A marvel that I got to see, or rather, got to see through, while in Austria last month during the Retromania tour: the Kaiserpanorama, in Wels. Only four of these stereoscopic viewing machines are still in working operation, I was told. But they were popular between 1890, when they were patented, through to the Great War. It's like a very slow moving carousel, which shows a sequence of 3 D photographs, 28 in total in this case. Originally back lit by candle light, but now illuminated electrically. As it goes round, you put your eyes to a series of binocular-type viewers and if you stare correctly straight ahead, the two images (taken with a special double-lensed camera) mesh to form a solid-seeming image. In this case, Wels street scenes from the end of the 19th Century or early 20th Century--ladies going shopping, workers and tradesmen, kids playing or splashing in the public swimming baths etc - that feel very real, except not real, because they're in faded black and white, and also sometimes have an occasional tear or discoloration in the image that glitches through the 3-D illusion. A right haunty feeling.
You don't get the effect at all from watching this Youtube mini-doc