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I have seen various articles and / or videos about a billboard in London for a BBC series about Dracula and its clever use of light and shadows. During the day, the billboard looks like this, with bloody stakes stuck into a white billboard:

Image of Dracula Billboard with stakes

As the sun goes down, a shadow in the form of Dracula's silhouette appears, apparently cast by the stakes:

An image of the Dracula billboard at night, showing a silhouette of Dracula's head

All the articles I've seen on this seem to be making the claim that the silhouette is produced by shadows cast by the stakes, and the placement of the shadow and the stakes certainly seem to indicate that this what the ad wants to show you, but I am skeptical of the claim that the silhouette is actually being cast by the stakes. For one thing, the silhouette is very even, with no gaps or overlaps, which seems implausible (and to some extent unnecessary to create the desired effect).

For another thing, there is only one light source, but if you look closely, you can see shadows cast by the individual stakes:

Highlighted shadows cast by individual stakes

I'm also finding it hard to imagine how they are supposed to have created the detailed teeth light that with a single light source cast on some stakes. I suspect that this is actually being achieved by a hidden light source projecting from the front of the billboard, with a Dracula silhouette in front of it, but I have found very little in the way of skepticism about this claim — all the articles seem to accept at face value that the stakes are casting this shadow.

Can anyone give more definitive answers as to whether this is actually being produced as described?

Edit: Just noticed that one of the stakes has little teeth dangling from it, which might explain how the teeth are allegedly being produced:

Close-in image of Dracula teeth hanging from stake

I also found this video where someone claims to have created a 3D model to recreate it, and it certainly seems to be doing a passable job (assuming that the lighting is the result of ray tracing on the 3D model and not a digital effect), so maybe it's more plausible than I thought?

Edit 2: I realized belatedly that with the premise that there is a single light source it doesn't really make sense to say that there are "no overlaps", since these are opaque objects, so that source being blocked by two or more objects would look the same as it being blocked by only one object.

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Here is a timelapse reveal of the effect. The shadow appears to be created by the light on the left.

For another thing, there is only one light source, but if you look closely, you can see shadows cast by the individual stakes:

As seen in the video, the angle of those shadows is wrong for the light on the left. They're coming from a different light source out of frame. This video of the billboard does not have those shadows.

For one thing, the silhouette is very even, with no gaps or overlaps, which seems implausible (and to some extent unnecessary to create the desired effect).

It would only be implausible if the stakes were not specifically arranged to produce the effect.

The BBC picture reveals small imperfections in both the edge and gaps.

enter image description here

I suspect that this is actually being achieved by a hidden light source projecting from the front of the billboard, with a Dracula silhouette in front of it.

Such a projector would be immediately obvious to anyone present.

This would be more difficult. It requires leasing two locations, one for the billboard and one for the projector. A projected shadow amplifies any misalignment. The shape, distance, and angle of the projection must be exactly right so it could not be prepared beforehand. The shadow would be projected onto the billboard and the stakes placed on site to appear to be creating the shadow. Once they got it right it would need to remain in perfect alignment night after night.

And then there's motive. Why fake an effect nobody was expecting in the first place?

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  • The close-up video does make this seem much more plausible (particularly since that person would probably be able to notice a front projector). Time lapse is not playing for me for some reason.
    – Paul
    Dec 14 '20 at 21:02
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    @Paul The time lapse video didn't play for me either, until I temporarily disabled ublock origin.
    – shoover
    Dec 14 '20 at 21:15
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    The subtlety is that the lamp creates both direct lighting resulting in the strong shadows you've zoomed on and reflected diffuse lighting one from the surface of the board/poster. It's the latter that creates the larger shadow, possibly together with the penumbra from the direct lighting. I'm not sure how to prove it though.
    – Fizz
    Dec 14 '20 at 21:40
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    In the time lapse video, 1) there are short faint individual shadows going in two directions from at least two light sources, 2) the billboard flood comes on, creating the Dracula shadow, 3) another light source comes on, producing the more obvious individual short shadows. By now, the orginal faint post shadows can't be seen. I guess the billboard was designed with just the board-mounted floodlight, and the other shadows are incidental, caused by street lights etc. Dec 14 '20 at 23:16
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    Sure, why not end 2020 with conspiracy theories about a billboard?
    – Schwern
    Dec 15 '20 at 2:09

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