How Retina is your display?

TUAW editor Richard Gaywood did the math to determine what qualifies as a Retina Display — one with a pixel density so high, that it equals or exceeds that of your eyes.

Bottom line...

• Retina-ness depends a lot on how far your eyes are from the display.
  
  
• For phones, 315 ppi (or higher) qualifies as a Retina Display.
  
  
• For tablets, 215 ppi is enough.
  
  
• For laptops and desktops, the requirement is lower. How much lower, depends on your viewing distance.
  
  
• A 50-inch or smaller 1080p TV will be Retina (or near-Retina) at viewing distances of 6 feet or farther, provided that the content is 1080p resolution (e.g., Blu-Ray).
  
  
• A display doesn't have to be fully Retina to look good. A pixel density that's 75% Retina will still look very sharp.
  
  
• Moving video creates the illusion of even higher resolution, since the pixels are constantly in motion.