Steve Jobs announced iPhone 4 at the Worldwide Developers Conference today, calling it the biggest leap since the original iPhone. At 9mm thick, it’s 24% thinner than the iPhone 3GS (but weighs 3 grams more), it has a front-facing camera (VGA resolution) with “FaceTime” video calling (but it’s Wi-Fi only), an LED flash alongside its new 5-megapixel camera’s lens on the back, and separate buttons for volume up, down and mute. It also has a stainless steel rim that functions as the antenna.

Its 3.5-inch display, the same size as current iPhones, has higher resolution (960 x 640 pixels), with four times the pixel count of its predecessor. Jobs is calling it the “retina display.” That’s because, as Jobs put it, “There’s a magic number around 300dpi, if you hold something about 10 to 12 inches away from your eye, it’s the limit of the human retina to distinguish pixels.” The kicker? IPhone 4 has 326dpi resolution.

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