This ghostly face appears to mysteriously change its features when you look at it for a while (some viewers said they have experienced traumatic visions!). Moreover, if you unfocus your eyes and just look steadily through the image, you will notice that after approximately 10-15 seconds the face gradually disappears…
Ghost Faces / Apparition – Mixed media (2011)
This spooky portrait is made by merging together 50 common human faces. The process of averaging multiple exposures of human faces isn’t really new. Already in 1879, Sir Frances Galton was experimenting with this photographic process. Others followed, and borrowed this technique for artistic or social purposes: Ken KitanoJason SalavonDonald Scott Bray

But why does the face change and / or disappear? The mechanism underlying this illusion is neural adaptation, as in Troxler fading, combined with the ensuing filling-in being driven by face circuits. Read more.

I enhanced the apparition of multiple distinct faces just by animating two frames indefinitely, as shown in the gif below. Although the face of each frame is identical, the resulting human face seems to morph and move.
Apparitions
Published:

Apparitions

Published: