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: "R. Saylor" <rlsaylor@ix.netcom.com>
Date: Tue, 15 Jun 1999 13:23:02 -0400

> 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
> 
In your examples, the focus is indeed at hyperfocal. As you have  
observed, it's really nothing more than the closest distance you can 
focus in order to put infinity at the far end of the DOF. The near end 
will be one-half hyperfocal. 

It does depend on aperture as well as focal length. The narrower the 
aperture, the closer the hyperfocal distance. Hyperfocal also gets 
closer with shorter focal lengths.

I love to play around with the formulas (I'm a mathematician), but for 
some unaccountable reason, this doesn't help me make better 
photos. <g>

Richard S.