Though it’s not technically a hologram, Engadget explains the technology (or optical illusions) behind the appearance of Tupac Shakur at Coachella in 2012, and Michael Jackson at the Billboard Music Awards last week.
They write, “The holographic people we’ve seen are based off of an illusion called “Pepper’s Ghost,” developed by Henry Dircks and John Pepper in 1863. The concept requires two rooms, some specifically placed glass and carefully controlled lighting. A room adjacent to the viewing area (or stage) is set up as a mirror-image of the area the audience sees; if there’s a chair on the right of the stage, it’s on the left in the other room. The key difference is that other room is either painted black or entirely unlit, so as not to cast any unwanted reflections that would break the suspension of disbelief. That room is where the performer resides. The stage area must be brightly lit at first for the whole thing to work. Then, the stage’s lights are dimmed slightly and the lights are raised in the mirror-image room, which causes the not-physical performer to appear.”
Read the full story here.