Some Retina iPad minis are demonstrating image retention issues, as noted by Instapaper creator Marco Arment, who originally developed a grid test to detect the problem in Retina MacBook Pros. Image retention was first cited as a potential issue last week, when a rumor suggested that burn-in on Sharp's IGZO panels was causing production delays with the Retina mini's display, leading to significant supply constraints that have resulted in a quiet release for the tablet. While it is unclear how many Retina iPad minis are affected by the issue, several mini
