On Mon, 14 Sep 1998 01:00:50 +0200, Helmut Dersch
>Neuman-Ruether wrote:
>> Hmmm, actually our eyes do receive the image inverted
>> and with straight lines off center curved. Our brains do
>> invert that image, but, oddly enough, do not straighten the
>> lines...;-) The softness of our off-axis sight, our tendency
>> to concentrate only on the extreme center of our vision,
>> the "cropping" provided by our facial features, and the
>> strong "learning" experience we have all been put through
>> (photographs, TV, movies, paintings, drawings, etc.) lead
>> us to believe what is not true - that straight lines viewed
>> off center of our vision are seen as straight... For more
>> on this, you may find my article "On Seeing and Perspective"
>> on my web page, under "I babble", interesting...;-)
>Sorry to jump in on this, but I just have to correct this
>often heard error about fisheye lenses being more natural.
Hmmm, seems to me the overwhelming preponderance of opinion
expressed is on the other side - I have been the lone voice of
reason and truth on this in a world darkened by the universal
(untrue) view of the rightness of rectangularity...;-), ;-), ;-)
>Of course, the rectilinear perspective is the correct one, and the fisheye
>image is distorted. This has absolutely nothing to do with human vision,
>learning or education: any animal or even any alien would come to the same
>conclusion. The (perfect) rectilinear lens creates a flat image which
>(if viewed from the right distance) is indistinguishable from the "real"
>3D-view (stereoscopic and out-of-focus effects aside).
Methinks you are proving what I said about "learned" views...;-)
>A fisheye image does not create
>this effect as long as it is flat (and normal prints as well as slide
>projection screens are flat). This is the distortion, which is completely
>independent of the viewer's eyes.
I think you are saying that the rectangular view is right because
rectangularity follows the rules of rectangular perspective - a bit of
a circular argument, I suppose...;-) I could as well say that if the
subject is viewed from a point in the center of the flat side of a
hemisphere and the image is projected onto that hemisphere, which
is then flattened for convenience (giving a fisheye image), that that
"proves" we see in spherical perspective... While this model would
better fit wide-angle views than the rectangular model (which falls
apart as the angle of view becomes extreme, and cannot support views
approaching 180 degrees, let alone those exceeding it [spherical
perspective can, as does our vision...]), it would still not prove that
this is a correct model, only that it is equally reasonable
within itself (though it does happen to offer fewer difficulties at
wide angles of view than the rectangular model...;-).
>If we could somehow project slides directly onto our retina without
>the aid of our own lens system, fisheye images might look more
>natural than rectilinear ones, but that is not the usual way
>to view slides.
No, you are right, but the little rectangles we are used to looking
at also do not look natural, especially when the view shown in the
image exceeds maybe 80-90 degrees... BTW, I think the argument that
is successful in all of this (rather conclusive, actually, that we
see straight lines off axis as curved [though not necessarily in strict
spherical perspective...;-]) is the fact that we can actually
see that straight lines off axis of our center of vision are curved...! ;-)
One easy example is available at a seashore. Look sharply up, while
paying attention to the bottom area of your field
of vision (while facing the water horizon), and you can clearly see
that the horizon line curves strongly...
(Sometimes it takes a lot to point out the obvious...;-)