A ghost in the machine

“You like photos,” said B our decorator yesterday, opening his smartphone.
It revealed a derelict church. I am disappointed. I expected something better.

“Where was it taken?”
“Somewhere near Fort William.” (west coast of Scotland).
 I am puzzled. What’s so special about it?
“Watch this.”

He enlarges it.
“Look in the window. Top right hand side.”
Suddenly a skull appears.  ( see extra).

Now I don’t believe in the supernatural, dismissing it as the brain playing tricks.
“Did you take it?”
“No, I was working with this guy who happened to be a keen photographer . He didn’t know what to make of it.”
“He said he only discovered the image after he put it into his computer and enlarged the photo”.

Naturally I ask for a copy.
Sure enough only when I enlarge it does the skull appear.
 But the eerie thing is that it does not become pixelated like the rest of the photo.

Try it for yourself. See if you can work out what’s is going on.