text: Biophotons may be detected with photomultipliers or by means of an ultra low noise CCD camera to produce an image, using an exposure time of typically 15 minutes for plant materials. Photomultiplier tubes have been used to measure biophoton emissions from fish eggs, and some applications have measured biophotons from animals and humans. Electron Multiplying CCD (EM-CCD) optimized for the detection of ultraweak light have also been used to detect the bioluminescence produced by yeast cells at the onset of their growth.
  The typical observed radiant emittance of biological tissues in the visible and ultraviolet frequencies ranges from 10 to 10 W/cm with a photon count from a few to nearly 1000 photons per cm in the range of 200 nm to 800 nm.