Seeing Beyond: How the Brain Creates 3D Image

[hjhgfj]

How the brain creates 3 dimensional image (what you see) from information that photons carry to your eyes? Photons travel with constant speed so your brain can't calculate how far object is from their velocities. I know stereoscopic vision helps to calculate distance from objects but even when you close 1 eye you can tell that some objects are farther and some are close. Shadows helps to create depth of field for your brain but I doubt It is the main factor.

 

[A.T.]

I know stereoscopic vision helps to calculate distance from objects but even when u close 1 eye you can tell that some objects are farther and some are close.

Because you have memory and know the environment. In a completely unfamiliar environment it would be very hard with one eye. You could potentially get some depth info from lens focus adjustments, needed to make objects sharp.

Shadows helps to create depth of field for your brain but I doubt It is the main factor.

The main factors are stereoscopic vision (close range), knowledge of object sizes (long range) and partial occlusion of distant objects by closer objects.

 

[hjhgfj]

Thanks for explanation but there are 3 things I still doesn't fully understand:

1.If you can tell object distance by sharpness (beams reflected from far objects are more parallel than beams reflected from close objects) how your brain can tell which beam is from which object (the beam from far object will get to your eye a bit later but I doubt a brain can spot that little time difference considering how fast light is).

2.if telling distance by sharpness is possible why there are these images where you can't tell if object is far or close - or is it because they are shown on a flat screen and you could tell a difference in real life?

3.Why stereoscopic vision works only for close distance (Is it because far objects beams are more parallel?) - I ve heard that they can tell how far away stars are by making pictures from 2 points of Earth's orbit - stars are rather far away so how does it work here

 

[A.T.]

1.If you can tell object distance by sharpness (beams reflected from far objects are more parallel than beams reflected from close objects) how your brain can tell which beam is from which object (the beam from far object will get to your eye a bit later but I doubt a brain can spot that little time difference considering how fast light is).

What does time have to do with focusing the light rays on the retina with the lens?

2.if telling distance by sharpness is possible why there are these images where you can't tell if object is far or close - or is it because they are shown on a flat screen and you could tell a difference in real life?

Yes, obviously it doesn't work with a flat screen.

3.Why stereoscopic vision works only for close distance (Is it because far objects beams are more parallel?)

The change in angle per change in distance is smaller

I ve heard that they can tell how far away stars are by making pictures from 2 points of Earth's orbit - stars are rather far away so how does it work here

Those 2 points of Earth's orbit are further apart than your eyes.

 

[hjhgfj]

What does time have to do with focusing the light rays on the retina with the lens?

I mean a light from distance object will get to you eye quicker so maybe in theory it could be used to calculate distance but I doubt it would be possible in pratice but my question here is:

If you can tell object distance by sharpness (beams reflected from far objects are more parallel than beams reflected from close objects) how your brain can tell which beam is from which object?

Yes, obviously it doesn't work with a flat screen.

So you would be able to tell difference from that specific perspective in real life (even using only 1 eye) ?

Those 2 points of Earth's orbit are further apart than your eyes.

But stars also are like zillions times farther away than objects you see everyday on earth

 

[A.T.]

how your brain can tell which beam is from which object?

Object recognition is a topic on itself, even though somewhat related to depth perception.

So you would be able to tell difference from that specific perspective in real life (even using only 1 eye) ?

Yes, see:
http://en.wikipedia.org/wiki/Depth_of_field

But stars also are like zillions times farther away than objects you see everyday on earth

That's why you cannot tell which star is closer by using your stereoscopic vision

 

[davenn]

.....Yes, see:
http://en.wikipedia.org/wiki/Depth_of_field

for a camera lens yes for the eyes NO and I have that from personal experience
I have a nasty double visioning problem at the moment that means I have to do a lot of things with one eye

focussing over a wide range of distance is not a problem, eyes do that well. My distance perception is completely shot to hell
anything from bring a wire, solder and soldering iron together at the same point to driving and not being able to tell distances
to other vehicles etc around you, is a total nightmare

Dave

 

[phinds]

I have a nasty double visioning problem at the moment ...

Is it Graves? I've been fighting that for 2+ years but sounds like mine isn't as bad as what you have. I DO experience some difficulty w/ depth perception and yeah, it can be scary when driving.

 

[davenn]

hi phinds

had to google Graves disease ... no not that altho prior to blood tests, that was the considered cause
the testes proved it to be Myasthenia Gravis, which is yet another type of auto-immune disease

I sympathise it really sux :( been a year for me and they ( after 2 different eye hospitals and several specialists )
still haven't sorted out what to do about it

I have almost given up driving at nite ... the wife will instead

cheers
Dave

 

[A.T.]

for a camera lens yes for the eyes NO

It depends. If a screen 50cm from your eyes shows a photo of very near and very distant objects, then you can definitely tell it from the actual real world, with just one eye. If a screen 10m away shows a picture of the night sky with distant stars, then it is difficult to tell the difference, even with two eyes.

 

[sophiecentaur]

An important idea is missing from this thread - in which the OP asks how the brain creates the image we are aware of; Psychology. The fact is that you do not actually need to 'see' a scene with your optical system, to appreciate the spatial relationship between objects in the world around you. You never (need to) look inside your mouth or at the back of your head but you still have a very good idea about the spatial layout. It's all too easy to get talking about binocular vision as being how we get depth information but there are millions of people with useful sight in only one eye*. *They can operate perfectly well in everyday life and may only find problems in a limited number of circumstances (3D Cinema being one - but that is totally artificial {stereoscopy}). Totally blind people have a surprisingly good idea of room layouts (much better than a sighted person could conceive of). What happens in our brains is much more complicated than what has been discussed so far. 'In there' somewhere, we assemble a three dimensional model of what's around us (using our memory) and we use whatever senses we have available to update it constantly with whatever information we can grab. We are really 'fooled' into experiencing 3D information by 2D images which use perspective and, particularly, 2D moving images in which the camera changes its viewpoint.

A brief search with terms such as 'machine vision' shows how much more there is to getting useful 3D information about a scene or object than in the Optics and Imaging involved.

** I would suggest that it is the survival value of the redundancy factor of having two eyes that is the most important factor. Binocuar vision is probably of secondary Darwinian importance. Grazing animals do not use their two eyes for binocular vision as much as for all-round vision.

 

[rcgldr]

Wiki articles:

http://en.wikipedia.org/wiki/Depth_perception

http://en.wikipedia.org/wiki/Stereopsis