Archived posting to the Leica Users Group, 1999/06/15

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Subject: Re: [Leica] Tri-Elmar and Depth of Field Hyperfocal distance
From: Mark Rabiner <mrabiner@concentric.net>
Date: Tue, 15 Jun 1999 00:58:05 -0700

"R. Saylor" wrote:
> 
> > This I understand. My question therefore seems to be how does one
> > calculate or even estimate just what that "as much infront of 'infinity'
> > as possible" might really be?
> 
> At hyperfocal, the far distance is infinity, the near distance is one-
> half hyperfocal. (This gives maximum DOF.)
> 
> If you set focus at infinity, the near distance is hyperfocal, the far
> distance is... who knows? The mathematics gives a negative number
> (the negative of hyperfocal, to be exact), which indicates something
> beyond infinity.
> 
> It has been suggested (by a Minox user, but I've lost the URL) that
> for distant scenes, it is better to focus at infinity rather than
> hyperfocal. The argument in favor of this involves perspective
> geometry, which is as much off-topic as Rolex, Mont Blanc, and
> Rolls Royce.
> 
> Richard S.

I've never thought I understood the Hyperfocal distance concept fully.
With a 35mm lens if I stick the infinity at the right at f16 I get
everything from 4' to infinity in focus and I am focused at 8'. I notice
4' is half of 8' as you say. You are saying 8' is the Hyperfocal
distance. And I guess it is only the Hyperfocal distance at f16. 
With a 35mm lens if I stick the infinity at the right at F11 I get
everything from 6' to infinity in focus and I am focused at 12.' So the
Hyperfocal distance changes with each F stop am I right? I keep hearing
about how each lens has it's Hyperfocal distance which confuses me as it
would change with each F stop. Unless I have it wrong. Which would mean
I am hopelessly ensnared in a circle of confusion!
Mark Rabiner