Each week Ross Rubin contributes Switched On, a column about consumer technology.
In that human-behavior lab known as the New York City subway, a vacationing family recently sought to get in a group self-portrait on their last day in the Big Apple. But the rocking train kept thwarting the capture of their jostled bodies. To frame the picture, they tried trading the quality of their smartphone's rear camera for the one above the phone's display so they could better preview t
