Hologram or not

There's been talk in the press lately about '3D holograms' - but why the quotation marks? In fact, most of the recent productions claiming to be holograms are not actually holograms, and often not 3D either.

Call it smoke and mirrors, and mylar foil. The holographic effect recently being touted as revolutionary is actually a variation on an illusion called Pepper's Ghost that was popularised in the 1800s. Pepper's Ghost relies on clever staging to position a reflective surface between the audience and real objects in a scene. In the 1800s John Pepper used plate glass to reflect a ghost (hidden offstage) but today's practitioners use transparent mylar foil and high powered video projectors. So when you hear about Michael Jackson being "resurrected in 3D" for the Billboard Music Awards, Gorillaz performing live on stage or even Indian Prime Minister Naverenda Modi campaigning as a 3D avatar what this actually means is that video content is projected onto a transparent screen (mylar foil) positioned at 45 degrees to the audience. We perceive part of this invisible screen to be in front of the other and so accept the illusion better than if the screen was hung vertically. It worked in India. Modi's 'hologram' by NChant3D helped him win office and a place in the Guiness Book of World Records for simultaneous broadcasts to 88 stages around India.

Lawyers are doing rather well out of the Pepper's Ghost effect. There are several different patents in operation and considerable dispute over who has the right to use what techniques where. Hologram USA and Pulse Evolution have exchanged lawsuits in the US courts over who had the rights to stage the Michael Jackson show. UK company Musion, whose system is at the centre of this particular dispute, has filed US and European patents and licensed its Eyeliner technology to NChant3D for Modi's campaign.

Meanwhile other productions side-step the legal issues and use semi-transparent DILAD screens to rear project characters, most notably Crypton Future Media's shows starring their virtual pop star, Hatsune Miku. For some entreprising Japanese fans, the beloved pop star is brought to life in the living room by projecting onto mosquito net.

So what of real holograms? Holography uses lasers to record light in such a way that we perceive the recorded image as having three dimensions in space without the need for any screen to be projected onto. 

Screen producers have a bunch of different options for immersive visuals but real holograms aren't quite ready for prime-time. What R2-D2 manages to do so effortlessly in Star Wars movies remains a long way off... this week.

Image credit: Kevin Winter/Billboard Awards 2014/Getty Images