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[OM] DoF Compared

Subject: [OM] DoF Compared
From: usher99@xxxxxxx
Date: Wed, 11 Aug 2010 22:47:42 -0400
JS writes:

"Having studied -- and taught -- this stuff for a long time, all my
research indicates the DoF depends *solely* upon the focal ratio and
reproduction ratio. Period. That leads me to agree that any other
perceived difference in DoF is an aberration -- in other words, the
lens that appears to have less DoF is simply softer, or has different
bokeh, or has some other distortion coming into play.

I'm willing to be convinced otherwise, but having a reference citation
in the optics literature would go a long way toward convincing me!"

Good point--wonder if someone actually has published a full wave optics 
solution in lieu of the very simplified
geometric model used in all the dof calculators.  I am not sure how to 
find that as I don't routinely search that literature.
On the other hand as dof by its very nature is an artificial construct 
with subjective features, it may be overkill.  If the nature of the 
aberrations result in
the rendering of areas in front of or behind the plane of focus as 
appearing  sharper, then for all intents and purposes the dof is 
larger, IMO.
I have no trouble believing the complex beasty lenses today in some 
fashion deviate in their behavior in real world use from equations 
derived using the simple lens equation.
I am amazed how useful that simplification and dof scales resulting 
 from that remain.   I'll study AG's shots carefully and take note.  Dr. 
Focus's concerns duly noted.

A seein is believin, Mike

-- 
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