Optical illusion bewildering the internet

[seeder]

The train track optical illusion that's bewildering the internet

This video - of a father shuffling around his son's toy train tracks - has bewildered the internet. Can you figure out what's causing the optical illusion?

It was posted on Twitter by BBC trainer Marc Blank-Settle on Wednesday evening, and been shared thousands of times since then.

The track on the bottom appears to be much longer than the one on the top, but when one is placed on top of the other, its clear that they are in fact the same size.

Many viewers were left completely dumbfounded.

http://www.bbc.co.uk/news/blogs-trending-35989211

[EllJay]

Jastrow Illusion

This is a classical “geometric illusion”, a variation on the version first described by Joseph Jastrow in 1891 . A number of studies have examined it, still this illusion is not well understood. Jastrow himself wrote (I edited his words so they make sense without his context, and they apply to his figure depicted below on the right): “The lower figure seems distinctly the larger, because its long side is brought into contrast with the shorter side of the other figure. … In judging areas we cannot avoid taking into account the lengths of the lines by which the areas are limited, and a contrast in the lengths of these is carried over to the comparision oft the areas. We judge relatively even when we most desire to judge absolutely.”

[Redefining Success]

The same thing happens with 2 car wheels, noticed it when I was an apprentice at Audi.

[Habitat]

This illusion certainly bewilders me, hard to credit squares A and B are the same shade:

[ChrLzs]

Sorry, but this is the WORST demonstration of an optical illusion I've ever seen. The vast majority of the 'effect' here is very simply that the lower one is significantly closer to the dam camera!!! It's just simple lens foreshortening effects that cause this - in the actual picture of the two items the lower one IS MUCH LONGER and there's no illusion causing that. Grr.

While the other illusory effect is real, this example of it is using another effect altogether to make a mountain out of a molehill! The reason the lower one seems much bigger is that it is closer to the (wide angle) lens of the (deliberately angled) camera. If it was placed PROPERLY and perpendicularly overhead, the effect would be much, much less.

This really is just plain cheating. Perhaps not deliberate, but I doubt it. Here's an overlay of the two pieces showing the lower one IS much longer in the picture...

All I did was crudely cut the top track out, darkened it a bit to make it clear, then dragged it down with no resizing to show it IS shorter...

Geez, measure it with a ruler...

What you are seeing here is someone who really should know better, screwing up with their knowledge of how camera lenses and simple magnification works. This is just what happens when you use a wide angle lens up close to objects, UNLESS you hold it exactly perpendicular.

I'm sorely tempted to repost that wonderful Father Ted clip... "Small... FAR AWAY!"

[Susanc241]

ChrsLzs - I have been thinking about your solution, but it does strike me that if the perspective is the reason behind the size discrepancy, then on the image the back piece of track is already smaller than the front one due to perspective only. To lift that back one off the image and overlay the front one with it is not a true comparison, as you are not including the increase in size that would occur in real life as it is brought forward those few inches.

My impression of the illusion is that if the two tracks were lined up centrally (I do not have the skills to do an animated example) rather than just at the left hand side, and were photographed from directly overhead, they would be the same size.

[Atuke]

This happens every night if you watch baseball on tv. The batter looks like a midget and the umpire looks ten feet tall. Foreshadowing or some phenomena. Simple optical illusion is all

[Atuke]

Obviously part of the trick is the background or table. The wood grain hides the fact that it is on a major downward slope going the other direction. The track is glued to the table and the piece that lays on top stays secure because of the grooves. Crappy film job and demo, enough to p*** me off

[BishopRyan]

Not sure why people are struggling with this. The cheating accusation is inaccurate yes the bottom piece is closer to the camera so the cut out wouldn't be to scale but its all about how the top piece is aligned...is not just the camera.

The problem is where the guy lines up the track on top. Lets call the top track "A" and the bottom track "B". The bottom of track A should not be aligned with the top of track B. This is why the top of track A is so far left.

In the simplist of terms track A should be centered on top of track B not aligned left. Its really that simple. The outer curve is longer than the inner curve so the optical illusion is created when you take the shorter "bottom" curve and attempt to line it up with the longer "outer" curve of track B...instead of simply centering the shorter bottom curve of track A over the longer top curve of track B.

Edited April 9, 2016 by BishopRyan

[Nnicolette]

Well the lower piece is just sitting slightly to the right... Its not that baffling.

[seeder]

Sorry, but this is the WORST demonstration of an optical illusion I've ever seen. The vast majority of the 'effect' here is very simply that the lower one is significantly closer to the dam camera!!! It's just simple lens foreshortening effects that cause this - in the actual picture of the two items the lower one IS MUCH LONGER and there's no illusion causing that. Grr.

While the other illusory effect is real, this example of it is using another effect altogether to make a mountain out of a molehill! The reason the lower one seems much bigger is that it is closer to the (wide angle) lens of the (deliberately angled) camera. If it was placed PROPERLY and perpendicularly overhead, the effect would be much, much less.

This really is just plain cheating. Perhaps not deliberate, but I doubt it. Here's an overlay of the two pieces showing the lower one IS much longer in the picture...

All I did was crudely cut the top track out, darkened it a bit to make it clear, then dragged it down with no resizing to show it IS shorter...

Geez, measure it with a ruler...

What you are seeing here is someone who really should know better, screwing up with their knowledge of how camera lenses and simple magnification works. This is just what happens when you use a wide angle lens up close to objects, UNLESS you hold it exactly perpendicular.

I'm sorely tempted to repost that wonderful Father Ted clip... "Small... FAR AWAY!"

Although the two tracks are identical, when one of the curved pieces is placed below the other, the lower one appears to be larger.

That’s because the short edge of the upper track is being compared to the long side of the lower one.

Read more: http://metro.co.uk/2016/04/07/this-train-track-optical-illusion-is-making-peoples-heads-hurt-5802109/#ixzz45LPsAYVt

Edited April 9, 2016 by seeder

[danielost]

it is simple the upper curve is longer than the lower curve. put the upper curve against the shorter curve and the whole piece looks smaller.

[pallidin]

This illusion certainly bewilders me, hard to credit squares A and B are the same shade:

Yeah, my roommate never believed it, even after showing that it is true. My favorite illusion also.

[ChrLzs]

ChrsLzs - I have been thinking about your solution, but it does strike me that if the perspective is the reason behind the size discrepancy, then on the image the back piece of track is already smaller than the front one due to perspective only.

Yes. That is precisely WHY I didn't magnify the second piece - that would have been pointless.

To lift that back one off the image and overlay the front one with it is not a true comparison

Of course it isn't, and THAT is the whole point!!!!!! HE's the one who had the camera angled and thus DELIBERATELY ensured the farthest track would be smaller, and it would therefore look bigger as it was brought forward. That magnification effect (which has nothing to do with the Jastrow illusion and in fact is most definitely NOT an illusion) is exactly what I DID NOT include in my demonstration! YES, the Jastrow effect is real. But about 80-90% of the effect in THIS video is simply because of the bad positioning of the camera. Cameras ALWAYS render images down to 2D, thus you can make things larger or smaller simply by using that effect alone. This guy has tangled two things up and used his camera to create a HUGELY greater effect than actually existed from the illusion. From that point of view it is a fraudulent demonstration of the effect - it uses a completely different issue to ridiculously exaggerate it.

If you still don't get it, and think that I should have magnified the thing as I moved it... you are really not getting this at all.

My impression of the illusion is that if the two tracks were lined up centrally (I do not have the skills to do an animated example) rather than just at the left hand side, and were photographed from directly overhead, they would be the same size.

Of course they would, just as he shows when he puts them together... but like I said, the vast majority of the effect here is because of the angled camera. My animation CORRECTLY shows just how much of an effect THAT is.

[Vlawde]

It doesn't take much to bewilder the internet. It can't even decide the color of a dress!

Edited April 9, 2016 by Vlawde

[muzzy101]

It baffles me that this baffles people. Obviously, the arc length does not change by simply moving one of the pieces. It stays constant. The moved piece appears longer because it is moved closer to the unseen (and therefore undefined) center point of the non-moving piece's arc length. Trust me, I'm an engineer.

If you don't believe me, do the math. s = r x θ where s = the length of an arc on a circle in radians, r = radius of the circle, and θ = the angle of the arc length in radians.

Edited April 9, 2016 by muzzy101

[Ashyne]

The left corners aren't even aligned with each other, so of course the bottom one with the corner further to the right will look longer.

[Darkenpath25]

Aw but illusions are so much fun

[kobolds]

pay attention to the hand . you will see the trick

[AZDZ]

I don't see any funny business with the hand. Another example of the illusion in action.

http://www.youtube.com/watch?v=SAzNYQr3aPo&nohtml5=False

If there is some sneakiness going on I cannot discern it.

[danielost]

mussy and I have already explained this.

[pallidin]

In it's standard form, this is an "optical illusion" with 2-d, not a 3-d capable illusion.

[Calibeliever]

This

[Princess Serenity]

Ever since "The Dress" it's been optical illusion after optical illusion. |: I'm getting a little bored of them.

[ChrLzs]

I don't see any funny business with the hand. Another example of the illusion in action.

http://www.youtube.com/watch?v=SAzNYQr3aPo&nohtml5=False

If there is some sneakiness going on I cannot discern it.

? So you, and it appears the vast majority of respondents, cannot see that the camera is in front of the items and tilted upwards? That it is NOT anywhere near overhead, which it would have to be to show a fair rendition of the objects' size?

As I've tried (and clearly failed) to explain, the angle of the camera means the front item is significantly magnified... That pretty much renders the 'illusion' aspect invalid.

Edited April 11, 2016 by ChrLzs