Plants protect themselves from too much sunlight by turning extra light energy into heat. This process, called nonphotochemical quenching (NPQ), helps prevent damage to their photosynthetic machinery. Scientists are still figuring out exactly how this heat dissipation works. One new method, qPd, measures how much light energy is used for protection versus damaging the plant. Researchers tested this method on a lycophyte plant called Selaginella martensii grown in different light conditions. They found that the plant adjusted its photoprotective processes based on the amount of light it received.