Archived posting to the Leica Users Group, 1997/10/01

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Subject: Re: Rangefinder alignment
From: Joe Berenbaum <joe-b@dircon.co.uk>
Date: Thu, 2 Oct 1997 03:27:10 +0100 (BST)

One other thing- the rangefinding function of the human head is by two
horizontally separated eyes, so possibly we think and function more
naturally in terms of horizontal orientation and placement in space. Alos-
being essentially ground-dwelling animals, we are more concerned, most of
the time, to avoid collision with obstacles at around ground level. So we
think in horizontal terms rather more than a fish or a bird would do. Maps,
for example, illustrate this preoccupation with the horizontal plane. A map
is a horizontal slice of a three-dimensional space.=20

At 21:37 01/10/97 +0200, you wrote:
>At 05:35 01.10.1997 -0600, you wrote:
>
>>Why doesn't vertical misalignment affect
>>focusing accuracy?  Is it just me, or do others find it more difficult to
>>focus the Ms vertically than horizontally?  I usually find that for a
>>vertical shot, I first focus horizontally, then realign the camera
>>vertically for the shot.
>
>You touch 3 different problems, first the misaligment effect, and both next
>the abilities of the human eye and the brain's management of visul input.
>
>1) The Leica's RF works horizontally. So, when you hold you camera
>orizontally, you can focus / estimate the distance (almost at least)
>correct, even if your RF's double picture is slightely dislocated in the
>vertical axis.
>
>2) The general advatange of horizontal vs. vertical perception in humans is
>known and follows a fundamental biological program, resulting from
>evolution. Enemies of humans could come from any horizontal  part/ axis=
 with
>high probability, but not or rather seldom from the vertical (e.g. from the
>sky).
>
>3) While teh sensibility in human's horizontal perception follows a
>bilogical ("hardware") program, the vertical perception needs to be llearnt
>or fixed within a very short period after birth (for some hours only, after
>some weeks or months, I don't remember the exact time), in a so called
>"sensible phase", and follows chaos theory. Any slight disturbance could
>result in def=EDcits, even severe ones (remember the "butterfly effect" ?).=
=20
>
>There are some clinical trials in which very young children crawled on a
>floor. The floor was not transparent, except for a 5 by 1 meter field of
>(invisible) glass stones. Here you could see the floor of the room below, 3
>meters down. The kids crawled from one side of the room to the other, even
>across the glass stone area without hesitation, since they couldn't differ
>vertically (were to young). They couldn't recognize the possible danger (to
>fall down), since they hadn't learnt it till then, and their horizontal bio
>programm didn't touch that part.
>
>Alf
>
>
>

Joe Berenbaum