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Twenty-eight years ago, a monochrome icon on the Mac was 16×16 pixels. It only took 32 bits of memory. Compare to the 512×512 pixels of each iOS’ icon. It takes four times the total video memory of the original Mac to represent a single icon in iOS at full size. Of course, iOS icons are not shown on screen at that size. They are much smaller. Eventually, however, you can be sure that there will be displays that would require that insane pixel density.
What is remarkable is that the absolute size of the icons remains more or less the same. It’s an amazing increase in the density of information required to represent the exact same object with the exact same meaning. Eye candy is expensive.
Another comparison: the new iPad 2012 has a 2048×1536 screen, with 9.7-inch physical size. That’s four times as many pixels long by 4.5 times as many pixels tall as the original Macintosh, which had a 9-inch screen.
If anyone had told me this when I tried my first Mac, back in the ’80s, I would have never believed it.