I don’t know how common this type of ad is, but sometime around 2010 I was sitting next to a window on the L.A. subway when this animated ad for the movie Coraline appeared in the window.
I think I get the basic idea here. The successive images of the scene are projected onto the walls of the tunnel, and you see them in order as the train speeds past. However, what I don’t understand is why this method of animation works. I thought in order to utilize the persistence of vision effect, each still image has to be kept stationary with respect to the viewer for a split second, before the next image is displayed. Otherwise, as I understand it, we would see a mere blur of images, like when an old-school film is improperly threaded in the projector.
Since the train obviously can’t stop 20 times a second or whatever, so the images are still, how do they make this work in a subway tunnel?
For those who haven’t seen it, here’s a YouTube video. It looks like this is in the DC metro, but I think the ad was rolled out to every subway system in North America. The idea was probably revolutionary at the time, but I don’t think it caught on.
I had this whole long reply written, mostly trying to understand where the OP’s confusion was coming from. I couldn’t understand why the OP thought strapping a projector to the roof of a subway train would be an issue. Then I read your article. I guess I’m the one that’s confused. I found a video of how this works. It’s using images painted on the subway wall, the ones in the OP’s link must be individually projected images. Same effect though, I think.
So it is exactly the same mechanism as the antique drum-type zoetropes, except stretched out in a line.
In the video posted in the OP, the shutter appears to be more like the slats of a venetian blind, so you can only actually see each frame perpendicular to its plane - thus mitigating the smearing you would get if it was just a series of images with no shutter.
By 2010, it would have been around for awhile. We had these in Budapest c. 2001. I had wondered whatever happened to them. I’ve never seen it in North America and had no idea they were tried out here for a spell.
San Francisco’s BART also at least tried zoetrope ads—they were there when I moved to SF and I assumed they’d always been there, although apparently it started in 2007. There’s an example linked in this post that looks a little janky, although my recollection is that this is true to life and not an artifact of YouTube.
I’m not sure they’re still around or, if not, how long the experiment wound up lasting. But at least, for a data point, that’s another American mass transit system that used them.
In one of the auto suggested threads, a user mentions them being in Chicago in 2006, so that’s another system. I live here and I guess I wasn’t taking the subway portions of the el enough to see them.
Like others said, the slats perform the shutter function to only allow you to see one still image at a time. If we just dragged a length of motion picture film across a projector lamp but without the flickering shutter, we’d get the blur like OP described from transitions between frames. The forward motion of the car keeps telltale parallax down and framerate high enough the pull off the illusion.
I suppose the page transitions in a flip book animation serve this purpose as well. It seems, as in this case, the transition is much less discrete than with a movie projector. The consistency of image elements must be dominate over the blur of movement of curling page transitions or interstitial portions of yhe viewers experience on the train.
They had an ad like this on the Montreal Metro between Peel and McGill stations back in the 70s. So it’s definitely not new. I even remember what it was advertising: Direct Film, a long-defunct photo store.
