Not a Hologram

Trendhunter is carrying a story about a fashion show that was recently staged by Diesel for their 2008 Spring/Summer Collection. They lead with the headline Holographic Fashion Show – Diesel’s Fashion Show Adds New Dimension and breathlessly claim (undoubtedly cribbing from the Diesel press release) that this it ‘the first time that holograms have been projected along a traditional catwalk’.

Dear oh dear. It looks like the Reverend is obliged once more to step into the fray with his Big Stick of Reason and bash a few heads with it.

The Claim: That this runway show is using some fancy-schmancy system to make holograms of digitally created underwater creatures swirl around and ‘interact’ with the models.

The Implication: That you will see fully realised holographic 3D images floating in ‘thin air’.

The Actuality: The system being used is a simple theatrical trick more than a century old, even if it does use some clever hi-tech riffs. It is not holography.

For starters, this isn’t even the first time that a fashion show has used this particular technique on the catwalk, so Diesel’s trumpeting of this great new idea is a tad overblown. Last year in August, an Alexander McQueen show conjured a ‘holographic’ Kate Moss as the finale to their fashion spectacular. It was done pretty much the same way as this effort, although on a smaller scale.

Here’s a vid of the Diesel presentation from YouTube. You only need to watch a bit of it to get the idea.

Now, I want to say at the outset that I don’t aim to diminish the achievements of the clever technical people and artists behind this show. The effect they have created is pretty cool, for what it actually is. Which is not anything to do with holograms.

The trick they are using here is a variation of an old stage illusion called Pepper’s Ghost. If you have been to Disneyland’s Haunted Mansion you have seen this effect in the Ghostly Ballroom.

There’s a very comprehensive explanation of the Pepper’s Ghost illusion at Wikipedia, but it’s an easy enough idea to understand. Have you ever stood in front of a window at night, and looked outside into the lit street and seen your reflection superimposed over the view? That’s how Pepper’s Ghost works.

In the classic method the audience in a theatre is looking through an angled piece of glass at a dimly-lit stage. The glass is unlit, and therefore completely invisible. In the wings of the stage is a blacked out area with lights that can be dimmed. An actor dressed in light-coloured clothing stands here waiting in the dark, and when the lights come up, the audience sees a full-sized transparent ghostly apparition in front of their eyes, apparently right on the stage (it is a reflection, in the glass, of the now illuminated off-stage actor). The actor can move within the confines of the off-stage black set, and even interact with onstage characters with some minimal preparatory choreography. If you don’t know what you’re seeing, it’s a pretty neat effect.*

The Diesel show isn’t using exactly this technique. My guess is that it exploits a combination of the Pepper’s Ghost principle and the use of a synchronised video projection system on screens below and right along each side of the stage.

This is how I think it works: look closely at the runway in the Diesel show. You can just see a hazy barrier that runs all the way along the stage between the audience and the models. I’m guessing that it’s some kind of glass, or perspex or possibly plastic film. Something clear and reflective. It would have been humungously expensive and a real bitch to set up. It’s angled from the floor at the side of the runway over the heads of the audience. The makers of the illusion boast that it’s the first time that this kind of illusion could be seen from both sides of the catwalk at once – that would be impossible using the conventional Pepper’s Ghost with just one piece of glass. I think therefore, that there are probably two reflection panes, and if you look even more carefully at the YouTube vid you can see a thin line at the top of the heads of the models that is probably the edge of the pane on the other side of the catwalk, conducting a little bit of internal reflection inside the glass. Note that this thin blue line is behind the models, and all the other images are in front of them. Having two panes of reflection would require two synchronous video projections, one on either side of the runway†. Because of the properties of this kind of reflection, the audience only sees an image on their own side, and not the one on the opposite side. Optically, the projected images would appear to be the same distance from the glass pane as the pane is from the projection screen. Probably in this case, the floating creatures would seem to occupy centre stage with the models.

The projection equipment and the screens are lower than the audience (maybe some of it is under the runway) and hidden by barriers that run all the way along the sides of the stage. The models can ‘interact’ with the images because they can in all likelihood see the projection screens down the right and left of the catwalk at their feet.

Here – I made a little animation that shows how it could be achieved:

The projected image is mostly likely corrected for the distortion of the slanted screens (unlike my example) and despite the claims of viZoo, who invented the technology‡, I don’t for a moment buy the idea that the image you are seeing is 3D. It might be a 2D projection of a rendered 3D object, but it is not 3 dimensional looking in the way that a real projected moving hologram would be (if you could actually do such a thing, which you can’t).

It’s a really, really clever piece of wizardry, for sure, but it isn’t done with holograms. And it reminds us that some of the best ideas are the very simplest.

Oh, and the clothes? No, I didn’t notice them either.


*I once saw the technique used in a Star Trek show at Universal Studios where members of the audience were dematerialized in the Enterprise ‘transporter room’. It was a marvellous effect and I was so unprepared for it that I was completely flummoxed for a second or two.

†Or, perhaps, some kind of prismatic image splitter on each projector to make two identical images, one for each side.

‡And who, incidentally, never once claim on their site that their system creates holograms.