The Cellar  

Go Back   The Cellar > Images > Image of the Day

Image of the Day Images that will blow your mind - every day. [Blog] [RSS] [XML]

Reply
 
Thread Tools Rate Thread Display Modes
Old 12-18-2007, 08:52 AM   #1
xoxoxoBruce
The future is unwritten
 
Join Date: Oct 2002
Posts: 71,105
December 18, 2007: Illusion



2007 First prize.
Quote:
Here is a novel illusion that is as striking as it is simple.
The two images of the Leaning Tower of Pisa are identical, yet one has the impression that the tower on the right leans more, as if photographed from a different angle.
The reason for this is because the visual system treats the two images as if part of a single scene.

Normally, if two adjacent towers rise at the same angle, their image outlines converge as they recede from view due to perspective, and this is taken into account by the visual system. So when confronted with two towers whose corresponding outlines are parallel, the visual system assumes they must be diverging as they rise from view, and this is what we see.

The illusion is not restricted to towers photographed from below, but works well with other scenes, such as railway tracks receding into the distance. What this illusion reveals is less to do with perspective, but how the visual system tends to treat two side-by-side images as if part of the same scene.

However hard we try to think of the two photographs of the Leaning Tower as separate, albeit identical images of the same object, our visual system regards them as the ‘Twin Towers of Pisa’, whose perspective can only be interpreted in terms of one tower leaning more than the other.
__________________
The descent of man ~ Nixon, Friedman, Reagan, Trump.
xoxoxoBruce is offline   Reply With Quote
Old 12-18-2007, 08:53 AM   #2
Shawnee123
Why, you're a regular Alfred E Einstein, ain't ya?
 
Join Date: Jun 2006
Posts: 21,206
OK, I think my brain just blew up. That is amazing!
Shawnee123 is offline   Reply With Quote
Old 12-18-2007, 09:07 AM   #3
ZenGum
Doctor Wtf
 
Join Date: Oct 2007
Location: Badelaide, Baustralia
Posts: 12,861
Nah, that's gotta be trimmed or very subtly 'shopped ....

[gets ruler, measure screen in six points on each picture, finds perfect match]

... holy malarky, I think my brain just got discombobulated!
__________________
Shut up and hug. MoreThanPretty, Nov 5, 2008.
Just because I'm nominally polite, does not make me a pussy. Sundae Girl.
ZenGum is offline   Reply With Quote
Old 12-18-2007, 09:30 AM   #4
Phage0070
Snooty Borg
 
Join Date: Dec 2007
Posts: 81
There actually is a slight trimming; while the top portions of the image are the same the bottom portion has been altered. About where the first series of pillars meets that floor two or three pixels have been removed in a line across the second image. The images are the same size though, so on the second image you can actually see more of the structure at the bottom. The images are also slightly out of line; the second image is several pixels higher than the first image.

Imagine a two parallel slanted lines, then remove a portion from one line and mate the ends vertically, extending the bottom of the line by the same amount. What you end up with is two lines that are still parallel, but the top portion of one is farther over in the direction of the tilt. It is amazing our brains can detect such subtle manipulations, but it is not completely brain-based.
Phage0070 is offline   Reply With Quote
Old 12-18-2007, 09:52 AM   #5
glatt
 
Join Date: Jul 2003
Location: Arlington, VA
Posts: 27,717
Well, this may make it even more confusing. I drew a slanted line and attached the picture twice (under different names.) Do the lines look parallel, or is the one on the right tilted more?
Attached Images
  
glatt is offline   Reply With Quote
Old 12-18-2007, 10:39 AM   #6
LJ
i am myself
 
Join Date: Nov 2007
Location: via blackberry, maybe
Posts: 750
the seperate image thing must matter
Attached Images
 
__________________
Whether I shall turn out to be the hero of my own life, or whether that station will be held by anybody else, these pages must show ...
-C.Dickens
LJ is offline   Reply With Quote
Old 12-18-2007, 10:52 AM   #7
Slothboy
*No known superpowers.
 
Join Date: Apr 2004
Location: Oregon
Posts: 48
Quote:
Originally Posted by Phage0070 View Post
There actually is a slight trimming; while the top portions of the image are the same the bottom portion has been altered. About where the first series of pillars meets that floor two or three pixels have been removed in a line across the second image. The images are the same size though, so on the second image you can actually see more of the structure at the bottom. The images are also slightly out of line; the second image is several pixels higher than the first image.

Imagine a two parallel slanted lines, then remove a portion from one line and mate the ends vertically, extending the bottom of the line by the same amount. What you end up with is two lines that are still parallel, but the top portion of one is farther over in the direction of the tilt. It is amazing our brains can detect such subtle manipulations, but it is not completely brain-based.
Hm. Actually I didn't believe this was unaltered either, because even if I covered one with my hand the other looked like it leaned more. But I opened up the Gimp, cut the image in half and moved one on top of the other with 50% transparency. I also increased the Flash Gordon noise and put some science stuff around. They are exactly the same.
__________________
Super perfundo on the early eve of your day.
Slothboy is offline   Reply With Quote
Old 12-18-2007, 11:30 AM   #8
ogwen69
Custom User Title goes here
 
Join Date: Mar 2007
Posts: 42
Best IOTD ever?

but only cos my brain just exploded.
ogwen69 is offline   Reply With Quote
Old 12-18-2007, 11:37 AM   #9
LJ
i am myself
 
Join Date: Nov 2007
Location: via blackberry, maybe
Posts: 750
The perspective matters, too....and i think the colors do a little bit to them as well.
Attached Images
 
__________________
Whether I shall turn out to be the hero of my own life, or whether that station will be held by anybody else, these pages must show ...
-C.Dickens
LJ is offline   Reply With Quote
Old 12-18-2007, 11:39 AM   #10
classicman
barely disguised asshole, keeper of all that is holy.
 
Join Date: Nov 2007
Posts: 23,401
Damn LJ your whole image looks tilted to the left now!
__________________
"like strapping a pillow on a bull in a china shop" Bullitt
classicman is offline   Reply With Quote
Old 12-18-2007, 11:44 AM   #11
lookout123
changed his status to single
 
Join Date: Apr 2004
Location: Right behind you. No, the other side.
Posts: 10,308
does the image change if you put the whole thing on a treadmill, though?
__________________
Getting knocked down is no sin, it's not getting back up that's the sin
lookout123 is offline   Reply With Quote
Old 12-18-2007, 11:46 AM   #12
classicman
barely disguised asshole, keeper of all that is holy.
 
Join Date: Nov 2007
Posts: 23,401
The coloring of the sky looks darker to me. I have to get off this thread, my brain hurts. Think I'll go post in Ducks headache thread.
__________________
"like strapping a pillow on a bull in a china shop" Bullitt
classicman is offline   Reply With Quote
Old 12-18-2007, 11:50 AM   #13
Shawnee123
Why, you're a regular Alfred E Einstein, ain't ya?
 
Join Date: Jun 2006
Posts: 21,206
Quote:
Originally Posted by lookout123 View Post
does the image change if you put the whole thing on a treadmill, though?
I don't know, let me ask upper management. Is that a problem?
Shawnee123 is offline   Reply With Quote
Old 12-18-2007, 11:53 AM   #14
AndyDan
Soli Deo Gloria!
 
Join Date: Aug 2007
Posts: 7
Seems to me the true test would be to reverse the two original images and see if you still get the same effect.
__________________
The generation of random numbers is too important to be left to chance.
AndyDan is offline   Reply With Quote
Old 12-18-2007, 12:17 PM   #15
Phage0070
Snooty Borg
 
Join Date: Dec 2007
Posts: 81
As I said, the shifting is very subtle and it would be difficult to see it simply by overlaying a semi-transparent image over the other. A better way is to overlay the image using the "Difference" layer quality; this method of overlay means that pixels nearly identical between the two images are made dark, while increasingly dissimilar pixels are lighter in color.

The image was compressed when it was put online, and many compression methods will leave artifacts around the edges of sharp color transitions. What would be expected from an identical image overlayed with the same compression method would be a very faint outline of sharp color transitions over an almost completely black image.

Instead we can see a sharp transition between mostly black to bright outlines, indicating the images do not match up along these transitions (where the differences are more dramatic). If the entire image was this way it would indicate the overlay was out of alignment; the fact that only sections of the image do not match suggests tampering. Once you know where to look you can see the change by alternating full opacity layers.

The first image is with the overlay matched to the bottom section. The second image has the overlay shifted down to align with the upper section. The second image shows a suggestion of another cutting about 1/3 of the way from the top, look for the horizontal bright pixels.

.
Phage0070 is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT -5. The time now is 12:40 PM.


Powered by: vBulletin Version 3.8.1
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.