Bill is correct, up to a point. Many SLR lenses have scales
based on 5x7 prints. For each size larger using the mark for the
next larger aperture works well. OTOH, the human eye can
perceive a dot (circle of confusion) only so small, a smaller
dot is not visible. DOF is based on that size dot. So, trying to
get deeper DOF than that is an exercise in futility. But, as
always people will believe more is better even if it isn't.
--Tom
"Bill D. Casselberry" wrote:
> What you are doing, in effect, is reducing the size of the
> circle of confusion in the DOF calculation by this method.
> This allows "percieved depth of focus" to be better in a
> given size print or equally satisfactory in a larger print
> in relation to the DOF scale.
>
> A good tactic when needing clear DOF in oversized prints or
> superior DOF in "normal size" prints. The scales are generally
> set up with modest print size in mind.
>
--
Tom "Graywolf" Rittenhouse
Graywolf Photo, Charlotte, NC, USA
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