Would we be able to see further if we had bigger eye-balls?

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Offline Chemistry4me

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Would we be able to see further if we had bigger eye-balls?  [:o]

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Offline lightarrow

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Would we be able to see further if we had bigger eye-balls?
« Reply #1 on: 12/04/2009 11:19:41 »
Would we be able to see further if we had bigger eye-balls?  [:o]
Do you want to replace your eye-balls with watermelons?  [;D]

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Offline Chemistry4me

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Would we be able to see further if we had bigger eye-balls?
« Reply #2 on: 12/04/2009 11:49:15 »
Well, if it'll help me see better then YES!

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Offline Chemistry4me

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« Reply #3 on: 12/04/2009 12:09:23 »
Perhaps I have not explained myself properly? I was thinking if we had a bigger lens would we be able to see further (i.e, have higher visual acuity)?

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Variola

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« Reply #4 on: 12/04/2009 13:09:33 »
Perhaps I have not explained myself properly? I was thinking if we had a bigger lens would we be able to see further (i.e, have higher visual acuity)?

I think its more to do with the structure than the actual size, falcons and other birds of prey can spot small rodents hidden in the grass from way up high, yet their eyes are quite small.

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Offline Chemistry4me

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« Reply #5 on: 12/04/2009 13:11:24 »
Thank you for your comment. [:)]
At least we're getting somewhere. [::)]

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Offline Yomi

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« Reply #6 on: 12/04/2009 13:17:28 »
We can say that size doesent really matter in sense organs I think Hawk or an Eagle can point out their prey from high distance wven the diametre of eyeballs is just about 1-2 cms!!!!! Quiet amazing creatures....... [::)] [::)] [::)] [::)] [::)]
MAHESH

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Offline Chemistry4me

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« Reply #7 on: 12/04/2009 13:18:29 »
So what are they doing different to us that makes them see better?

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Variola

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« Reply #8 on: 12/04/2009 13:18:46 »
We can say that size doesent really matter in sense organs I think Hawk or an Eagle can point out their prey from high distance wven the diametre of eyeballs is just about 1-2 cms!!!!! Quiet amazing creatures....... [::)] [::)] [::)] [::)] [::)]




There is an echo in here... lol

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Offline Chemistry4me

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« Reply #9 on: 12/04/2009 13:19:45 »
And I said we were getting somewhere? No? [:D]

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Variola

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« Reply #10 on: 12/04/2009 13:28:55 »
http://videos.howstuffworks.com/hsw/21716-birds-of-prey-the-eagles-eye-test-video.htm

Run it along towards the end of the video,till about 3.30, more of an explanation on how the eagle's eye works.

Apparently their eyes are big for their body ratio, if ours were the same size they would be as big as oranges. They also have a large iris,which allows a bigger picture to be projected onto the retina.On the retina there are light sensitive receptors called cones, which code for colour and detail. Eagles have 600,00 cones per sq mm, 4 times as many as humans.

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Offline Chemistry4me

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« Reply #11 on: 12/04/2009 13:30:35 »
Okay, forgetting about the cones for a second. If we had eyes the size of oranges our vision would be improved right? [:)]

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Offline graham.d

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« Reply #12 on: 12/04/2009 13:54:14 »
Well the size of the aperture would enable better seeing in low light levels, though the lens has to be more complex to prevent aberrations and worse acuity. But generally, if the eyes were bigger it would enable a greater density of receptors and greater light gathering capability. I guess we have evolved eyes that are adequate for our use. It would be hard to see how a complex lens could have "evolved".

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Offline lightarrow

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« Reply #13 on: 12/04/2009 17:32:56 »
Okay, forgetting about the cones for a second. If we had eyes the size of oranges our vision would be improved right? [:)]
At least this is what astronomers must have thought, otherwise we can't explain why they have constructed even greater telescopes... [8D]

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Offline graham.d

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« Reply #14 on: 12/04/2009 18:46:18 »
In astronomy it is important to have a very large aperture because the light levels are extremely low. You can also avoid aberrations by using a parabolic reflector. This concept has never evolved naturally - I blame biologists :-)

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Offline LeeE

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« Reply #15 on: 12/04/2009 19:39:21 »
Basically, what graham.d has said.

The question is actually rather mis-phrased.  What I think it should have said is "would bigger eyeballs increase the resolution of our eyes?  After all, we can all see the same 'distance'.

There are two factors at play here; the lens and the image-detector.

Assuming the same field of view, if the larger eyeball has a larger image area but the same density of photo-receptors as a normal eyeball then there will be more total receptors across the image area in the larger eyeball, increasing its resolution.

However, a larger lens just allows more light through, making the image brighter.  Even with our normal eyeballs though, unless it's pretty dark, the iris is normally contracted to reduce the amount of light entering the eye because it would otherwise be too bright.  With the same photo-receptors in a larger eye then, the iris would still have to contract to the point where the light levels reaching the receptors is the same as for a normal eye, so in bright light the size of the larger lens in the bigger eyeball has to be reduced anyway.

Another relevant factor are the imperfections in the lens.  If the number of imperfections in the lens is the same per unit area then the larger lens will have more imperfections in it, which will reduce it's resolution compared with a smaller lens.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline lightarrow

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« Reply #16 on: 12/04/2009 21:27:12 »
In astronomy it is important to have a very large aperture because the light levels are extremely low. You can also avoid aberrations by using a parabolic reflector. This concept has never evolved naturally - I blame biologists :-)
Ok, let's say you want to make observations in a clear, bright day. Assuming the same kinds of lens qualities, would you choose a little or a bigger telescope/binocular for a greater resolution?

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Offline graham.d

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« Reply #17 on: 12/04/2009 21:51:51 »
If you are talking about a simple, single lens, then it would be fairly small. Not so small as to get distortions because of diffraction, but big enough to capture an appropriate amount of light for the sensitivity of the sensors. 35mm camera design over the years is a good example. A simple single lens of focal length of (say) 50mm gives just about acceptable performance with an aperture of f4.5. Better lenses developed in the early 20th century (like the Tessar lens) comprised 4 elements and worked well at f2.8. Modern many element lenses are good at f1.4 or wider. All these lenses are optimum for resolution at a stop or two smaller aperture and all the lenses will start to have diffraction problems at f22 of smaller. 

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Offline Chemistry4me

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« Reply #18 on: 13/04/2009 03:59:44 »
That's fascinating stuff. [:)]
You want me to change the title of the thread LeeE (even though I know you have a thing against it)?

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Offline stereologist

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« Reply #19 on: 13/04/2009 04:31:57 »
Take a look at the eye of the horseshoe crab. This creature has mastered 3 methods that allow the eye to perceive images over an amazingly wide range of light intensities.

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Offline Chemistry4me

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« Reply #20 on: 13/04/2009 12:41:04 »
Okay, so if you were to sum up the answer to the question in three sentences, what will it be?

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Offline graham.d

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« Reply #21 on: 13/04/2009 13:35:58 »
Can I write very long sentences? :-)

It is really hard to do this because your question needs many caveats to answer it properly.

1. Simply making the eye bigger does not help because it needs more doing to it, such as adding more receptors and/or a more complex lens.

2. If we assume that the size of an individual receptor (like a pixel) is fixed and that the basic eye design should not change, then making the eye bigger will create a larger area of receptors for the same field of view and, providing the brain is changed to cope with the information, will give a higher resolution, thus enabling a proportionate improvement in the distance vision with the same light levels.

3. The same effect could be achieved by keeping the eye the same size and design but having more, and smaller, receptors; this is why a 20 Mega-pixel camera has better resolution than a 4 Mega-pixel camera.


The eye and brain are very complex in how they work together. An eagle, for example, has much better resolution than a human eye, not because of the size of the eye compared to a human eye, but because of the size, structure and speciality of the receptors (about 5x the density of the human eye). They have quite poor night vision though. Owls, in contrast, have very good night vision and have very large eyes compared to their head size. The eyes are fixed in their heads hence the remarkable, but necessary, head movements owls can achieve. Their brain sorts out the parallax problems that arise. All designs, whether created by humans or formed by evolution, are compromises that achieve what they need to for optimum use. Simply changing one of many features will alter the performance in one area at the expense of another.


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Offline Chemistry4me

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« Reply #22 on: 13/04/2009 13:42:29 »
Wow, thank you kind Sir. [:)]
You've made it fairly clear for me to see. [;D]
I don't think anyone can beat that.


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Offline Don_1

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« Reply #23 on: 13/04/2009 14:04:06 »
I guess we have evolved eyes that are adequate for our use.

I think this is the best answer to the question 'Why aren't our eyes as good as an Eagle's?' A bird of prey needs to fly high to enable it to see a very wide field, but it's eye must be capable of spotting prey from such a distance. Being able to see so well at great distances would be of no benefit if you could not then launch an attack at high speed. Since birds of prey do have the ability for high speed attack, the high resolution vision is supported. The two capabilities are necessary to be of use to each other. One without the other would be pointless.

Since humans have never had the capability of high speed attack on our prey, or the necessity, such high resolution vision would be pointless and could infact be counterproductive. Too much detail could lead to confusion.

As to this thread's question, I should think a larger eye would not be necessary for improved long distance vision. Perhaps an improved lens and retina might be all that would be required, along with an improved 'processor'.
If brains were made of dynamite, I wouldn't have enough to blow my nose.

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Offline lightarrow

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« Reply #24 on: 13/04/2009 14:59:35 »
As to this thread's question, I should think a larger eye would not be necessary for improved long distance vision.
Certainly, I agree with it. But it depends on how much "long distance". If you want to increase that distance a lot, before or less you'll have to increas the eye's dimensions.

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Offline LeeE

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« Reply #25 on: 15/04/2009 00:31:53 »
That's fascinating stuff. [:)]
You want me to change the title of the thread LeeE (even though I know you have a thing against it)?

Nope.  Many people would phrase the question that way and by reading the subsequent posts they might learn something about the question as well as the answer.

Plus, of course, subsequent posts referring to a mis-phrased question would then seem nonsensical.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline Don_1

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« Reply #26 on: 15/04/2009 12:19:17 »
As to this thread's question, I should think a larger eye would not be necessary for improved long distance vision.
Certainly, I agree with it. But it depends on how much "long distance". If you want to increase that distance a lot, before or less you'll have to increas the eye's dimensions.

I'm not so sure that this would be the case. I can look at the Moon, without the need for a telescope, and quite clearly make out the surface detail (to an extent). I think if I wanted to be able to make out more detail of a far distant object, it is more the sensor (retina) which requires extra capability than the receiver.

Let me explain my reasoning here.

Take a Nikon D40 - 6 megapixel DSLR body and fit a Nikon 85mm f2.8 lens. With the lens set to infinity, take a shot of an object on the horizon. Now, using your computer as the processor, enlarge that object to the maximum at which it remains discernable.

Now compare that with the identical shot, taken under identical conditions with the same Nikon 85 mm f2.8 lens, but using a Nikon D3x 24.5 megapixel DSLR body.

The extent to which this shot can be enlarged with the object remaining discernable will be much greater (approx. 4 X greater), yet it is the result from the very same lens and the same processor, only the sensor has been improved.

Our eye works in much the same way as this camera with a fixed focal length lens. We make sense of a particular object within our field of vision by focusing the lens on that object and then getting the brain to concentrate on it. With an improved sensor, we would be able to distinguish more detail of that object.

The eagle has an eyeball roughly the same size as a human, yet it can see far better than a human. The reason for this is that the human retina has 6.4m cones, 200k of which are in the fovea, the eagle has approximately 32m cones, 5 times that of a human. The back of the eagle’s eyeball is flatter and the retina bigger, but the lens is not much different. The brain works in a similar way to a digital zoom on a camera. It concentrates on one area of the whole picture. If that picture has a higher resolution, it can make more sense of the detail. In effect, we ‘digitally’ zoom in on an object.

If we (and eagles) were to be able to zoom in on an object optically, in the same way as a camera zoom lens, our eye would need to be restructured since eyes have a single element lens. To enable optical zooming, like a camera lens, eyes would need a multiple moving element lenses. This would create a problem, however, in that there would be a considerable loss of field of vision.

In conclusion, our eyeball does not need to be bigger in order to see further. We can see just as far as an eagle. What it needs is an improved retina in order to be able to discern more from a small area of that sensor.
If brains were made of dynamite, I wouldn't have enough to blow my nose.

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Offline Chemistry4me

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« Reply #27 on: 15/04/2009 13:21:08 »
So the Hubble telescope is just an eye with trillions and trillions of cones. Is that what you're saying?

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Offline graham.d

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« Reply #28 on: 15/04/2009 13:59:31 »
There are two factors (at least in the main, for this discussion) - resolution and sensitivity. To get more resolution you need more sensors looking at a particular field of view. There is a limit to how sensitive a receptor or photosensor can get. To get more sensitivity you need to increase the total light gathered by having as wide an aperture as possible. Astronomical telescope design has always been about trying to achieve this whilst keeping aberrations to a minimum because the amount of light arriving from distant stars is very, very small indeed. The other way to improve the light gathered is to stay "on-target" for a long time to integrate the total light gathered - a long exposure. Hubble does both of these things by having a large parabolic (at least it was supposed to be) reflector and very steady positioning with no nasty effects from the light passing through the atmosphere. 

In fact I just looked up Hubble and its CCD array (image sensor) is actually only 2.5 Mpixel, which is very poor by today's standards.
« Last Edit: 15/04/2009 14:06:28 by graham.d »

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Offline Chemistry4me

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« Reply #29 on: 15/04/2009 14:03:53 »
So larger eye-balls = more sensitivity? Assuming that everything else remains the same.

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Offline graham.d

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« Reply #30 on: 15/04/2009 14:08:18 »
Yes. The eagle, as I said (and also Don) gets more resolution because it packs more pixels into the same area.

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lyner

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« Reply #31 on: 15/04/2009 14:50:25 »
There are two factors (at least in the main, for this discussion) - resolution and sensitivity. To get more resolution you need more sensors looking at a particular field of view. There is a limit to how sensitive a receptor or photosensor can get. To get more sensitivity you need to increase the total light gathered by having as wide an aperture as possible. Astronomical telescope design has always been about trying to achieve this whilst keeping aberrations to a minimum because the amount of light arriving from distant stars is very, very small indeed. The other way to improve the light gathered is to stay "on-target" for a long time to integrate the total light gathered - a long exposure. Hubble does both of these things by having a large parabolic (at least it was supposed to be) reflector and very steady positioning with no nasty effects from the light passing through the atmosphere. 

In fact I just looked up Hubble and its CCD array (image sensor) is actually only 2.5 Mpixel, which is very poor by today's standards.
The field of view is also relevant.
The 2.5Mpx is enough for the field of view which is required and it probably reflects the fact that the resolution is largely diffraction limited in any case; more pixels would just produce the same amount of 'blurriness' in the final picture.
Getting a meaningful discussion about this sort of topic requires a totally holistic view - particularly where the Intelligent Designer is concerned. (Sorry- just kidding.)
« Last Edit: 15/04/2009 14:52:04 by sophiecentaur »

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Offline Don_1

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« Reply #32 on: 15/04/2009 15:30:13 »
You had me worried there sophiecentaur.

Look at this picture

[attachment=8022]

This was taken on my Nikon D300 12.3 mp and printed (slightly cropped)to 36" x 22"

If this had been taken on a 6mp camera, it would not be possible to print to this size without the diagonal lines being out of kilter. To get a print any bigger than this, I would need a camera with more pixels to its sensor.
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Offline lightarrow

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« Reply #33 on: 15/04/2009 15:44:14 »
As to this thread's question, I should think a larger eye would not be necessary for improved long distance vision.
Certainly, I agree with it. But it depends on how much "long distance". If you want to increase that distance a lot, before or less you'll have to increas the eye's dimensions.

I'm not so sure that this would be the case. I can look at the Moon, without the need for a telescope, and quite clearly make out the surface detail (to an extent). I think if I wanted to be able to make out more detail of a far distant object, it is more the sensor (retina) which requires extra capability than the receiver.

Let me explain my reasoning here.

Take a Nikon D40 - 6 megapixel DSLR body and fit a Nikon 85mm f2.8 lens. With the lens set to infinity, take a shot of an object on the horizon. Now, using your computer as the processor, enlarge that object to the maximum at which it remains discernable.

Now compare that with the identical shot, taken under identical conditions with the same Nikon 85 mm f2.8 lens, but using a Nikon D3x 24.5 megapixel DSLR body.

The extent to which this shot can be enlarged with the object remaining discernable will be much greater (approx. 4 X greater), yet it is the result from the very same lens and the same processor, only the sensor has been improved.

Our eye works in much the same way as this camera with a fixed focal length lens. We make sense of a particular object within our field of vision by focusing the lens on that object and then getting the brain to concentrate on it. With an improved sensor, we would be able to distinguish more detail of that object.

The eagle has an eyeball roughly the same size as a human, yet it can see far better than a human. The reason for this is that the human retina has 6.4m cones, 200k of which are in the fovea, the eagle has approximately 32m cones, 5 times that of a human. The back of the eagle’s eyeball is flatter and the retina bigger, but the lens is not much different. The brain works in a similar way to a digital zoom on a camera. It concentrates on one area of the whole picture. If that picture has a higher resolution, it can make more sense of the detail. In effect, we ‘digitally’ zoom in on an object.

If we (and eagles) were to be able to zoom in on an object optically, in the same way as a camera zoom lens, our eye would need to be restructured since eyes have a single element lens. To enable optical zooming, like a camera lens, eyes would need a multiple moving element lenses. This would create a problem, however, in that there would be a considerable loss of field of vision.

In conclusion, our eyeball does not need to be bigger in order to see further. We can see just as far as an eagle. What it needs is an improved retina in order to be able to discern more from a small area of that sensor.

Ok, can you show me in which way exactly you can device a camera 85 mm to discern two 1mm spots which are 1 mm far each other, on the Moon's surface?

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Offline dentstudent

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« Reply #34 on: 15/04/2009 15:55:55 »
Not sure that this has already been mentioned, but what about exposure? Isn't this a fundamental difference between a camera/telescope and an eye, which makes comparisons rather difficult? A telescope with a camera effectively catch photons over a pre-determined time period. This is how the Hubble is able to take such breath-taking shots of space, since it can sit and "look" at the same point in space and collect the infrequent photons that arrive. The eye can't do this.

In answer to Lightarrow's question, wouldn't it be possible to discern these two 1mm spots with a camera if you could get enough magnification, if you could keep the camera and lenses still enough, and if you could have an appropriate exposure time?

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Offline Don_1

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« Reply #35 on: 15/04/2009 16:45:44 »
lightarrow To discern 2 x 1mm points 1mm apart on the Moon's surface is rather going to the extreme. The sensor required for this, I think, would need 386,242.5 megapixels. This would mean fitting more than 10k times more cones on an eagle's retina, or 50k more times for a human. This would hardly be termed as 'being able to see a long way', this is rather into the realms of Superman! But I concede, that for such incredible vision, the eye would need to be very much bigger.

Can you make do with a telescope?

dentstudent The amount of light entering the eye (or camera) is a factor in what we can see. As you say, Hubble can keep still and gather a huge amount of light over a period of time, which we cannot. Some large format cameras of 100+ mp do require exposure times running into minutes.
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Offline lightarrow

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« Reply #36 on: 15/04/2009 18:38:19 »
lightarrow To discern 2 x 1mm points 1mm apart on the Moon's surface is rather going to the extreme. The sensor required for this, I think, would need 386,242.5 megapixels. This would mean fitting more than 10k times more cones on an eagle's retina, or 50k more times for a human. This would hardly be termed as 'being able to see a long way', this is rather into the realms of Superman!
No.
Not even Superman could do it, not even a sensor with infinite pixels/cm2, because of diffraction: the resolving power d of an optical system is d = λ/2NA where NA = numerical aperture and λ = wavelength; or you can consider the angular resolution: sinθ = 1.22λ/D where D = diametre of lens' aperture. Make the computations and you'll find that you can NEVER resolve those two points in the visible range with an 85 mm lens.

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Offline lightarrow

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« Reply #37 on: 15/04/2009 18:41:32 »
In answer to Lightarrow's question, wouldn't it be possible to discern these two 1mm spots with a camera if you could get enough magnification, if you could keep the camera and lenses still enough, and if you could have an appropriate exposure time?
See my answer to Don_1.

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Offline Bored chemist

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« Reply #38 on: 15/04/2009 19:29:18 »
According to this
http://www.bostonherald.com/news/international/general/view.bg?articleid=1081922
 you can see billions of miles already. Given the age of the universe, there isn't that much further to see.
A bigger eye would give, in principle, better optical resolution (ie the abillity to see two things close together as separate rather than as one blur) and also, for a giver size of retinal cell detecting the light it would alow a larger number of effective "pixels". Perhaps more usefull would be the ability to see better in low light conditions.
On the other hand, as has already been pointed out, eagles see better than us, and they have smaller eyes so we could improve things without making our eyes bigger.

Does anyone know what the typical angular resolution of the eye is and how it compares to the diffraction limit?
« Last Edit: 15/04/2009 19:31:18 by Bored chemist »
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lyner

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Would we be able to see further if we had bigger eye-balls?
« Reply #39 on: 15/04/2009 22:51:16 »
You had me worried there sophiecentaur.

Look at this picture



This was taken on my Nikon D300 12.3 mp and printed (slightly cropped)to 36" x 22"

If this had been taken on a 6mp camera, it would not be possible to print to this size without the diagonal lines being out of kilter. To get a print any bigger than this, I would need a camera with more pixels to its sensor.

I don't think your camera is diffraction limited. Did you use f100 as an aperture and a field of less than one degree?
Like I said, there's more to it than one simple statistic!
PS Have you got some dirt on your sensor? (Top left)
« Last Edit: 15/04/2009 23:38:49 by sophiecentaur »

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Offline lightarrow

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« Reply #40 on: 16/04/2009 01:35:22 »
Does anyone know what the typical angular resolution of the eye is and how it compares to the diffraction limit?
Very good question. It seems it's generally accepted as 1' (= 1/60 °) the angular resolving power of the human eye. With a pupil open of 4 mm the diffraction limit is just half of that value.

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Offline Don_1

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Would we be able to see further if we had bigger eye-balls?
« Reply #41 on: 16/04/2009 08:16:33 »
PS Have you got some dirt on your sensor? (Top left)

Yes, there was a speck of dust which I hadn't noticed until the print was done!

Details of shot:
Lens focal length 80mm ; f18 @ 1/1250sec ; ISO 200 ; re-colouring with Nikon Capture NX.
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Offline Don_1

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« Reply #42 on: 16/04/2009 09:06:22 »

Not even Superman could do it,

I think you will find all of that a mere trifle to Superman; he can do anything!

As BC has cottoned on, I am really being hypothetical and not taking distortion into account. In practice, even over a relatively short distance atmospheric distortion would render ultra long vision pretty worthless. But, by the same token, our brain does account for and correct distortion caused by our fixed focus lens. For starters, the image projected onto the retina is upside down. Looking at an object a few cms away causes this effect:

But our brain compensates for this and we see the object in a more natural way. Our brain also merges two different views to give us 3d vision.

The point I am making is that we do not need a bigger eyeball to see further. Again as BC pointed out, and as I said in a previous post, our eye can already see far distant objects. I cannot be sure of this, but I think V762 Cas (in Cassiopeia) is the furthest star from Earth visible to the naked eye. 15000 light years, I think is plenty far enough. Our eye's resolution, however, could be much improved with a sensor (retina) matching the quality of that of an eagle. Since the eagle's eyeball is the same size as a human eyeball, I see no need for a larger eyeball to improve our resolution.
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Offline Chemistry4me

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« Reply #43 on: 16/04/2009 09:08:47 »

The point I am making is that we do not need a bigger eyeball to see further....

Is that your final answer? [:)]

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« Reply #44 on: 16/04/2009 09:12:01 »

The point I am making is that we do not need a bigger eyeball to see further....

Is that your final answer? [:)]

Yes.
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Offline Chemistry4me

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« Reply #45 on: 16/04/2009 09:13:55 »
And is that the final answer that'll put me out of my misery?
How about a show of hands, you may vote for or against Mr. Don_1.

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lyner

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Would we be able to see further if we had bigger eye-balls?
« Reply #46 on: 16/04/2009 10:54:53 »
PS Have you got some dirt on your sensor? (Top left)

Yes, there was a speck of dust which I hadn't noticed until the print was done!

Details of shot:
Lens focal length 80mm ; f18 @ 1/1250sec ; ISO 200 ; re-colouring with Nikon Capture NX.
It was a 'normal' photograph, as I suspected.
Hubble doesn't take 'normal' photos. It looks at a very small area in the centre of the 'normal' field and those 'few' Mpixcels are placed where they are wanted. An enlargement of a Hubble picture would appear glubby because of the optics. If you magnify any telescope image beyond a limit, you always get the imperfections of the optics grinning through. More sensors in the array would achieve nothing which the normal filtering of the image would achieve.
As for the original question, the ultimate limitation of 'seeing' something at a distance, boils down to Signal to Noise ratio. A large diameter is necessary and that implies a long focal length. There isn't a simple answer to this, at all.

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Offline Chemistry4me

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« Reply #47 on: 16/04/2009 12:46:46 »
So altogether, what do we need to take into consideration here?

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Offline lightarrow

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« Reply #48 on: 16/04/2009 15:23:15 »

Not even Superman could do it,

I think you will find all of that a mere trifle to Superman; he can do anything!

As BC has cottoned on, I am really being hypothetical and not taking distortion into account. In practice, even over a relatively short distance atmospheric distortion would render ultra long vision pretty worthless. But, by the same token, our brain does account for and correct distortion caused by our fixed focus lens. For starters, the image projected onto the retina is upside down. Looking at an object a few cms away causes this effect:

But our brain compensates for this and we see the object in a more natural way. Our brain also merges two different views to give us 3d vision.

The point I am making is that we do not need a bigger eyeball to see further. Again as BC pointed out, and as I said in a previous post, our eye can already see far distant objects. I cannot be sure of this, but I think V762 Cas (in Cassiopeia) is the furthest star from Earth visible to the naked eye. 15000 light years, I think is plenty far enough. Our eye's resolution, however, could be much improved with a sensor (retina) matching the quality of that of an eagle. Since the eagle's eyeball is the same size as a human eyeball, I see no need for a larger eyeball to improve our resolution.
It's not about "distorsion", but about "diffraction limit", which cannot be overcome by *any* optical instrument, however perfect it could be. It's an impossibility of the *waves* of light, not a technical imperfection of the instruments.
« Last Edit: 16/04/2009 15:26:17 by lightarrow »

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Offline lightarrow

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« Reply #49 on: 16/04/2009 15:28:44 »
So altogether, what do we need to take into consideration here?
Ask astronomers why they don't have reproduced the optical capabilities of an eagle's eye (or more) in a telescope with the same dimensions. It's not mostly about technological limitations, but mostly because of the diffraction limit.
« Last Edit: 16/04/2009 15:30:48 by lightarrow »