History Main / PerceptionFilter

* ''Literature/FatherBrown'':
** Invoked in one story. Nobody takes this explanation seriously.
** Another variant, fully realistic and closer to HiddenInPlainSight, appears in an aptly-named "Invisible Man".

* Witches in ''Literature/HisDarkMaterials'' can do this with magic, but it isn't foolproof. Will Parry figured out how to do the mundane version of this.

* ''VideoGame/TheHayseedKnight'' has this PlayedForDrama in the form of Oblivion, a magical {{curse}}. It works such that normal people who are introduced to sufferers (notably [[spoiler:Eina and Sep]]) completely forget about meeting them and any relationships they have if they stop making regular contact with the sufferer, making long-term relationships very difficult and causing great angst. It doesn't affect certain immortals, though, and can be counteracted if someone or something else the forgetful one already knows about reminds them of the cursed one's existence.

* ''VideoGame/Persona5Royal'' has an example that works mainly on the person it affected. [[spoiler: The girl you've known the entire game as "Kasumi Yoshizawa is actually her sister Sumire, living out the identity of the deceased Kasumi. Her therapist, Dr. Maruki, used his knowledge of the Cognitive World to effectively brainwash her into thinking she was Kasumi so that she would no longer be heartbroken over her sister's "meaningless" sacrifice to save her. The main reason it held is that, every time Sumire heard someone say her name, she just heard "Kasumi." The only reason ''you'' know her as Kasumi is that you found her notebook with Kasumi's name on it.]]

[[folder:Web Comics]]

* It's used to explain how the CelebrityParadox can exist in "A Time To Kill" (a fancomic from ''Webcomic/RichsComixBlog''). The Tenth Doctor tells Donna that "the combination of sounds, vowels, consonants, cadence" of the ''Film/JamesBond'' standard introduction ("BondJamesBond") acts as an audio perception filter, meaning that Bond can introduce himself to people and they won't remember details about him, including the fact that he's the living embodiment of what ''should'' be a fictional character. Then, to demonstrate, the Doctor uses the line on Donna, and she instantly forgets everything he told her about Bond.

* ''{{Webcomic/Wychwood}}'': Julian has cast a spell on his house to keep Wychwood from noticing that it's occupied and maintained, and keep any passerby from taking note of the house at all. It keeps unwanted visitors away and [[spoiler:he stops maintaining it and marks the house as a safe house with supplies for other survivors when they have to flee]].

* The [[MonsterOfTheWeek gamma]] in ''Literature/ShadowUnit'' Season 1 Episode 7 "Overkill" had this as a superpower.
* In ''Literature/TalesOfMU'', the gnomes have this as an unconscious ability, and it tends to get stronger the more of them that are together. A gnomish professor has to remind her class she's there and is completely ignored by the administration.
* ''Webcomic/ViralByCommittee'': As far as we know Alex can see just fine what happens around them, but other entities have filters all over the place. The Nulls are initially [[spoiler:cut from the nanite network]] by the Liminal Quarantine, the [[spoiler:zombie nanites]] see through a filter that scrambles faces and text[[note]]but ironically not CAPTCHA text, because ''the filter doesn't notice it's text''[[/note]], the Committee is first seen through a filter [[spoiler:making them look humanoid]], and in the second chapter Alex is explicitly dreaming, which greatly distorts what they see.
* One girl in the Josie stories of the ''Literature/WhateleyUniverse'' has this. When she goes to the police station to turn in a criminal, the police keep not noticing her, to the point that she finally has to dictate her account on a tape recorder and leave it with a note saying "play me".

* Derren Brown played this trick on a film student in [[https://www.youtube.com/watch?v=VTobS-09fBQ this video.]] All he does is speak a bunch of nonsense, then add "You just simply don't see me." Then he intentionally plays out a scene from the 1933 ''[[Film/TheInvisibleMan1933 The Invisible Man]]'' film. The camera focuses on the student's face a lot, and you can see how his vision is deliberately unfocused, as if he can't help it, and how freaked out he is when Derren picks up a doll, as if the doll is moving on its own.
* Snipers use what is called a ghillie suit, which is essentially random scraps of cloth and burlap, often augmented with local leaves and twigs. It breaks up the lines of the human body, making it extremely difficult to see them. Though meant as a long-range disguise, snipers have reported patrols and guards (even ones ''actively looking for them'') that walked right past them, sometimes so close they were almost stepped on. A documentary on sniper training demonstrated this when it focused on a small, grassy clearing in the forest...and then the graduates in the course stood up. The clearing was essentially wall-to-wall snipers. That also demonstrates the potential flaw of the suits - moving will generally make them useless as people's eyes will be drawn to that movement and be better able to take notice of the general shape of a person moving around that they wouldn't while a ghillie suit wearer is still.

* ''Manga/AyakashiTriangle'' has a general WeirdnessCensor that [[GodInHumanForm jinyo]] are able to specifically manipulate {{muggles}} to blend in. When Shadow Mei started attending school as Suzu's cousin, not only does everyone believe it, they act as if she'd been around for a long time. Hinojiki clearly looks like a child, but is able to convince people he's just a short twenty-year-old. It also seems to work unconsciously, as after Hinojiki visits and leaves the school, none of them remember he was ever there.

* In ''[[https://www.fanfiction.net/s/13435630/4/Harry-Potter-and-the-Artificer-Legacy Harry Potter and the Artificer Legacy]]'', one of Harry's first inventions is a "Hiding Stone" which can be placed on a door to make it less noticeable to anyone not attuned to it. However, it only dissuades the mildly curious and anyone seriously looking for the door (or the person on the other side of it) it hides will be able to see through it, as Harry explains to Tonks when she requests one for her room.

* In ''Webcomic/ElGoonishShive'', Immortals conceal themselves via magic when not intentionally manifesting themselves to humans and/or other Immortals. Pandora notes in the ''Question Mark'' arc that each immortal creates their own, making it so that multiple Immortals can all be observing the same event and still be unaware of each other's presence.

* ''TabletopGame/Warhammer40000'': Corvus Corax, the Raven Guard Primarch, had this as a psychic ability allowing him to remove himself completely from living creatures' consciousnesses, which only helped him in being a StealthMaster. Even automated sensors aren't immune, as one Night Lords Captain was rather perturbed to realise that not only did his armour fail to detect Corax before he'd approached them, his helmet's augur sensors weren't registering anything despite Corvus being ''right in front of him''.

* The Grey Men in ''Literature/{{Momo}}'' can do their work effectively because they are visible but inconspicuous. They can reconnoiter without being noticed, or persuade people into saving time without being remembered.

* In ''Fanfic/AshesOfThePast'', for some reason, there's one applied to [[spoiler: the entirety of Team Galactic; they can operate in plain sight and no-one will see, hear or even notice anything odd is going on. Only Ash and those he has Reminded of the old timeline are immune to the effect, but considering all the new Pokémon he has, that still only amounts to around half of his team and a scant handful of his new Legendaries.]]

The {{Trope Namer|s}} is ''Series/DoctorWho'', more specifically a piece of circuitry of the same name, which allows the Doctor's TARDIS to blend into its surroundings, no matter what form it takes on landing. Even in its iconic anachronistic police box form, it's been stated that it can shift the perception of the person looking at the TARDIS to make them not notice it unless they actively try to.

The TropeNamer is ''Series/DoctorWho'', more specifically a piece of circuitry of the same name, which allows the Doctor's TARDIS to blend into its surroundings, no matter what form it takes on landing. Even in its iconic anachronistic police box form, it's been stated that it can shift the perception of the person looking at the TARDIS to make them not notice it unless they actively try to.

* ''Series/DoctorWho'' is the TropeNamer.

** Pocket Watch, [[Anime/{{Pokemon}} a hypno,]] puts a light mental suggestion on people to not to look at Ash to closely when he went to school.

* Snipers use what is called a ghillie suit, which is essentially random scraps of cloth and burlap, often augmented with local leaves and twigs. It breaks up the lines of the human body, making it extremely difficult to see them. Though meant as a long-range disguise, snipers have reported patrols and guards (even ones ''actively looking for them'') that walked right past them, sometimes so close they were almost stepped on. A documentary on sniper training demonstrated this when it focused on a small, grassy clearing in the forest... and then the graduates in the course stood up. The clearing was essentially wall-to-wall snipers.

* ''Videogame/XenobladeChronicles3'': It's implied that the inhabitants of Aionios are all under this from birth. The two armies are born from PeopleJars and spend their very short lifespan only warring and doing war-adjacent tasks. The characters seem to have no perception of gender as it is only after they stop being under the effect of the Flame Clock that they start feeling shame at being seen naked by other people, especially the opposite sex. They also don't realize the physical differences between each other, like Sena's glowing power lines in her skin and Lanz's metalic skin.

Your standard {{Invisibility}} typically makes you transparent to light. While quite effective, it does have a number of catches, such as retaining the ability to be heard or otherwise detected, possibly forcing you to be an empty-handed InvisibleStreaker, or even rendering you blind if it works realistically.[[note]]Your eye works by absorbing light energy and converting it into electric impulses in your nerves. Thus, ''if your eye itself, with the retina and all, were to be transparent'', it would mean no light absorption, causing no electric signals being generated and making you blind.[[/note]] In short, it won't make you stealthy overnight.

Your standard {{Invisibility}} typically makes you transparent to light. While quite effective, it does have a number of catches, such as retaining the ability to be heard or otherwise detected, possibly forcing you to be an empty-handed InvisibleStreaker, or even rendering you blind if it works realistically.[[note]]Your eye works by absorbing light energy and converting it into electric impulses in your nerves. Thus, being transparent means no light absorption, causing no electric signals being generated and making you blind.[[/note]] In short, it won't make you stealthy overnight.

* ''Film/{{Stardust}}: Variation: One of the {{Big Bad}}s puts a spell on Ditchwater Sal that makes her unable to see, touch, smell, or hear the Star. When Yvainne (aforementioned star) and Tristan approach Sal for passage to the Wall, she not only cannot perceive Yvainne, she can't even be touched by the star-turned-human when she tries to attack Sal for turning Tristan into a rodent.

-->'''Jimmy Woo:''' ''[to two cops outside Westview]'' Pardon me, Sheriff. Would you mind repeating your claim about Westview to my colleague here?\\

* In the first installment of ''ComicBook/TheBojeffriesSaga'', a council worker knocking on the family's door to demand a century's worth of rent arrears is blamed on the "curiosity damper" breaking down.
* One of the many ways that [[ComicBook/{{TheInhumans}} Inhumans]] kept [[HiddenElfVillage Attilan]] hidden from humans is circuitry built into the surrounding area that telepathically suggests to them to change direction and hike away from it.
* Agent "!" of the Brotherhood of Dada (antagonists of the ''ComicBook/DoomPatrol'') has the power that he "comes as no surprise", i.e. nobody finds his appearance or presence particularly unexpected or notable, so people tend to ignore him. Given that he's dressed in a suit of exclamation marks and his chest is a gilded cage with a small airplane in it, this is quite an accomplishment.

* An episode of Syfy Channel's ''Series/{{Alphas}}'' had a woman named [[MeaningfulName Gri]][[ShoutOut ffin]] whose power is essentially this, although it is presented as traditional {{Invisibility}}. Rosen postulated that her powers operate by allowing her to hide in blind spots of those who look at her.

* An episode of ''Captain America'' used a gadget created by the Red Skull, which emitted high-frequency sound-waves to make mooks invisible to people.
* In ''Series/DarkAngel'' one man turns out to be a genetically engineered precog with a "stealth frame". People avoid eye contact with him and willfully forget that he's there.

* ''Series/PersonOfInterest'': On the season 3 finale, [[spoiler:Root reveals that the Machine's plan has not been to defeat Samaritan; Decima Technologies is simply too powerful, and the best that can be achieved is to keep Team Machine safe. Root and the Machine therefore set up a perception filter so that Samaritan ignores the new cover identities set up for the team (and a few programmer allies of Root's).]]
* ''Series/RedDwarf'': In "M-Corp" the Jupiter Mining Corp is bought out by the titular M-Corp who install a perception filter in Dave Lister's brain. As a result, anything on board the ''Red Dwarf'' that isn't owned by M-Corp becomes invisible to him. This includes his fellow shipmates as Cat isn't an employee and Kryten and Rimmer are, respectively, a droid and a hologram running on tech from other companies.

** A villain in the episode "Unrequited" could make a blind spot appear in the middle of people's eyes and hide in it: People could see everything around it, but when trying to look directly at him, didn't see anything and their brain extrapolated the world without him.
** In the episode "Badlaa", a murderous Indian mystic is able to disguise himself as a janitor or simply appear invisible.