(Pocket-lint) - Every now and then an image appears online which has people heartily debating its authenticity, arguing about its colour or asking how it came about in the first place.
There are also some amazing pictures that look like one thing but turn out to be something quite different.
We've gathered together a collection of the best from around the 'net - pictures that'll have you scratching your head, questioning your eyesight and generally feeling perplexed by their existence.
This photograph taken on the beach seems to show the speaker on a floating platform. No doubt down to our brain interpreting the shadow of the flag blowing in the wind as the shadow of the speaker's platform and microphone instead.
Another classic illusion caused by our brains trying to decipher the scene before us.
Duck or Rabbit
This optical illusion has taken on many different forms since it first found its way into publication in a book "Philosophical investigations" by Ludwig Wittgenstein in 1953.
Here it is suggested that there are ambiguous images that can be seen in two (or more) different ways.
In this instance, the drawing could be a rabbit or a duck or both and what you see first will be down to your perception of the world or based solely on suggestion - the duck and rabbit axis in this version make it easier to quickly decipher both variations.
Ambiguous cylinder illusion
One of the finalists for the "Best Illusion of the Year Contest" makes for pretty mind-bending viewing.
If you're left scratching your head after watching that video, you can see a breakdown of how it works here.
Wonderfully weird greyscale store
While out shopping, YouTuber Holly McKee discovered a real-life optical illusion. Nestled away in the children's clothing section she discovered an aisle of black and white clothes that made the photo look like a filter had been applied.
The Black and Blue/White and Gold Dress
Back in the hazy days of 2015, a certain dress took the internet by storm and had everyone debating about whether it was white and gold or black and blue.
The simple garment was the perfect example of an optical illusion that was no illusion at all. It was, in fact, just a scientific demonstration of how the eye sees things differently in varying light sources and how our brains all handle this interpretation in ways that are unique to us.
The non-red strawberries
Like the white and gold/black and blue dress, these strawberries are an optical illusion caused by something known as colour constancy, which is a feature of the way we perceive colours under varying light conditions.
There is no red in the picture and yet our brains clearly interpret the red of the strawberries as still being there – assuming you're seeing them under a blue light source and extrapolating accordingly.
Incredible street artist Sergio Odeith turns everyday corners in the real world into incredible three dimensional artworks with ultra-realistic anamorphic graffiti painted across different surfaces to give the illusion of a depth that doesn't exist.
Letters leaping out of walls, creatures lurking in corners, other worlds coming to life in the corner of a forgotten space. His works play havoc with the eye and create marvellous murals that are a pleasure to behold.
The Bridge to Nowhere
The Storseisundet bridge is one of the largest bridges in Norway and photograph from the right angle it gives the impression of being a bit of road that comes to an abrupt and dangerous end some 75 feet above the ground.
However, the bridge is actually a cantilever design with a curve to it that simply makes it arc away into the distance.
Anamorphic advertising artwork
In 2013, eyewear manufacturer Ray-Ban teamed up with optical illusion masters Brusspup to create an ad campaign which included anamorphic illustrations which look like real three-dimensional objects from the right angle.
The globe and baseball are the standout pieces of this artwork and we think they're thoroughly impressive. For more optical illusion goodness, check out Brusspup's Youtube channel.
Neck or back?
In 2018, Twitter user @LilMaarty posted this image, apparently confused over whether the photo showed a woman's back or just her neck. The Tweet was the subject of much debate and was retweeted over 30,000 times. It turns out it is her back, in case you're wondering.
First, we had the dress, then we had the shoe. In 2017, an innocuous photo of a trainer was posted online in a Facebook group. The poster wanted to know what colours people saw - pale pink and white or blue and grey. It was a subject of much debate and had Twitter all in a flap too. It was eventually revealed that the trainer is, in fact, pink and white, if you saw anything else it was a mere trick of the light or down to how your eyes perceive colours.
The Infinite Chocolate Bar
This tasty illusion apparently shows a way to get never-ending blocks of chocolate out of a single bar. Alas, it's all a trick and simply involves a shorter and shorter bar. Still pretty clever stuff!
Another brilliant optical illusion created simply by the sun being at a specific place in the sky. This one seems to show oddities in the windows caused by their shadows which makes the building look like it belongs in Inception.
Wooden Train Track
In another Tweet-storm, yet another optical illusion based on an everyday object appears to confound logic and physics. One wooden train track block is apparently longer than the other, yet when put on top of the other, they're the same length. How?
The solution to this apparent mystery is contained within the replies to the initial Tweet, but we'll let you enjoy it in the meantime.
The Negative Lady
This illusion requires you to stare at the white dot on the woman's nose on the left for 15 seconds, then look to the right of the image at the blank space. You should see a flicker of the full colour photo of the woman.
This is down to the way our brains interpret imagery and colours and in this case is known as "negative afterimage", which was explained by Dr Juno Kim from the University of NSW School of Optometry and Vision Science to Daily Mail Australia:
"The code for all the hues we can experience in the light spectrum – this information is relayed from the back of the eye to the brain via three opponent neuron channels.
"When you look at something that, for example, is yellow for a long period of time, you stimulate the cells that are positively sensitive to yellow – so in the yellow and blue channel.
"The cells’ activity increases and after a bit of time the activity fatigues and declines.
"When you then direct your gaze at a uniform background – let’s say a grey wall – then what happens is that the cell doesn’t return to its resting activity, it goes much lower than that.
"It’s that decline – the weakening of the yellow code – that codes for the opposite colour to become stronger, so you’ll see blue."
The awkward dots
A simply brilliant image that plays real havoc with both your eyesight and your brain. This image was shared by Will Kerslake on Twitter with the caption "There are twelve black dots at the intersections in this image. Your brain won’t let you see them all at once."
We have managed to see them all, but it's not easy.
Shiny legs or paint
This is an unusual illusion, at first glance you'll probably spy a pair legs that seem to be covered in oil, but given a second to look again and you'll see they're actually spattered with white paint.
Video game or real life?
This image was taken in Hawaii and shows a weird time of day when the sun is at such a perfect position in the sky that no shadows appear near these posts. The result is what looks like video game rendering rather than real life. You have to look a few times to establish a firm sense of reality with this one.
iPad Car Seat
Sometimes an illusion can be as simple as a pattern blended into another in the same way that camouflage works.
This photo was posted on 9gag with the headline "Just spent 30 mins searching for my Dad's iPad" – can you spot the hidden tablet in the photo?
The four eyed man
As far as optical illusions go, this one is both simple and painful. Whoever thought two pairs of eyes and two mouths would be enough to break your brain and make it painful to focus?
This photo appeared on Imgur and caused a bit of a splash. A little girl appears to be jumping into a swimming pool while simultaneously blowing bubbles like she's already underneath the surface.
Commenters quickly pointed out that her hair is dry and the apparent air bubbles could just be droplets of water from the splashing, but no conclusion was reached as to what was actually happening.
So many questions.
Log or dog?
A simply perfectly timed photo of a pooch having a rest near a felled log. The result is a mild optical illusion which makes it look like the dog has either been sawed in half or is a break in the make-up of reality. Barking mad.
The revolving snakes
This one is a simple trick of the eye. This is not an animated picture, it's a static file that shows a mass of intertwined snakes. But if you stare at different sections you'll see the snakes writhing and squirming.
There are a few of these sorts of optical illusions on the web – a simple image of two people embracing throws your brain into confusion where the couple are at strange angles and it's hard to immediately decipher which head (or other body part) belongs to which person.
Owl Eyes in coffee
Here Stuart Rutherford managed to magic an owl's face inside his coffee mug by simply dropping a couple of Hula Hoops into the mix.
Magic Eye Shark
In the 1990's, Magic Eye was an extremely popular series of books which allowed people to see 3D images by focussing on an otherwise 2D image – usually in the form of a non-descriptive pattern.
Last year Blake Lively posted an image to her Instagram account showing a Magic Eye-like image to help promote her shark movie "The Shallows".
If you're struggling, the official Magic Eye website has instructions on how to view the 3D images but basically you're trying to focus through the image while looking at it (or blurring your vision until it becomes clear).
Common Sense Crossing
Erik Johansson is a Swedish photographer and a whizz with Photoshop who likes to take real photographs and turn them into surreal optical illusions.
Common sense crossing is just one of his many works and one that we find particularly messes with our eyes!
This is a Munker illusion, the combination of colours confusing your brain and tricking your eye to see something you know can't be right.
These tennis balls appear to be different colours - pink, green, white and yellow. They're actually all the same colour, but the addition of the coloured dots confuses your brain into seeing other colours.
A simple photo of a mountainside that shows a man's head apparently cast across the snow. A shadow creating a brilliant illusion that we love.
Pigeons looking for their car
Sometimes optical illusions are just the result of an interesting perspective. This image was taken showing two pigeons perching on the edge of a ledge of a building, but it ends up looking like two massive birds looking to see where they parked their car
Glasses that have eyes
This simple illusion is created by having a reflection of a nearby lamp showing in the lenses of a pair of spectacles. The resulting photo seems to show eyeballs staring back at the viewer from the glass.
The broken bike
This image of a bike sitting with its wheel in a puddle really wreaks havoc on the brain. The reflection appears to show a perfectly formed wheel, while the actual wheel seems bent and contorted in unpleasant ways. Which is the reality?
You would be forgiven for thinking this image is just a really bad Photoshopping, but it isn't. As one Redditor suggested, it's likely the result of a Fata Morgana mirage.
A visual illusion caused by rays of light being bent as they pass through different temperature plains. The difference in air temperature acts as a lens - refracting light and distorting images as we see them.
Hyper realistic drawings
This talent for creating optical illusions is demonstrated in his Youtube video which shows him cutting, bashing and setting fire to the real versions of his creations.
Papa John's Pizza man
Every now and then advertising companies do something clever that captures our imagination. Something as simple an optical illusion can be enough to help a brand stick in our minds.
This advert from Papa John's pizza was deemed clever enough to win an award at the Cannes International Advertising Awards and simply featured a mini pizza delivery man on a bit of card that could be put on someone's front door so when they looked through the viewing hole they saw the man on the other side.
Making the impossible seem plausible
In another advertising campaign, Honda produced a video featuring a range of optical illusions to help sell their new CR-V – all aimed at helping to promote a big car experience but with a smaller economy vehicle.
Stefan Pabst is yet another talented artist with the ability to create optical illusions from drawings, paintings and sketches. In a series of works he creates the illusion of three-dimensional images on flat paper surfaces.
Warning, contains spiders.
The spinning spiral
Another classic deception. This image is not animated, it's just a simple JPG, but if you're reading this text then you're probably seeing it spin out of the periphery of your vision.
The flying weightlifter
Lesman Paredes was pretty happy with his performance at the Junior Weightlifting Championships in 2015 so much so that after completing a 230kg clean and jerk he can be seen taking off from the ground.
Alas, this is not the case of Superman finally revealing himself to the world, but simply a combination of bouncy surface underfoot, heavy weights being dropped after a successful lift and a well-timed super celebratory jump. Unsurprisingly, the photo was later subjected to a Reddit photoshop battle.
You can see it all in action in this video.
Black and white photo
This is a black and white image with the addition of some coloured lines on it. Your brain interprets those lines to see a different reality.
Sometimes it's simply timing, angle and pose that creates an optical illusion. Here this sailor appears to be getting a shoulder run from the sun that's behind him simply because it lines up nicely with his epaulettes.
This only looks normal upside down
This photo of Elon Musk seems normal enough, apart from being the wrong way up. The thing is if you try to look at it the right way around you'll soon find it's not right at all.
This leaf looks like it belongs in Minecraft rather than the real world. Yet here is, existing with its odd-looking multi-coloured finish.
This one looks like one of those photos of bogus bodge jobs that cowboy builders have made. A TV screen seems to be embedded in a wall. Very odd.
We're not sure what's going on here, but it looks like the roof of this truck is floating above the ground and casting a shadow on the stones below as well. How?
At first glance, there's nothing off with this photo. But then when you spy the construction of the pillars and the straight lines through the middle your eyes might struggle to take in the view.
What's going on with the floor?
This massive ancient building sure is impressive, but what is happening with the floor? It's really playing havoc with our eyes.
Half empty or half missing?
This chap sat down at school with a drink cup that looks especially weird on the desk. Where's the rest of it?
Well, there's a hole in the desk and the fluid inside is just the right height to block the rim, resulting in a curious optical illusion.
Paper thin building
It seems that from certain angles some buildings look like they are made of nothing and are defying all laws of gravity and psychics.
This automotive mishap has left a car's front bumper behind. But somehow it looks like the car is mostly invisible or somehow breaking through from another dimension.
Another photo that looks like something that belongs in Minecraft instead of the real world. Just a dog peering through a window.
A chandelier in the sky?
Is that a chandelier in the sky or a particularly interesting UFO like none you've ever seen (or not seen) before?
No, it's just an optical illusion likely caused by reflections but a cool one nonetheless.
Time falling away
This one looks like something has gone wrong with time. The hours and minutes are just slipping away.
But no, it's just a broken watch.