I was thinking about getting a headphone jack button thingie; you plug it into the jack, and set it to do one of a set of available actions. I thought I’d try the camera to see whether I could reach to use it as a photo shutter, taking pictures one-handed. It was too awkward, but something near the volume buttons would be perfect. I opened the camera app to see whether I could set custom buttons. Lo and behold, there is such a setting…and the default for the volume buttons is “take picture”. I’ve had this phone since the end of September, and I’ve looked in the camera settings many times. Obviously not closely enough because I could have been using that feature all along; it’s on by default. Duh!