This is a very strange phenomenon that would be hard to explain. And thanks Gaet for asking the good question. WHY only on the face? Why not the all body? Why only him? I mean, that’s obvious… We are Not Aloneee…
The poster uses glossy black ink, which reflects the flash. The camera is in a position where the flash is pointed directly at the man in the poster, so light flashes straight back. But the other people in the poster are at an angle to the flash, so the light bounces away, rather than back.
Could be a relection ,but I think it fake. Its no a young guy either its an older man. Maby a man was there looking at them and somehow a light reclection did this,but I dont think its a ghost. If it is then its a ghost with humor.
Its a flash glare
You can see the flash that was on the camra on the people
also this is a glossed poster
the “ghost” is the man in the middle of the poster
the ghost is also in the centre of the picture, so, it flash would be directed at his face