Fig. 2From: Laboratory investigation of earthquake lightning due to landslidePhotographs of photoemissions from a granite, b pyroclastic rock, c biotite-bearing rhyolite, and d limestone. Note that the scale in b and d are enlarged with increased brightness to make the photoemission patterns easier to see. The RGB intensities on a scale of 0 to 255 are also noted in a–d. All RGB values are based on the original brightness of the photos when they were takenBack to article page