Archived posting to the Leica Users Group, 2003/08/21

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Subject: Re: [Leica] focusing (was zone f.)
From: "animal" <s.jessurun95@chello.nl>
Date: Thu, 21 Aug 2003 13:01:35 +0200
References: <1061441185.93d7c060leicanews@myrealbox.com> <p05100301bb6a529a6e3a@[80.9.119.232]>

I think you,d have to focus on the father because of the flat field as  you
say.But i,m not sure.
simon
- ----- Original Message ----- 
From: "Christer Almqvist" <chris@almqvist.net>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Thursday, August 21, 2003 12:43 PM
Subject: [Leica] focusing (was zone f.)


> (resending this message)
>
> OK, I  know the answer to this question could be: 'go and do some
> test shots', and also that the question may be slightly on the
> theoretical side, but anyway, here we go:
>
> Imagine for a second that you want to make a picture of three people
> standing on the other side of the street. The street is 4 meters
> wide. One of the people, let us call him 'the father' stands directly
> opposite you on the curb, four meters away from you because you also
> stand on the curb. Also on the curb on the other side of the street
> from you, but three meters to the left of the father is his son, and
> similarly, three meters to his right is his daughter. Obviously the
> children are five meters away from you.
>
> In this situation most people using an M will focus on the father
> because he is so conveniently located  right there where the little
> yellow window is, that we use for focusing. Others will focus on the
> father because they have heard something about flat film plane and
> they take that to mean that everything at a 'picture plane' paralell
> to the film plane will be at the maximum sharpness if the distance
> set equals the the minimum distance from the film plan to the picture
> plane (i.e. measuring at 90° from camera to picture plane).
>
> Now imagine you want to take a picture  of just the children, but
> with the children remaining in their original position. In this
> situation, most people would focus on one of the children (and thus
> set the distance to 5 meters) and then reframe the picture to include
> both of them. With the flat film theory as I understand it, the
> children would not appear as sharp on the negative as they would had
> you not refocused, i.e.  they would have appeared sharper on the
> negative had you not changed the distance setting from 4 to 5 meters.
>
> Please tell me what is right and wrong in the above. Please do not
> tell me that it does not matter because it will be covered by depth
> of field, because I know that is not true, at least not for large
> lens openings.
>
> Rgds
>
>
> -- 
> Christer Almqvist
> D 20255 Hamburg and / or
> F 50590 Regnéville sur Mer
>
> please look at my NEW  b+w pictures at:
http://www.almqvist.net/chris/dozen/
>
> old pictures still at:     http://www.almqvist.net/chris/new
> --
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In reply to: Message from "David Degner" <leicanews@myrealbox.com> ([Leica] Photo Story)
Message from Christer Almqvist <chris@almqvist.net> ([Leica] focusing (was zone f.))