# Can we calculate the optical illusion?

1. Oct 22, 2008

### janakiraman

Hi I was just wondering if it is possible to calculate the optical illusion. For example consider a barrier for the car park. It looks very long when it is vertical and upright but very small when it is horizontal. The illusion that we obtain when the barrier is vertical will make us assume that if the barrier is horizontal to be much longer than the actual length. now my question is, is it possible to calculate the difference between the illusion length and the actual length by the principle of optics? If so how

2. Oct 22, 2008

### HallsofIvy

I have no idea what "optical illusion" you are talking about. I don't know why you think being "horizontal" or "vertical" would affect how large something looks. Are you possibly talking about the difference between look down the length of an object as opposed to looking at it at a right angle to its length?

3. Oct 22, 2008

### Manchot

Optical illusions are primarily mental effects. There was a neurological paper published a few months ago about how the brain is constantly extrapolating what you see into the future, and they speculated that illusions were a result of the extrapolation gone awry.

4. Oct 22, 2008

### Naty1

But there are also optical illusions that can be recorded on camera, not brain constructs, such as those caused by temperature inversions in deserts....of horizon distortions on water where trees appear to "float"...

Likely these are caused by light scattering in different ways from different density air and hence displaced from their "normal" locations....

5. Oct 22, 2008

### janakiraman

@ HallsofIvy

No the illusion i'm talking about is when you see an object like a carpark barrier upright the mind always extrapolates its length and if we are ask to calculate the distance mentally how much it would be in horizontally we always end up calculating more than the actual distance when it is horizontal. I just wanted to know if by principle of optics we can calculate this illusionary extra distance that our brain calculates.

6. Jun 16, 2009

### janakiraman

@ Naty1

That' s very close what i had tried to frame. Maybe a better way to ask is what causes such illusions in a camera? And by the way your answer was very abstract. Can you please explain in detail about the same

7. Jun 16, 2009

### ZapperZ

Staff Emeritus
But are these REALLY considered as optical illusion? They are not illusion because they are due to basic optics.

I tend to think that optical illusion is more of what Manchot has described, which makes the topic of this thread very puzzling.

Zz.