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Re: [OM] Definition of "Normal"

Subject: Re: [OM] Definition of "Normal"
From: Ken Norton <ken@xxxxxxxxxxx>
Date: Wed, 11 May 2011 11:01:53 -0500
AF wrote:
> Straw man indeed but the point I was making was that the eye is a very 
> different thing.
> That peripheral vision is critical to the way that the eye and brain operate.

I believe we are mixing intents as well as definitions when we try to
imply that a "normal" lens somehow mimicks the overall
angle-of-coverage of the human eye.

If I recall correctly, the angle-of-view of the lens considered
"normal" is actually defined by the typical viewing experience of the
displayed image. Inotherwords, the print size, as viewed from a proper
distance will yield a similar angle-of-view as if you were viewing the
subject in real life.

Let's take an extreme wide-angle shot of some body's face. The nose
will be massive and distorted of the print is viewed from a typical
distance, but if you get in really close to the print, it will
actually look proper. If you make that print poster-sized you can view
it from about arm's length and it will seem pretty normal, but walk
across the room and the nose is overpowering.

On the flip side, if you take an extreme telephoto shot of something
and view the print up close, it won't look "normal", but if viewed
from a distance it will.

Therefore, "normal focal lengths" are defined by the standard print
size and viewing distance, not some whacky "the eye sees this"
nonesense.

The book "Vision and Art - The Biology of Seeing" by Dr. Margaret
Livingstone, went to great lengths covering this and other topics. She
describes how the rules of perspective came through by emperical
evidence rather than mathematical equations. The mathematical
equations were developed to support what was already determined long
before photography came into existance.

I believe this is born out in the great masterworks as displayed in
the Louvre. The massive murals tend to have a wide angle-of-coverage,
whereas the smaller pictures--including the Mona Lisa, have a narrow
"telephoto" angle-of-coverage. By the way, it is absolutely necessary
to view the Mona Lisa at a specific distance because that is what
causes the smile to change when you look around the picture. It
exploits the center-sharp, blurry-edge characteristic of human vision.
Stand too close (impossible with the real thing) and the picture
flattens to the point where the face almost inverts. Stand too far
(more likely because of the ever-present crowd) and the smile doesn't
change.

AG
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