Follow up to - Why do things look smaller just bacause they are further away?

Question

Wow, only now, after four attempts, do I really understand how hard this question is to answer.

Most of your answers have been very informative and I thank you all for enlightening me with the information that you have.

However I feel the question here is the failing and I will attemp to express it differently.

Here goes ..... If I am 6 feet tall and I stand infront of a six foot high wall, then moving backwards to lets' say 1 mile away.

Firstly, my height remains at six foot, the wall remains at six foot.

Why then does the wall appear to be a fraction of it's true size?

Why does it not remain as large as it previously appeared in my field of view?

This is not a question about the angles or otherwise of our visual capabilities as humans, this is a fundemental question about why objects seem smaller the further their distance?!

I am finding it hard to believe that no-one understands my question.

Strip away everything you have ever learned and then answer

Answer 1

This one is pretty easy.

Light enters your eye from a large area nearly 160deg horizontally and 130deg or so vertically. So lets draw a picture.

eyeball. . . . . . Field of view

. __. . . . .__---\. . .=
/. . . \_---. . . . . \. .=
\___/. ---__. . . ./. .=
. . . . . . . . . .---/. . =

If the object is near it takes up a large portion of your field of view. But if the object is far away

eyeball. . . . . . . . . . Field of view

. . . . . . . . . . . . . . . . . . . . . \
. . . . . . . . . . . . . . . . . . . . . .\
. __. . . . . . . . . . . ____-----\. . .=
/. . . .\____-------. . . . . . . . . \. . =
\___/. . . . .-------____. . . . . /. .=
. . . . . . . . . . . . . . . . . . .-----/. . .=
. . . . . . . . . . . . . . . . . . . . ./
. . . . . . . . . . . . . . . . . . . ./
It doesn't take up nearly as much of the field of view. Your brain, which has evolved to determine sizes and distances so we may hunt better, tells us the object is small. For those of us with two functioning eyes though, we are able to use desparity to determine an object's distance. Our brains then tell us the object isn't an inch tall and up close but rather 50ft away and 6 feet tall.

Answer 2

The screen in the retina of our eye is small compared with the size of objects.

All objects form an image in our eye.

The image size and objects size depends upon the distance between them.

Therefore, the geometry of distance and angle can alone explain the things.

Already there are answers to explain things with angles and distances.

Coming to your fourth question, you have stated that you are 6 ft tall and you are in front of the 6 ft wall. First think, how can you say, the wall is 6ft.

Your eye is at a height of approximately 6 ft from the ground. When your eye is very close to the wall, you can’t see the foot of the wall; you can see only a small portion of the wall; then how do you say that the wall is 6 ft.

You take a cardboard cylinder of 1 ft or 30 cm length and radius of 2 cm.

View the objects through the cylinder, first nearest objects and slowly view objects which are far away.

When we use this cylinder we must see only an area of pi x 2 x2 square cm area.

But using this cylinder, we can use it to see the moon, which has enormous area.

You do similar experiments and you will understand the answer your self.

Another important thing is a small image in the retina of our eye alone makes our brain visualize all objects as big and small.

With out angles and distances and simple geometry, it is difficult to answer your question.

Answer 3

You are right about things looking smaller at distance. Just look at the photos you have taken. Some of it IS an illusion though. Look at the full moon when it is straight over your head. Size it up by extending your arm and compare it to the size of you thumb nail. Later look at it when it first comes up or when it sets. The moon looks much bigger. Now, extend your arm and do the measurement again. It is still the same size. That is the illusion.

You have received answers saying it has to do with angles. You don't like them, but, unfortunately it is true. The back of the camera or your eye can only SEE what is in the field of view within certain angles. As you move away from objects more things come into the field of view and the only way to put all of the extra stuff into that field, without distortion, is to make them smaller.

We have zoom lenses on our cameras to help make stuff big again. Hubble Space Telescope is the best one I've seen. For us people though we have to use our brains to sort out much of this info. Check out this link to see if it can help. I hope it can help in your quest.

Answer 4

There are some good answers here!
Maybe your question is about size constancy ie, a football and a tennis ball can appear the same size if they are at different distances from your eyes, even though they are obviously known to be different sizes!
The answer is difficult, but basically it is a learnt phenomena of the visual system. For a true understanding you would need to read some Child Development Psychology books.
To illustrate my point, there is a documented case of a man who was born blind but had his sight restored (well, he never had it in the first place - so restored is not entirely correct) after an accident. He was unable to understand depth perspective or distance, and would often try to climb over balconies in blocks of flats or reach out for distant objects. After a couple of years he committed suicide through sheer frustration!
Maybe i haven't answered what you asked, but hopefully i have given you a useful perspective towards you answering your Question!

Answer 5

You can turn your question on it's head- if you move right next to a six foot high wall, you might only be able to see one brick of it, if your face is right next to the brick, you couldn't see much more. The wall remains six feet tall, you remain six feet tall, but your vision is blocked by a single brick. That's the view at six feet from the position you're in.

Let's say the wall is on a flat plain then, and you move, maybe 100 metres away from it... in the view from six feet up 100 metres from't wall, it's looking smaller, that's what you're on about. In a sense, I suppose you could say that your view is still blocked- blocked by clarity. You can see more of the plain, more of the sky, less of the wall- even though the wall is still blocking a little bit of your field of vision, the rest is blocked by other objects.

Hmmm... so, perhaps you are also questioning why something like the sun doesn't appear immense all the time- it's huge, right? But we can block it from our vision with a hand if we decide.

I recall a line from a Marillion song, I'm sure they nicked it from somewhere else- 'We don't see things as they are, we see them as we are'. Mind you, that's bringing subjectivity into it. That would be like- 'I think the wall is going to get smaller... and... it has!"



So, your vision is completely objective. The wall is six feet tall, you're six feet tall (you lucky person!), and you move away from it, and it seems to get smaller. But that's just the appearence. The wall remains six feet tall, you remain six feet tall, the ground is completely flat... you move along the plain until the wall is just a dot you can block out with your hand. But you are seeing the six foot wall, it remains that way... that's what it looks like from a distance. But why? Is all sight a blindfold? Are the senses ultimately defunct by their own limitations?

I'm going with the 'vision blocked by clarity thing' That which is six feet tall is so always, but the way it seems differs from observer to observer. If you are three feet tall regarding the six foot wall, it seems twice as big, though it is the same. Everyone has a point of reference, defined by themself, and as they move in time and space, it changes. That brings in the Marillion lyric a bit too... The wall hasn't changed, it's the person looking at the wall and s/his rotten clarity blockage.

I'm intrigued that you're trying so hard with this, so that's my stab at the problem. I failed to forget everything I ever learned. If I had the answer would have been something like- 'it's far away, that's why' Hope you reach enlightenment over it soon anyhow.

Answer 6

It is all to do with 'Peripheral Vision'

This is a fixed value and can be measured.

Stand close to the edge of a door and you will have difficulty in seeing top and bottom simultaneously.

Look towards the rear edge of a door, which is further away, and your 'fixed' peripheral vision allows you to see more and the brain interprets this as being smaller in comparison with the original view. The brain tries hard to interppret the signals it receives but can be fooled as with optical illusions.

The end result is that parallel lines appear to become closer, the further away they are.

This is a useful facility as perspective depends upon 'vanishing points'. Perspective allows us to visual objects in 3D.

This is a layman's description. If you wish to have a technical description then you will have to submit to a discourse on wide angle and telephoto lens, the structure of lens (remember the eye has a lens), convex and concave elements refraction and similar topics. The optics of a telescope and microscope should also help you.

Answer 7

OK, here's my attempt, but I don't think I'll strip away everything I've ever learned, if that's OK. I'm sure to need it at some point.

It's to do with your field of vision. Let's say that if you're looking straight ahead. Without moving your head you can see things straight in front of you (0 degrees), you can also see, say 45 degrees up, 45 degrees down, and 45 degrees to either side. These angles are probably wrong, but that's not important. Imagine your field of vision as a cone spreading outwards from your eyes. The angles of the cone are fixed.

If you press your face against a wall, it entirely fills your field of vision and appears huge. You can only see the wall, because it extends outside of the range of your field of vision in every direction.

But if you step backwards 10 metres away from the wall, the angles of your "field of vision cone" remain the same (of course), but now the wall looks smaller because it no longer fills your entire field of vision.

Now you've stepped back, there's room in your field of vision to incorporate the other objects around the wall as well. So the wall appears smaller as it now fits comfortably inside the angles of your "field of vision cone".

Answer 8

While I am far from qualified to answer this question, here is my thought.

NPR once had a report on a lady that was cross-eyed as a child and had several unsuccessful operations to fix it. Meanwhile, some other scientists did studies with baby cross-eyed lab animals and concluded that being cross-eyed at a young age ruined their brain's ability to see three dimensionally. How they knew this, I know not.

But this lady that was cross-eyed was asked a question by a scientist if she was missing out on what other normal-eyed people see and she answered no.

This lady somehow ended up at an unconventional doctor's/scientist's office that had her do some visual exercises to strengthen her brain's ability to see things like the rest of the world does. She followed her doctor's orders.

The exercises worked and the once cross-eyed lady was cured, proving that the lab animal-testing scientists were wrong.

She told a story of being in the snow and actually seeing in three dimensions. Before her exercises, she would see snow as though it were falling as a flat sheet in front of her face. After her exercises, she experienced being in the snow with it falling on and around her.

So to answer your question, maybe things farther away appear smaller because we see in thee dimensions, that is, we are able to see the distance between the six foot fence and yourself. Since there is a mile between you and the fence, it puts your height and the fence's height into perspective. If we weren't able to do so, everything would be seen as a single unit, like a two dimensional cartoon.

Good thought provoking question. Thanks for posing it.

Answer 9

The previous answers show a lot of intuitive understanding of the problem, but aren't giving you what you're looking for. Try this:

The sensation of 'size' is the actual size of something DIVIDED by its distance from you. This is mathematically identical to the angular field of vision occupied by the object, and proportional to the size of the image cast on your retina by the lens of your eye.

Since the distance is in the denominator, it's clear that twice as far away will appear half as large, etc

Answer 10

I understand your question.And it is difficult because we never ponder it.Lets start with this. Light reflects off objects and enters our eyeball. Something farther away is only reflecting a tiny portion of the total reflected light in your total field of view.In other words a little two inch in diameter mirror that is three miles away is undetectable.now when that same mirror reflects light all of a sudden you can see this effect makes it very detectable because of the light that it is reflecting.An object that is farther away reflects a lower intensity of light than an object that is closer. I also think that the depth perception is hinged on the fact that light reflecting off of objects farther away takes a fraction of a second longer to reach our eyes than objects that are up close.whew, my head hurts now.Hope that helped.