Archived posting to the Leica Users Group, 1997/12/17

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Subject: [Leica] Re: [Lieca] Infinity focus tip
From: Jim Brick <>
Date: Wed, 17 Dec 1997 11:23:43 -0800

At 01:49 PM 12/17/97 -0500, Pete and Bob wrote:
>Infinity is the thing that describes how positive integers there are in the
>Its a few other things too, but that gets too technical.
>As far as lenses go, I'm not sure what the optical definition is... :)
>-----Original Message-----
>From: <>
>To: <>
>Cc: <>
>Date: Wednesday, December 17, 1997 1:41 PM
>Subject: Re: [Leica] Infinity focus tip
>>Dear Colleagues,
>>I would like to hear more discussion on the nature of Infinity, both in
>>technical and field contexts. I've never heard a convincing definition of

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D  ANSWER =

Merriam Webster states:

Main Entry: in=B7fin=B7i=B7ty
Pronunciation: in-'fi-n&-tE
Function: noun
Inflected Form(s): plural -ties

1 a : the quality of being infinite
  b : unlimited extent of time, space, or quantity
2   : an indefinitely great number or amount
3 a : the limit of the value of a function or variable when it tends to
become numerically larger than any preassigned finite number
  b : a part of a geometric magnitude that lies beyond any part whose
distance from a given reference position is finite <do parallel lines ever
meet if they extend to infinity>
  c : a transfinite number (as aleph-null)
4   : a distance so great that the rays of light from a point source at
that distance may be regarded as parallel=20

After digesting the above definitions, I believe Brooks trained me
correctly. It is my belief, both from schooling and experience, that if you
set a lens on the infinity stop, open the lens wide open (f/1.4 or f/2) and
take a picture, basically nothing in the picture is truly in focus. Maybe
"acceptable" focus, but not within the bounds of what we would call
"critical" or "good" focus.