The latest gadget that has taken the world by storm, the Apple iPhone 4 has plenty of features to show off. One of the novel, never-before features is its Retina Display. So what is retina display?

The 3.5-inch screen of the iPhone 4 has a resolution of 960 x 640 pixels. This resolution is the highest that any smartphone has offered till date. It is 4 times the resolution offered by the previous iPhones as well [iPhone 3GS resolution - 480 x 360 pixels]. This means super clarity.

According to Apple, the human eye will not be able to differentiate between pixels, when the pixel density exceeds 300 pixels per inch (ppi). The pixel density of the iPhone 4 retina display is 326 ppi, which is above the limit. Thus, even when pictures and text are zoomed in, the clarity will still be retained. This property of the screen, has led to calling it the Retina Display. The iPhone 3GS has a pixel density of just 163 ppi. The picture below from MobileCrunch compares a shot between the iPhone 4 (left) and the iPhone 3GS (right). Click on it for the original image and you'll see that even on zooming the image, the icons on the iPhone 4 screen remain clear.

There have been reports contradicting as well as supporting Apple's claims. Plenty of math has gone into justifying whether the iPhone 4 screen can or cannot be called Retina Display. However, seeing is believing. For the everyday user, great clarity and great user experience are what matter. Robert Scoble, a Flickr user, has taken a picture with a pro DSLR camera of the iPhone 4 showing a page of The New York Times. The picture speaks of the clarity of the iPhone 4 Retina Display.

The iPhone 4 screen has a contrast ratio of 800:1. This is said to be 4 times the contrast ratio of the iPhone 3GS screen. Plus, the former is said to offer better brightness levels than the latter too. The iPhone 4 display also uses LED backlight and IPS or In-Plane Switching technology. This technology helps in offering better viewing angles and better colour reproduction. With all these features, the Apple iPhone 4 is definitely the biggest leap since the first iPhone.

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