The Seven Inch iPad
Rumour has it that Apple is going to release a 7" iPad towards the end of the year. My first thought on reading this was an automatic "Apple would never fragment the platform to a third resolution so quickly". Then I got thinking that perhaps they wouldn't have to. What if they kept the same resolution of the iPad but increased the DPI?
There are some limits, though. Currently the iPad has a slightly lower DPI than the original iPhone did (132dpi compared to 163dpi). This means that the icons, text and controls all appear slightly bigger on the iPad. The problem is if it goes too far the other way - if the DPI gets too high - then the icons, text and controls will become too small to be usable.
But we do know that the DPI on the original iPhone is perfectly acceptable. That works just fine. So, what would happen if Apple made an iPad with the same 1024x768 resolution as the current model but which had the same 163dpi as the original iPhone? Would that equate to a 7" display?
If the screen is going to be 1024 pixel tall at 163dpi, then the height of the screen has to be 6.28" (1024 ÷ 163 = 6.28). Similarly, the width of the screen will be 4.7" (768 ÷ 163 = 4.71).
Now we have the width and height, we need the diagonal distance from one corner to the other. Pythagoras, take it away...
Diagonal distance = √ 6.282 + 4.712
= √ 39.43 + 22.18
= √ 61.61
= 7.84 inches
There you have it. If Apple releases an iPad with exactly the same resolution as the existing model (for compatibility) but with the original iPhone's pixel density (for usability), we would get a 7.84" screen.