Do lenses in our eyes and cameras distort reality?

[maclean]

Hello all,

Just wanting to vent out my thinking and see if there are some of you that have some wizdom on it...

I guess I've been wondering since taking some photos without a lens on my camera and noticing the blur that was recorded...

Now I'm led to belive that our eyes have a lens that projects light onto our sort of biological light sensor, but the thing that gets me confused is that a lens distorts (or should I say refracts) light doesn't it?

So why have we evolved so that in order to understand our surroundings, the light must be distorted first via a lens?

If our eyes did not have a lens, would we see something like a phtograph taken without a lens? And is this a more accurate representation of the photons that surround us than our own vision or am I way off the mark here?

The thing that gets me even more confused is that when looking at a photo taken without a lens, its then going through the lens on my eye isn't it lol.

[jimmyjamjoejoe]

Perception is a strange subject. Who's to say what's real and what isn't? What we see and experience is nothing more than a "filtered" universe. Even just using sight as an example, we only see a tiny portion of the electromagnetic spectrum as visible light. Who's to say our other senses aren't similarly retricted? We have a certain range of audible sounds...

To take things further, who's to say there isn't some sense that we just don't have, that's used to detect something that we currently don't even know exists? There could be a whole new type of energy/matter out there that we as a race just cannot detect or experience, but would that make it any less real?

[RogerTheDodger]

It's the other way round, we have learned to interpret what we see. The was a great experiment that had people wear a device that inverted their vision so everything was upside down, the brain accommodated it after a time.

[sologuitarist61]

I always thought that the eyes lens served the same purposes as that on a camera, without the lens you just get light and not a representation of what you are actually looking at. In other words, without the lens nothing is in focus and we would have no idea as to what was actually there.

[Cath]

To confuse the matter even further ..

We can't actually see anything we are looking at, we are just seeing reflected light, not the object itself

[Alastair Rae]

An old question: http://en.wikipedia.org/wiki/Allegory_of_the_Cave

[JamesF]

So why have we evolved so that in order to understand our surroundings, the light must be distorted first via a lens?

If our eyes did not have a lens, would we see something like a phtograph taken without a lens? And is this a more accurate representation of the photons that surround us than our own vision or am I way off the mark here?

A lens isn't a necessary part of the system. A pinhole camera, for example, doesn't have one. However having a visual system that can adapt to varying light levels clearly has to be an evolutionary advantage over not doing so for us. If you achieve that by having an entrance to the visual system that is capable of dilating then you immediately run into trouble because the light coming from a single point in the environment can spread over an area of the "sensor" and the light from different points in the environment may overlap. There may be ways to unpick that mess without using a lens to focus all the light from a single point back onto a single point on the back of the eyeball, but nature presumably didn't find one during our evolution, or a lens worked better and evolution took its course.

There are other types of eye however -- the compound eyes of some insects, for example. Perhaps if we had compound eyes the physics of our vision would be completely different. Whether insects see a more "accurate" representation of reality I have no idea. Depends what you mean by "accurate" You might look at what a lens does as creating a situation where reality is more comprehensible. If you view that as "less accurate" then perhaps that is actually an advantage. For example, you are unaware that your eyes are almost constantly moving, because your brain "turns off the signal" when they're in motion. In one sense that makes them "less accurate" in that you're not perceiving what's really going on. On the other hand, if you were able to do so you might well have trouble keeping your lunch down.

James

[acey]

The lens of the eye focuses light on the retina, which sends signals to the brain, which gives us the perception of sight. As an optical system, the eye is prone to all the usual sort of aberrations (I wear glasses to correct astigmatism). The effect of chromatic aberration is minimised by having the colour-sensitive cells (cones) concentrated on a small area (the fovea) - if they were spread evenly across the retina then we would probably see false colour fringing.

Having the pupil too large would also increase aberration because of the very short focal ratio that would result. The eye compensates by having reduced sensitivity at the periphery of the retina (the Stiles-Crawford effect). When the pupil is very small diffraction dominates: this places a limit on how high a magnification you can use on a telescope. Diffraction becomes severe for pupil size less than about half a millimetre or a fiftieth of an inch, hence the advice to limit magnification to 50 times aperture in inches (i.e. an exit pupil of a fiftieth of an inch).

Optically, the eye performs best when the pupil size is around 2-3mm. Evolution has arranged it so that our pupils tend to dilate to around this size in sunlight conditions, when we should be out hunting mammoths. This is also the sort of exit pupil size that many observers reckon gives the most enjoyable views.

[ollypenrice]

In some cases reality distorts reality. My house is always the same size but sometimes it looks smaller. This is when I'm further away. It doesn't change size, but it really is further away and my eyes are telling me this, so which reality do you prefer? The one with the distance factored in or the one without?

If we look at a long straight wall blocking our paths some distance away this wall (which is of a constant height) will appear to get less tall at either side than it does directly in front of us. Its top and bottom edges will appear curved. This is true of the 'reality' of the effects of perspecive due to distance but not true of the 'reality' of the wall. So I suspect that it might be better to say that our eyes are good at showing us our relationship with things but not so good at showing us the things themselves.

Ancient Greek architecture looks supernaturally rectilinear and symmetrical because it is in fact full of curves and assymetries designed to compensate for the effects of distance and light or shadow.

Pity my father is no longer with us. He was an academic in this intriguing field and would have greatly enjoyed the conversation.

Olly

[Qualia]

If our eyes did not have a lens, would we see something like a phtograph taken without a lens? And is this a more accurate representation of the photons that surround us than our own vision..?

An important ingredient to that representation is the mind, for what is the given perception independent of a mind? And I think this is a meaningless question, for the very question of what something is as representation already presupposes a mind to measure and cognize it. In another universe, if the physiology of our eyes turned out to not have a lens, but let's say all camaras did, would it make any more sense to ask, if our eyes had lens would we see something like a photo and would this be a more accurate representation of 'reality'?

Evidently, perhaps, 'roses' can exist without us but exist as what, however?

Every property perceived or represented of a rose, lens or no lens, is a mental event. If you take away all minds, what is left of the rose? As soon as you try to describe what is left of it, you are already importing a mind into the discussion, but, for the sake of argument, by trying to just focus on the lens, we have eliminated all minds. There is a conumdrum and one that I think is impossible to give an answer to.

[ollypenrice]

^^ WOT, a philosopher stuck for words???

This cannot be! (Don't listen to me, though. When I received my finals results and a letter from my Prof he was happy enough with my main subject but concluded darkly, 'Your Philosophy, however, was less successful...'

Olly

[foundaplanet]

).

[maclean]

Thanks for all the input guys, looking at my question now and reading some of your responses, I realise that my questions are not straight forward and slightly invalid in some ways.

My head is absolutly buzzing! I guess the problem lies in the fact that our perception of reality is simply a translation from our sensors such as our eyes sending electrical singals to our brain to be 'seen' in the mind.

So as I look at this computer screen now, it makes total sense in my head, but the image im seeing is just an electrical signal interprited in my brain! I guess the problem is that reality can be interprited in many ways and who or what is to say one way is more accurate than the other.

I love this stuff so if anyone has anything else to say or any more links to post realated to it please do!!

Thanks all!