Remember the Tupac "hologram" performing at Coachella that Zeon posted recently? Well, it turns out that Tupac has more in common with the ghosts at Disneyland's Haunted Mansion than with real holograms.
Cyrus Farivar of Ars Technica explains:
This wasn’t a hologram at all. Rather, it was a clever optical illusion technique known as "Pepper’s Ghost," which dates back to a technique first described by an Italian scientist in the 16th century. [...]
So here’s how it works: the audience needs to be able to see into the main room, but not into an adjacent hidden room. In the case of the Tupac "hologram," that’s the main stage where a real-life Snoop Dogg and Dr. Dre were sharing the limelight. However, hidden on stage is a piece of glass, where the images can be reflected from and pushed into a target area that makes it seem like a single room. But off to the side, behind the glass, there’s a hidden room that has the original object being projected.
These days, AV Concepts, the San Diego-based company behind the Tupac performance, uses a proprietary Mylar foil, known as Musion Eyeliner, rather than glass. The company said in a press release on Monday that its on-site server "delivered uncompressed media for 3 stacked 1920 x 1080 images, delivering 54,000 lumens of incredibly clear projected imagery."