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The Apple In Your Eye

June 14, 2010

Much has been said about the claims that Steve Jobs made regarding the iPhone 4's new Retina Display. It is good, but is it really all that he is making it out to be? The iPhone 4 display is a 3.5" screen (measured diagonally) with a resolution of 960x640, which comes out to four times the number of pixels of the previous iPhone. The jump in clarity is roughly akin to when you saw your first HDTV. The most astonishing claim made about the display is that it is so detailed, your eye cannot physically make out the pixels at all. If true, your eye would have trouble discerning between a picture of a flower and the flower itself. Jobs claims that at 1 foot away, the 326 pixels-per-inch resolution is actually more than your eye can see. However, your eye doesn't have "pixels" or a "ppi" rating, so it is hard to verify, by the common man. That's where the complicated math comes in. The ability of your eye to distinguish pixels, or any other object, is measured in angles. Your eyes can only make out so many object across your entire field of vision. That is why the further away something is, the larger it has to be to make out. So how well your eye can make out pixels on the iPhone is a product of the angles your eye can discern, distance from the screen, etc.

Chances are, if it has been a while since your last algebra class, you may be getting a headache right now. Luckily, Vern Seward at The Mac Observer did most of the math for us. An eye with 20/20 vision can discern images at the angle of 1 arcminute. That means at 1 foot from the eye, you can see objects 0.0035 inches in size. Now if you compare that to Apple's screen, its pixels are only 0.0031 inches in size. That means that someone with good eyesight, holding it a foot away, will not be able to make out pixels. So is Steve right? The answer is yes and no. The science obviously backs his claims, but there are some things to consider. 20/20 is considered "good' vision, but it's not perfect. People with perfect vision can see objects at angles of 0.6 arcminutes. That means that individuals with perfect vision might be able to discern some pixel edges. However, pay attention to how close you hold your iPhone some time. If you keep the phone about as far away as you do your keyboard, that is closer to 18-24 inches. At that distance, even someone with perfect eyesight can't make out the pixels. So does the screen on the iPhone 4 look perfect to the naked eye? We'll just have to see for ourselves on June 24th.

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