeing it on a non-Retina monitor.

retina_vs_nonretina_1.png


The term "Retina display" is a marketing concept used by Apple for their high-resolution LCD displays. A display has "Retina" quality, if the human eye can't distinguish between individual pixels anymore - at a typical viewing distance. To achieve such an effect, the displays require a sufficiently high pixel density, which is typically measured in PPI (pixels per inch).
However, this number also varies with the size of the device (and its "typical" viewing distance), for example, a non-Retina iPad Mini (1st gen) has 163 PPI, whereas the Retina version of the iPad Mini (2nd gen) has 326 PPI. For comparisons, the iPhone 5S also has a pixel density of also 326 PPI, but the iPad Air only has 264 PPI (although the resolution is similar to the Retina iPad Mini with 2048x1536 pixels).


Device Pixel density in PPI 
(in pixels per inch)
Resolution
(in pixels x pixels)
iPhone 5S Retina 326 1136x640
iPad Mini non-Retina (1st gen) 163 1024x768
iPad Mini Retina (2st gen) 326 2048x1536
iPad Air Retina 264 2048x1536

(Source: Wikipedia)

To keep a long story short and to give you another visual example: Below you find set of screenshots and screen photos that I took from the home screens of my iPhone 5S (Retina) and iPad Mini (non-Retina), respectively. Of course, the ideal case would have been, for example, two iPad Minis - one with a Retina and one without Retina diplay. Unfortunately, those were the only two devices available at this point in time, but I will update the post if I get my hands on some more iOS handhelds.

retina_vs_nonretina_2.png (Screenshots taken on the devices via 'Lockscreen + Homescreen' buttons)



retina_vs_nonretina_camera_1.png (Screen photos taken with a camera)


And those are the original screenshots I took from both devices without zooming in on the 'Contacts' icon:


retina_nonretina_orig_iphone.png (iPhone 5S, Retina)


retina_nonretina_orig_ipad.png (iPad Mini 1st gen, non-Retina)