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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