The great director Martin Scorcese once said that cinema is a matter of what's in the frame, and what's out. Wise words indeed.
But sometimes it's the tell-tale details in the background of a shot that tells a story with far more subtlety and care, compared to what's in the foreground and shoved in our faces.

A good cinematographer knows what to include in a shot, and how to nest clever clues and foreshadowing so that you don't pick up on them until your fourth or fifth rewatch.
Of course, sometimes the opposite can happen, and an innocuous blooper can take on a life of its own when seen in bad lighting, or from the wrong angle.
So without further ado, here's our rundown of the eight scariest background details in movies. Warning: there are spoilers ahead!
1. The Exorcist
The Exorcist is already regarded as one of the scariest horror movies of all time. But when you know the backstory behind one of its extras, it takes on a disturbing new level.
In the scene where Reagan is undergoing a carotid angiography procedure, director William Friedkin filmed it at the New York University Medical Center using real x-ray technicians.
The bearded man you can see in the background is one of these technicians, Paul Bateson – a real life serial killer who was later arrested in March of 1979 for the homicide of film critic Addison Verrill.
Police investigating the murder of Verrill subsequently uncovered evidence that Bateson was a serial killer responsible for the murder of six other men in New York City between 1977-1978.

2. Poison
The Rosanna Arquette TV movie poison tells a typical tale of murder and suspense. But in the process, it inadvertently captured something genuinely inexplicable.
If you look up to the top right-hand corner of the screen in the scene where Arquette's character dumps a car into a bond, you'll see two mysterious white circular objects zoom through the sky.
Yes, that's right: genuine UFOs!

3. The Wizard of Oz
The saccharine 1939 musical The Wizard of Oz is probably the last thing people would think of when it comes to spooky movies.
But for years, a rumor persisted that, in the background of one shot, one of the dwarf extras who played a munchkin can be seen hanging from a noose from one of the prop trees, after taking his life on set.
Thankfully, an enhanced version of the film shows that the 'hanging munchkin' is actually just a harmless prop of a bird. Phew!

4. The Post
The Post isn't a horror movie at all, telling the story of The Washington Post newspaper's attempts to bring down President Richard Nixon.
But in one scene in which Meryl Streep attends a protest, one of the background figures in the scene appears to be a motionless ghostly figure wearing a white veil over their face.
However, there is a mundane explanation for the spooky specter. Rather than a supernatural oddity, it's actually meant to be a period-accurate anti-war protestor, at a time when many dressed as ghosts to symbolize dead soldiers and civilians in Vietnam.

5. Three Men And A Baby
Similarly, for a number of years, moviegoers who watched the 1987 comedy, Three Men and a Baby were convinced the ghostly image of a boy who died in the home where one scene was filmed could be seen lurking behind some drapes in one scene.
However, according to Snopes, the 'ghost boy' is actually a cardboard cut-out of actor Ted Danson, which was hidden in the background of the shot as a prank.
The cut-out referenced an ironically cut sub-plot from the film, in which Danson's actor character appeared in a dog food commercial and ended up with a number of cardboard stand-outs of himself.

6. IT: Part One
There's no doubt that IT is a movie that sets out to scare and succeeds. But one of its creepiest moments is also one of its most subtle.
Look closely at the scene where Ben Hanscomb visits the Derry library to read a history book, and halfway through you'll see the formerly friendly elderly librarian standing up and fixing the young boy with a terrifying rictus grin.
It's hard to make out, it's never brought up again, and certainly isn't explained. What's going on? We have no idea. But it gives us the heebie-jeebies nonetheless.

So if you don't believe that some of these eerie background details are legit, then don't just take my word for it. Give them a rewatch and look closely, and maybe you'll find something you've never seen before...