# Illusion of Two Tracks

By on October 10, 2010, with 103 Comments

Here’s a relatively new optical illusion, examples of which were featured on multiple occasions. I think today’s version beats them all! In short, it makes your brain/eyes play a trick on you, making you “feel” that the photo on the right is slightly slanted. In reality it’s not. How can it be that the both photos are exactly the same? Anyone understands what makes this effect work? I have no idea, I tell you, no idea!

• Rob

Wow. My guess is that the illusion is based on the positioning of the horizon and the tracks, combined with the middle of the two photo’s when put next to each other. One the picture the horizon is almost out of sight, in the top left corner. But when you add the same picture on the right, suddenly the horizon comes in to view when you look in the middle. This may trick you in to thinking that the horizon is dead ahead, while the tracks on the left go seemingly skewed. This then leaves a distorted perception of the tracks on the left more than on the tracks on the right. But I can’t speak in any academic terms to explain this. But I would dare to make the assumption that if the pictures would be horizontally mirrored it would be the left picture that would seem ‘slightly slanted’.

• Happy

Oh yeah! I agree with you, it does seem that way! Good explanation.

• Jamie

It’s the lines from the sidewalk on the left and the lines in the grass that seem to me, to make it look slanted

• Ellen Slovac

After looking at this, and studying it I finally lurred my brain into seeing them both slanted. It worked.

• egdirbr

I think it has to do with the perspective and vanishing point, which is the point on the horizon where lines seem to converge. Since the images are next to each other, our eyes want to see them from one perspective point. We look left to right and the vertical line of the border of the grass is far to the side and tells us what is straight ahead. The line that is “straight ahead” on the right image seems like it should veer to the left at a sharper angle based on the perspective point established by the left image.

• Dude

I think it works, because the individual rail on the right is closer to horizontal than the rail on the left. Your brain compares the two rails in the middle and it looks like the one on the left is closer to horizontal than the one on the right.

• toby

wow. impressive. i too overlayed it and all i can surmise is that their position next to one another is the illusion.

• Jess

From far away, it looks the same if you stare at the right one for a while then look at both of them…but it messed with my brain up close.

• Unknown Hacerk

when two line drawings with identical vanishing points of perspective the natural tendency is to view left to right leaving the last image of the line at a more horizontal position next to the next picture which has the first line near prependicular position confusing the balace of sight to beleive the one picture is twisted,

similar to old steroscope pictures.

• Bryan

There are lots of things gong on here, firstly in each picture you have actual parallel lines which appear to converge at the VP (as the brain expects) then because the pictures are side by side all the lines have an actual parallel that really is parallel…. but because the brain expect parallels to converge then it interprets the true parallels in such pictures as divergent.
Yo can play a lot with these pictures by adjusting your focus, see what happens when you focus on eitehr of the VP or the leftmost rains in each picture.

I suspect that what makes these images particularly strong is the way the leftmost path is framed to show as a strong parallel to the edge of the picture frame , if you focus on the paths then you get a strong impression of the picture not being rectangular.

• Lee

if you use the magic eye technique you can see that they are identical.

• Curtis Lindblom

o shit i overlapped them in photoshop and there exactly the same -_- no clue how it works

• Fay

I think the photo’s are taken at diffrent angles one from above the other from crouching down getting the illusion they are different pics

• hiya

to compare the two pictures you’re eyes travel from the slanted lines in the left picture to the relatively straight sidewalk of the right picture. The slants throw off your brain

• Raicuparta

It’s the prespective. The picture on the right has those oblique lines, and in the middle there is a straight line. The brain then assumes that the other picture has the same prespective, so it thinks that the image is not like that. Like if the brain was expecting for the picture on the left to be flipped horizontally, so that the prespectives would match.

I just totally made that up.

• Ajidicia

yes, i think that one of the two pictures “takes the lead”, and set the perspective. The other picture is then seen in this referential and its perspective is added to the lead picture, causing this bent perception.

• Valerie

It sounds totally credible though.

• Moe

LAWLLLL

• Lars Peter Larsen

Instead of comparing track one with track one, and two with two, we are comparing the lines near to each other like a mirror. It`s a bite like Jastrow´s illusion.

• Infantryman154

the pictures are not the same. if you notice, the woman walking on the left side of the picture with her husband. the left picture doesnt show as much of the husband as the right picture. so the left picture is cut out just a hair, but enough, to throw your brain off.

• ohmygosh

I dont get this. it just looks like two pictures of the same place taken at different angles. Where’s the illusion? And whats all this ‘your brain is making you think that the right one is slanted’

AND I dont get what all this prespective and horizon and BLAH BLAH BLAH stuff is about. Can’t people just explain things in plain engilsh way? Can’t you not put all the tech and scientific words in? ok, horizon might not be a scientific word, but the paragraph its in is SO confusing!!! AAARRRRGH I do not get this at all!!!! BLARGHH B DFJGLKK GAH GHAH.

help. i am so frustrated someone please explain in an easy was P-L-E-A-S-E

• ohmygosh

OH GOD

now i get it!!! those are the exact same photos….

I AM SO DUMB.

that illusion is freaky!!

• ohmygosh

I think I now know how it works.

The photo is done twice and put next to each other with a real tiny gap in the middle. Because of this, when you look in the middle, you see the not-so-steep right side of the track in the left photo. The angle of the camera makes that side look not-so-steep because its far away. Then you see the left side of the track in the right photo. Because of the angle of the camera, this line is like coming towards you, so it looks steeper.

Your brain then starts comparing the two photos, and because of what I just explained above, it starts thinking that the right photo’s track is steeper.

I think its all about the angle of the camera and the placement of the photos. If the angle wasn’t like this the sides of the track would be different sizes and lengths, and if you put the photos not-so-close together obviously they would look the same.

I CAN’T BELIEVE I DIDN’T PICK UP THE ILLUSION AT FIRST

• Claire

I think it’s because the brain works out the angle by comparing it to another straight line close by, so on the second or right one, the track angle is based on the slanted lines beside them on the left.

• Rhelyc

Umm…they look identical to me…

• Wim

I think it’s on which picture you’re focussing. If you focus on one picture, the other one appears slanted. If you then focus on the other one, the first one seems slanted now. Fun effect :-)

• Dave

If you look at the couple to the left of the tracks you can see that the camera angle is skewed to the left, just a touch, so you can see more of the couple in the picture on the right.

• Bert

They are exactly the same. The brain thinks that the right one is part of the left one, therefore it would only be natural to have the perspective lines end at the same point in the horizon as on the left. However, since the end-point is moved to the right, the brain concludes that the right picture must have been rotated clockwise.

• Le

The picture on the right is moved slightly to the left. You notice it with the couple top left.

So Far I have read good guesses as to why this is happening however both the response so far though on the right track are wrong. the reason the tracks on the right seem to be straighter than the ones on the left have nothing to do with the horizon nor the straight line between the photos. it is because of the positioning on the tracks them selves. The way the tracks start one coming from the bottom one from the right hand side of each individual picture causes the tracks on the left to make your brain interpret the set on the right as being straighter. To see this reaction in detail simply take a piece of paper and cover the bottom 1/4 of the pictures and compare it. Then slowly move the paper up. as less of the tracks become visible the pictures begin to appear more and more identical. Meanwhile both the horizon and the straight line between them are both still clearly visible. Again to both the previous posters very good guesses.

• patko0770

i dont see any difference

well they aren’t “exactly” the same. there is a small difference in the start point, so to speak. in to one on the right you can actually see more of the person wearing the brownish jacket.
there is a 1-2 degrees difference between them.
this is used to create a 3D effect when looking at the 2 images and crossing your eyes.
if you try to overlap the images you’ll get a third one in the middle that’ll seem 3D

same as technique as the one with the “toast and eggs” illusion. (sorry for the second post. i just remembered the illusion posted not too long ago)

• mohamed rootshell

easy illusion

the picture in the right was token from adistance before the distance of the left picture, and was typically accepted and was token exactly as the left, that’s why the appeat as it was slanted

i don’t think these two pics are the same ones. if you look at the man’s right leg on the left picture, you’ll see it’s more cut off than the right picture.
as well, the man sitting on the chair in the upper right corner changes as well – just barely though – the chair isn’t covering the dark line running up the wall on the right like it is, slightly, on the left.
and finally, the lines in the sidewalk bisect with the edge of the photo graph higher up on the right one than the left one.
i’m thinking that the guy took the first pic and then adjusted his camera by turning it a few degrees or moving it onto the grass an inch or two then did a little cropping.
but i could be wrong…

• Sheila

The right one appears a shade lighter than the left. focus on the grass. also the carriage on the right side of the track is slightly blurred.

• Nahum

Actually, it’s eyes issue – they try to focus on different pictures, and your eye tries to make an 3D pic out of it – it’s close enough for it.

Try spacing the pictures, and the illusion will disappear.

• Jimbogoodski

One other interesting effect that I noticed. If you get very close directly in front of each picture, as you approach the one on the right, the left picture seems to slant even further. When you approach the picture on the left the right picture almost seems to turn straight! Anybody else see this? Maybe my eyes are more like Marty Feldman’s…. (Igor from Young Frankenstein!)

• Katherine Kirk

There is a slight difference in the pictures. I don’t know if it’s a difference in lens used or of angle. Check out the people in the upper left corner.

• KYBonz

I think it has to do with the sidewalk at the left of both pics. Even though the photos are identical, the “frame” isn’t. The sidewalk in the right photo has the dark green grass on both sides, drawing your eye to it and making it appear (to me) to be wider than the same sidewalk in the photo on the left.

• Qbee37

Pretty cool. Cut the picture in two, reversed the two halves and got identical results. the only trickery is clearly in the brain.

• James

Try making a 3 photo panorama and it gets even weirder. The left stays the same, the middle one seems slightly skewed but the right looks way off. Crazy!

in fact they are not exactly alike, eh noticed that the picture on the right people who are walking on the left, are more spacious and bigger than the width of the photo on the left.

is a fraud

• I believe Rob and Raicuparta both have it correct (made up or not). The two pictures together give the viewer a center; which is the top left corner of the picture on the right, only the brain actually sees two horizons and immediately chooses the center of the picture which throws the picture on the left off kilter. (Just my opinion.)

• David

Maybe you made that up, that sounds like a perfectly reasonable explanation. Perspective tricks are always a bit wonky that way.

I think you hit the nail on the head pointing out that straight path up the left-hand side of both images. More to the point, the guy in the red shirt and white pants. Positioned as he is, he hides the vanishing point of that left-hand pathway – and thus takes the perspective out of that path.

That throws the perception of everything else off. I bet if you photochop out that left-hand path, and put both pictures side-by-side, they’ll look exactly the same. The illusion is the *path*, not the tracks.

• Susan

Your eyes/mind want the tracks to be parallel when the photos are side by side. But because there is such a long-distance perspective, they can’t be, just like the two tracks in the single photo are not parallel. (If you look at the same track in each photo as two sides of a road your eyes/mind can process the perspective better, though it is in reverse with the tracks getting wider closer to you.)

• Camika

I wonder if the effect is cummulative… If you place another copy of the photo on the rigth side will the tracks on the leftmost picture appear even more slanted?

• Pete

i believe that the picture on the right is just squashed horizontaly so the picture seems to be at a diiferent angle otherwise no idea!!

• Sj x

This is definately the best one of these types of illusion I have seen!
I know how it works but i can’t explain it LOL
very good illusion :)

• Fred

It does not look like the same photo but indeed it is. It appears that while observing the lines on one, the mind expects the other to converge at the same focus.
It’s hard to see it for what it really is. The same picture side by side. Very intriguing.

• Chris

huh? i don’t get this. can someone xplain this 2 me?

• dave moore

If in looking logically at the illusion, you compare the left side of each converging track followed by comparing the right side of each, it’s easy to see that they are parallel. But unaided by this rationalizing maneuver, I simply look in an uncritical way, I default into comparing the “medial” sides of each track and the illusion is created by my brain. I would be interested in seeing the two identical pictures placed above one another to test my presumption.

• Herman

It is clearly not the Horizon. If you hide the top of the picture (The horizon) the effect is still the same.
I believe that we are focussed to the center of the picture (in thise case of both pictures). There you see a few vertical line’s (the rail, the green and the road). The lines on the left are clearly not vertical. The next step is realizing that you see twice the same picture. And since that is so unbelievable you think the left picture is slanted.

• ntlgnce

Both pics are the sxact same. I believe its called the rainbow effect or something,, You know the “Which one is bigger” the top arch or the bottom? The first photo causes your eye to shift, giving the appearance the second photo is different. Save the picture to your computer, then right click and open with, “paint” lable one A the other B, and split them apart, and flip flop them.. ( I would have added a pic, but the website is lame and cant just use the microsoft uploader…)

• Ken

Both images are exactly the same.

Using the contrast of the grass and the pavement, both images side by side create more lines that confuse your brain.

You notice the straight edge of the grass-line on the right image more, and the angled lines of the tracks on the left image more.

• Hm, this is a good one.I think(and beliveme I”m not sure at all) the sidewalk with the two figures walking appears to be very slightly smaller. There is a little difference with the left figure, if you look very closely there is a little less leg showing.

• Chris

I definitely agree. A slight difference can make everything, well, different.

• Marco Garcia

I think it has to do with your dominant eye if your left handed the one on the right looks slanted i’m right handed so the left one looks slanted to me, i’m not sure I thinks thats why its different for everybody

• steven

it has to do with your mind playing tricks on you, the mind sees the image on the left as slanted and therefore your mind thinks the next one over should comply with the laws of perspective making you feel like its a straighter track when in fact its exactly the same pic.

• Ken J

Sad to say.. the one on the left looks slanted to me..
Of course it would…lol

• It’s just the way our brain reads it. Since the tracks in the picture on the left appear to run under the picture on the right, which is the point we focus on, the the eye then follows the tracks in the picture on the right up to the top. This appearance of a ‘V’ makes us believe that the tracks are from a different point of view.

• I like Raicuparta explanation and I’m always puzzled about “slanted lines” illusions!

I tried to see these 2 pics in stereoscopy by crossing the eyes and… yes… I’m pretty sure they merge into a 3D picture: the tracks end in distance and the figures stand out.
This is just a curious observation. This does NOT explain the “slanted” illusion described above.

• David

Each line is actually parallel to the corresponding line in the other photo. As they get farther away from the viewer they should therefore converge, but they don’t, so the brain thinks the tracks are getting farther apart as they recede into the distance?

• Digit

This seems to be “illusional” because we have BI-FOCAL vision. So, with the horizon being in the top left, our left eye sees the “correct” version, however, the right eye will not perceive it the same because it has to “look” left to see the horizon. This will naturally distort the way the right sees the 2 images. Obviously, the same would happen if the pictures were flipped around. Then the right will see the “true” version and the left will see the distorted version. If the horizon was in the middle, ones brain would not see the distortion.

• terry the censor

I have been disappointed in many of the illusions posted since I subscribed but this one is both simple and excellent. Thanks!

• maria

its the possision of the photo .

• Hjaldemar Morales

Cross your eyes and make one picture out of it. It’s Cross eye 3D image without classes ;-).

• Jian

The Illusion happens because when we ssee 1 of the photos we slighly turn our heads to match the photo’s inclination, so the other looks slanted

• No one

The two pictures are not identical. So the pictures are at slightly different angles.

• Dave

On the wall in our kid’s room we had a border that had a city block – the idea was to play with re-usable stickers. There were about four buildings, a street in front of the buildings, and then a street crossing that one which would go off into the distance. It was blocked by the buildings mostly, but went ‘into’ the picture at about 30 degrees. Since it was just a repeating roll of wall-paper – my mind ***KNEW*** that the street going into the picture was always the same angle. But I could never convince my eyes.

• seth

this illusion is actually because of the angle of both of the pictures. yes, it is true they are the exact same picture but the perspective creates a triangle shape for one of the tracks in our mind. though the sides are paralell to eachother in each of the individual tracks, the perspective makes them slanted to eachother looking like diferrent slants. when the one side of the track that should be parallel is matched p with the other side, it makes it look more slanted because our mind is theorteically saying “hey wait a minute”…….at least i think. i hope that makes sense.i seem to have overcomplicated my explanation.

• Mark

I agree with Maria… Looking at the two photos, the photographer repositioned between shots…It’s actually very easy to pick out. Look at the bottom left to bottom middle of both photos. The photographer is closer to the center of both reference points in the photo on the right.

• Fred

The two pictures are identical. Superimposing a transparent mask of one over the other makes it clear.

• Sagamore

It is all in a matter of perspective. Like Neil deGrasse Tyson says on certain days when looking at the moon its a matter of our perspective. So, to correct that one would look at the object, or these 2 photos with head upside down. Perspective is rendered irrelevant then. Thank you.

• Care Bear

I’m suffering from double-vision right now so this is totally confusing.

• Ben

If you click on one of the pictures and it opens up in a new window, cover one picture with your hand and alternate closing each eye. It makes the track slant and then straighten.

• Paul Ferrar

The photos are not identical, The one on the left when looking at the sidewalk there is a line going parallel and when you look at the second picture it is there only you see it sooner in the photo. Also in the first photo one of the people is cut off. Likely as mentioned by others before me two pics taken very quickly with a slight move in the positioning of the camera. Neat photos though. :)

• Waygood

I agree with Ken J, saying the left image is slanting, as I am left eye dominant. I suspect he is too :)

• Dieu

Stop saying the two image are different… its only a pixel. The illusion is created by the point of horizon… In drawing you learn that when you make things converge into two different point of horizon this make them seem like not parallel… your eyes do a picture of the whole things instead of each seperately. It’s not the little space that have been removed when puting the picture next to each other.

• Daron

Seems to me that the reason they don’t appear to be aligned the same is that when they are this close together, your brain is expecting the lines to meet far off at the same vanishing point. Since they are not lined up with the vanishing point then your brain assumes they must not be parallel.

• jimmy joe

its just stretched out…

• Anamaria

Guys, there is no difference. Its the same photo, it is just that your brain is playing tricks on you, but if you look closely and compare them(use a ruler on your monitor) you will see they are the same.

• John Glynn

Here’s how I think it works, you have the same picture side by side, the side walks are going in the same direction in they’re respective frames, since one is off to the left, it looks as though it’s turning left in comparison to where the other one ends. Sorry if I ruin it for anyone.

• Suji

Those are how our left eye and right eye see an object individually.
The left photo is how our left eye see and the right photo is how right eye see.
To test this, take a box (it can be any; but should be straight corners and straight planes and should be bigger than upper eye level, when you sit on a chair and place the box on the table) and sit infront of one corner with a distance, now see the box with both eyes. And then, see with one eye closed, but do not move or tilt your head. you will get 3 different images. If depth appears, then long side disappear and if long side appers then the depth disappears. And with both eyes, you can see clear image of box.
If one does not have both eyes open, then that person easily mis-judge everything in depth mostly.
Here, we are now trying to compare those images individually. However, when our both eyes give those image to our brain, and our brain interpret as one and gives us a more informations like depth of field, and of course a 3D image.
To see the 3D image with these two photos, try to see farther in the computer screen, then those images split apart, and keep those images to move until right eye’s left image and left eye’s right image overlap each other.- If our head slightly tilted then those will not overlap- then we can see another beautiful image.
These photographs can be taken by attaching two small point and shoot cameras bottoms together, and take one shot, but both cameras should click simultaneously. And then place those photos side by side as viewed here, and then should see the 3D image as I described earlier…

• Grey

isn’t it just stretched?

• ilkay

i think i got it. the two pictures are identical but the reason we se it different is because of the surroundings of the pictures.To the left of the first picture we only see the border of the site etc but to the left of the second picture we see the the grass on the first picture which is not vertical and that is what causes this illusion.

• BrainStorm_wf

First: Second looks a little slightly because the lines in the picture are not parallel, that make the eye to think they have a little rotation.

But anyway I’m agreed that the pictures aren’t exactly the same. If you see the man of red shirt, at his right side, the 2nd picture is a little bigger.

• Lakis

To my modest opinion this happens because the brain cannot accept to deferent perspectives in one image (it could think like Picasso in that case).
In one image there is one point of view so the two pictures, who belong in one image for the mind, they must have one perspective. Lower down corner serves as point of reference for the mind and calculates the angle of each individual vanishing point in a different angle from it. For that assumes that they are differently tilted. (see image 0 and 1).

If we add a third picture, it looks more tilted for the same reason. (see image 2 and 3).

In the quadruple example, the two pictures in diagonal look the same tilted, as their vanishing points are in the same angle from the corner. (see image 4 and 5).

This is my explanation. A scientist can reword it better.

• ronnie

its because they are side by side if you put one on top the other you can see they are exaactly the same. but it is very cool.

• ferret

Hey does it cost money to make a avatar?

• Hello

The two pictures are exactly same….I cut the 2 pic on photoshop and pasted the picture on first pic…and then set the second picture as Overlayed…Its matches…

• thing

Steroscopics picts… period.

a big lol for all the “scientifics” explanations…

• Lasse

Well they’re really not the same size, try to copy both – Left pic is 292×220 while the right one is 294×220…

• Dude

the snwy part on the right pic looks like the wite background, so you dont notice it

• steph

it looks like an illusion because the straigthness of the sidewalk on the left throws off your focus to the correct and same angle of the two photos making the angle look sharper, it is merely a trick of the eye.

• Michael

I held up two straight edges, one to the left track in the left pic and one to the right track in the left pic; they are not parallel. But the left track in the left pic is parallel to the left track in the right pic and the right track in the left pic is parallel to the right track in the right pic.

But there is a difference between the two pics though it is very subtle. If you measure the distance from the left edge of the left pic to the left hand grass line you will find it is a bit less than the measured distance from the left edge of the right pic to the left edge of the grass line. The two pics were taken from two very distinct viewpoints.

• just look at the right down cornet…..it’s make a different causes an angle….right?

• Plmko

It is because you brain thinks it is one picture with the middle between the two pictures, not two same pictures.

• Amber Rosalie

It’s simply because the straight edge of the right photo is right beside the angled line of the grass in the left photo. The photos are identical, but because the lines in the images aren’t parallel, it throws you off when looking at the adjacent lines of the grass on the inner sides of the photos..

• JohnR

It looks slanted because the straight edge on the right picture, is next to the diagnol edge on the left picture, therefore it makes your mind think that the picture is actually tilted. because is this was reposted, with one on top of the other, rather than next to it, they would look EXACTLY the same :) hope this explains it…

• Since both the images are same, our brain is looking at them from a single perspective. Since the left most edge of the left image serves as the fist angle running towards its infinity(note: in our mind the vanishing point is supposed to be same for both the images since both are being looked from the same perspective) the middle edge of the image(which actually is the first edge of the right image but is still serving as continuation of the same perspective) seems to be suddenly diverted away to a new vanishing point and so appears to be rotated clockwise.

• Rhi

At first looking, the pic on the left (to me) looks slanted. I am however myopic haha Dunno if that makes any difference

• Q Being

These can be viewed as a stereoscopic image. Just like the “Magic Eye” Pictures” If you unfocus you eyes and allow them to cross you can see a third middle image in 3D