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.
Optics work in a plane of precise focus with an established rate of
defocus the farther from the plane of focus. As you stop a lens down,
it changes the rate of defocus. I've talked about how modern lenses
have more of a zone of in-focus, and that's somewhat true because the
use of fancy optics to warp the effective rate of defocus. But
generally speaking, the entire concept of DoF and the mathematical
calculations have their basis in emperical testing, not pure math.
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 as
it depends entirely on arbitrary criteria and viewing experiences.
Through extensive testing, the industry did establish the DoF
calculations as a guideline, which is still quite appropriate when the
output and viewing experience matches the testing environment.
AG
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