Your smartphone can help you spy around corners from afar

Seeing what’s happening on the other side of a corner isn’t as impossible as it sounds.

Scientists have been working on the problem for years, using lasers to bounce light off unseen objects and detect what’s going beyond their line of sight. Now, researchers from MIT’s CSAIL have gone one step further: they’re using footage from an ordinary smartphone to “see” around corners by spotting subtle changes in light and shadow. The premise of the work is simple: all objects reflect light, and, by closely studying the floor near a corner, you can see if something is moving on the other side based on changing shadows. These fluctuations are invisible to the human eye, but researchers were able to spot them by tweaking the footage from ordinary commercial cameras, and even an iPhone 5s. The method has a number of serious limitations, though. For starters, you can’t make out any detail about the unseen object. You can identify how fast it’s moving, and get some idea of its position, but you can’t make out edges or shape or texture. And, unlike the laser method of seeing around corners, the unseen person or object has to be moving in a brightly lit space in order to be detected. As a last limitation, the source footage also has to be stable, although the researchers are working on how to use moving footage.                                                                     https://www.theverge.com/2017/10/9/16447510/see-round-corners-smartphone-mit-csail-research