Noting that Apple has not responded to numerous complaints in its own support forums regarding iPhone 4 proximity sensor problems, iLounge reader Trent Phillips has conducted tests to determine differences between the sensor behaviors of multiple iPhone models, and concluded that an iOS software update is capable of resolving the problems. In an e-mail to iLounge, Phillips says that the iPhones are all capable of deactivating their screens when objects are detected at a two-inch distance from the sensor, but the iPhone 4 behaves differently from its predecessors, making decisions that lead to accidental screen reactivations under certain conditions.
Earlier iPhones, Phillips notes, switch off their screens at the two-inch distance regardless of the color and past motion of the approaching object. By comparison, the iPhone 4 appears to be less sensitive to dark objects than light ones, and also changes its deactivation distance dynamically after the initial contact. Consequently, the iPhone 4’s screen deactivates only from a shorter distance—say, one inch rather than two inches—if the object it initially reacted to was at the shorter distance. Testing with black and white pieces of paper suggested that the “black piece of paper greatly reduced the detection range of the proximity sensor,” which “could also explain why some people see different effects,” says Phillips, based on skin tone, makeup, light levels, and other factors. His belief is that the iPhone 4’s sensor retains the two-inch range of prior iPhones, but has been miscalibrated on the software side, perhaps in an effort to improve battery life. While it’s still unclear as to whether changes in the iPhone 4’s glass material and/or proximity sensor hardware could also be responsible for the issues, Phillips believes from his testing that a software update could fix the problem, and “all may be well again.”