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and 30 times harder than plastic," theoretically allowing it to be more scratch resistant and durable than the previous models. The iPhone 4 switches the placement of the microphone and speaker on the base on the unit — the speaker is now on the left. The display on the iPhone 4 features an LED backlit LCD capacitive touchscreen with a pixel density of 326 pixels per inch (ppi) on a 3.5 inches (8.9 cm) (960-by-640) display, each pixel is 78 micrometers in width. The display has a contrast ratio of 800:1. The screen is marketed by Apple as the "Retina Display," based on the assertion that a display of approximately 300 ppi at a distance of 12 inches (305 mm) from one's eye is the maximum amount of detail that the human retina can process. With the iPhone expected to be used at a distance of about 12 inches from the eyes, a higher resolution would allegedly have no effect on the image's apparent quality as the maximum potential of the human eye has already been met. The display has been the subject of some controversial criticism; focused primarily on Apple's claims that the displays resolution exceeds the maximum amount of detail that the human retina can process. Raymond Soneira, president of DisplayMate Technologies, reported in an interview with Wired Magazine saying
Hardware
Display
that the claims by Jobs are something of an exaggeration: "It is reasonably close to being a perfect display, but Steve pushed it a little too far". Soneira continued to state that the resolution of the retina is higher than claimed by Apple, working out to 477 ppi at 12 inches (305 mm) from the eyes. However, Phil Plait, author of Bad Astronomy, whose career includes a collaboration with NASA regarding the camera on the Hubble Space Telescope, responded to the criticism by stating that "if you have [better than 20/20] eyesight, then at one foot away the iPhone 4’s pixels are resolved. The picture will look pixellated. If you have average eyesight, the picture will look just fine."