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Re: [OM] Hyperfocal focussing?

Subject: Re: [OM] Hyperfocal focussing?
From: frieder.faig@xxxxxxxxxxxxxxxxxxxxxxxxx
Date: Mon, 1 Jul 2002 23:13:06 +0200
On Mon, Jul 01, 2002 at 10:15:27AM -0600, Sean Davis wrote:
> (de-lurking)
> 
> Could someone do me the favor of explaining the concept of "hyperfocal
> focussing" (don't know if i have the term right).  I have a small idea
> of what it's about, but don't really get it.  Does it have anything to
> do with the depth-of-field scale on a prime lens?  Every time i try to
> use that, i simply end up with a small focussed part in the middle,
> and everything else out of whack.  Confused!!


The concept is based on the following idea:

There is the depth-of-field-area in front of the focused plane, and 
one behind the focused plane. When the lens is focused at infinity
the depth-of field-area behind the focused plane is wasted 
(=ranges from infinity to infinity)

To get the maximum d.o.f , from infinity to the minimal possible 
distance is what "hyperfocal focussing is for". This means
to set the focussing distance so that infinity is just the upper 
border of  the d.o.f.-area. Therefore the use of the d.o.f.-scale 
on a prime is helpful. (setting the selected apperture-mark 
opposite to the infinity mark)
When I use hyperfocal focussing, I close the apperte usually one
stop more than the used-F-stop-mark to make sure infinty will be
sharp enough (  -> John L.`s good explanations)   

Frieder Faig
  
 



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