At 09:53 7/2/02, Dan Lau wrote:
Excuse my ignorance, but this description sounds like you are just
using the "depth of field" to keep the subject in focus. I thought
hyperfocal goes beyond what the normal depth of field provides.
-Dan
No.
It is "normal" depth of field at maximum possible depth for a given focal
length, aperture, and maximum acceptable circle of confusion diameter,
which defines maximum acceptable *un*-sharpness before perceiving it as
*un*-sharp. If the rear boundary depth of field equation is rearranged and
solved for critical focus distance at which the rear boundary distance from
the camera position approaches infinity (becomes infinitely large), it
reduces to the hyperfocal distance equation.
Be cautious if using lens markings to set a hyperfocal focus
distance. These are usually based on a liberally large circle of confusion
diameter on the order of 0.030mm to 0.033mm (on the film). This might be
sufficient for many people in small prints (3.5x5 or 4x6) viewed at about
14 inches. However, it will not be sufficiently small for *all* people
(some of whom have greater than average acuity), and this insufficiency
goes up with size of print. I work with 0.025mm or smaller circle of
confusion diameter which requires stopping down as much as a full stop from
many lens markings (e.g. using f/8 markings for an f/ll aperture setting).
-- John
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