Archived posting to the Leica Users Group, 2001/02/10

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Subject: Re: [Leica] DOF: Erwin
From: Shan <shan@montana.net>
Date: Sat, 10 Feb 2001 15:23:19 -0700
References: <4.2.0.58.20010210111614.009b1990@mail.web-you.com> <007b01c09440$58cfb900$273334d1@default>

Well, being mathematically impaired myself, I can't answer that linear part 
without some empirical testing. I have always _assumed_ that it was linear. 
I (think I) know that with respect to image magnification, it is indeed 
linear, i.e. a 150 focuses @ infinity at 150mm from the film plane and @ 
1:1 at 300mm. Well I'm gonna go drag my camera out and do some focusin' and 
cypherin' ... I'll be back

shan

At 08:14 PM 2/11/01 +0100, Tim wrote:

> > then
> > placing the lens exactly between these two points per references on
> > the focusing track, then selecting the appropriate f/stop to cover it,
> > i.e. 1/2 in front...1/2 behind.
>
>But focus isn't linear WRT the position on the rack. If you move the
>lens mount to halfway between your focus for near and far
>distance, you aren't focussing on a point midway between the
>objects, no?

In reply to: Message from Shan <shan@montana.net> (Re: [Leica] DOF: Erwin)
Message from "Jacques Bilinski" <jbilin@axionet.com> (Re: [Leica] DOF: Erwin)