In past experiments, researchers determined that rods in the eye could pick up a minimum of two to seven photons, but they weren’t quite sure because they couldn’t control the exact number of photons in a flash of light. But now researchers have greater control. In this experiment, volunteers were put in a completely dark room. Researchers flashed exactly 30 photons at their eyes, assuming that only about ten percent of them would reach the rod cells. The volunteers had to guess whether the flash came from the right or the left, even if they didn’t think they could see the light. When flashed with only 30 photons, participants responded correctly more often than not, which led the researchers to conclude that the eye could see a minimum of three photons.