Re: Poll on *Really* Wide Angle Lenses


"David J. Littleboy" <davidjl@xxxxxxx> wrote in message
news:ddq0od$sms$1@xxxxxxxxxxxxxxx
>
> "Nostrobino" <not@xxxxxxxxxx> wrote in message
> news:9KmdnZUXXeJeGZ3eRVn-jA@xxxxxxxxxxxxxx
>>
>> "Chris Brown" <cpbrown@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>> news:5gk4t2-vn6.ln1@xxxxxxxxxxxxxxxxxxxxxxx
>>> In article <NfGdnc-R3sQlp2LfRVn-3w@xxxxxxxxxxx>,
>>> Nostrobino <not@xxxxxxxxxx> wrote:
>>>>
>>>>>>I don't
>>>>>>think "projection" is a useful paradigm for the mechanism of human
>>>>>>vision.
>>>>>
>>>>> Light is focused through a lens onto a surface to form an image - what
>>>>> else
>>>>> is that if it's not a projection?
>>>>
>>>>That *is* a projection.
>>>
>>> Do make your mind up.
>>>
>>>>It is *not* all there is to human vision. Again, you
>>>>are trying to write the brain out of the equation. What happens in the
>>>>eye
>>>>itself is only the beginning of the very complex process that is human
>>>>vision.
>>>
>>> This is an equivocation.
>>
>> No, it's the way things are.
>>
>> I realize that you would like to reduce human vision to some simple,
>> easy-to-understand proposition (and a two-dimensional one at that!) but
>> it can't be done. Human vision is an extremely complex thing. And it's
>> three-dimensional too, by the way. (Unless you're a cyclops.) Try to work
>> that out on your "2-dimensional spherical projection."
>
> This is amusing to watch from the sidelines, since you've both got valid
> points.
>
> Human vision, at the naive/intuitive/perceptual level, is a funny thing,
> since we construct what we think we're seeing from an arbitrary scan with
> the high res center based on hints from the low res peripheral vision.
> It's hard for photography to simulate that, since it's an active system.

I would say not only hard, but probably impossible.


>
> But at the imaging level, it's a projection onto a curved surface.

Yes. There has never been any question about that.


> And the information available to the processing system is what Chris says
> it is.

More or less. The lens of the eye has only a single (presumably aspherical)
element, and exactly what image it forms on the (imperfectly spherical)
retina frankly I have no idea, and I doubt very much that Chris does either.
He seems to believe that it follows the rules of spherical geometry, i.e.
that a straight line in front of the eye but off axis is reproduced as a
spherical-geometrically correct line on the curved surface of the retina,
and that this (since he has mentioned it about 17,294 times) is an important
fact. I have no idea whether the image is or isn't reproduced spherically
"correctly" on the retina, but regard that as unimportant anyway. The
important thing is not the exact form of the retinal image itself, but how
the brain translates it into the perception of (in this example) a straight
line.

To say or suggest that human vision is simply a matter of "light . . .
focused through a lens onto a surface to form an image," as Chris does
above, is analogous to saying that hearing (also a very complex process)
simply consists of sound waves striking a diaphragm.

Keep in mind also that this whole spherical-projection thing is a side issue
and a digression. The basic argument here is about the rules of perspective.
All a rectilinear lens can properly do is follow those rules accurately, and
within reasonable tolerances that's what rectilinear lenses do. Chris
*objects* to that, and has calls it a "bug." He insists that same-sized
objects farther away should look smaller, just as they do to the eye when
looked at directly, even when the lens axis is perpendicular to the plane
being focused on. Explaining to him that that's simply impossible in a
flat-field rectilinear lens and is not even desirable (since it would
grossly violate the rules of perspective) makes no impression on him. He
either a) has no grasp of the principles of perspective, b) doesn't care
about these principles, or c) is just offended by the whole idea of
perspective and wants it stopped. Or some combination of these.

N.


.

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