title: What is down sampling and up sampling in iPhone resolution?
body: <p>I am following this link for iPhone device resolution guide. Since long while i am facing couple of words like DownSampling, UpSampling and Display Zoom on this <a href="http://www.paintcodeapp.com/news/ultimate-guide-to-iphone-resolutions" rel="nofollow">PaintCode</a>. But i am confused with Physical Pixels and Rendered Pixels. </p>
  
  <p>Does not getting which resolution to use when adding images ?</p>
  
  <p>Please explain this situation , if any of know it in detail.
  Thanks</p>