Archived posting to the Leica Users Group, 1999/06/14

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Subject: Re: [Leica] Tri-Elmar and Depth of Field marks
From: Martin Howard <marho@ikp.liu.se>
Date: Mon, 14 Jun 1999 16:32:02 +0200

"Richard J. Wyble" wrote:
> 
> 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?
> 

I don't know the maths, but a rule of thumb is that if you have a 
depth of field spanning X feet with a certain aperture when focused
at a point Y, then 1/3 of X is going to be in front of Y and 2/3 is
going to be behind it.

So, the hyperfocal distance is the distance Y at which infinity is
placed just at the very edge of the 2/3 zone for any given aperture.


M.

- -- 
Martin Howard, Grad. Schl. for Human-Machine Interaction,  |
HMI/IKP, Linkoping University, SE-581 83 Linkoping, Sweden.|    Just
Tel: +46 13 28 5741; Fax: +46 28 2579; ICQ: 354739         | say "DOOH"
E-mail: marho@ikp.liu.se; www.iav.ikp.liu.se/staff/marho/  +------------