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Re: [OM] Binary DoF

Subject: Re: [OM] Binary DoF
From: Sandy Harris <sandyinchina@xxxxxxxxx>
Date: Thu, 23 Oct 2014 12:08:01 -0400
Ken Norton <ken@xxxxxxxxxxx> wrote:

> The comment was made that DoF and Hyperfocal calculations are based on
> a binary decision: It's either sharp (in focus) or it isn't. I highly
> disagree with that assessment. ...
>
> The history behind the DoF calculations (and lens markings) is based
> on the viewing of a standard size print observed from a standard
> viewing distance. It's not a binary thing, but extremely variable ...

I know he is far from a popular man on this list, but Ken Rockwell
has a page on this topic that seems to me (far from expert) to
make sense: http://www.kenrockwell.com/tech/focus.htm

Anyone care to critique that? Or point to a better resource?

A method I have used with a reasonably fast prime (f2.0 or
better) is to just pick something at a good distance (infinity
focus), open the lens as wide as it will go, shorten focus
until I can see blur, lengthen it a smidgen to eliminate the
blur, stop down to f5.6 and shoot. I'm reasonably happy
with results, but wonder if there is a better way.

Also, that method won't work for a slower lens. Does
anyone have a good suggestion for those?
-- 
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