Re-opening an old technical discussion:
My whole understand of DOF has been enlightened
and the explanations I provided earlier were in
serious error.
#1. DOF is directly tied to the opening of the diaphram. This is the major determiner
of DOF.
Lens design affect is somewhat, but that's a secondary effect.
#2. As a result, a 150mm lens on a 4x5 and on a 35mm will have the same DOF at a given
aperture.
What is different is the image coverage between the two formats, and that takes us to
the next matter.
#3. The issue becomes material when we're talking about relative magnification, i.e.,
the filling of a frame. If the object fills a frame the same between 35mm and 4x5,
there's a (roughly) 4-stop DOF difference that needs to be compensated for by
(a) adding more light, (b) adding more time, or (c) a combination of both.
I hope this is helpful to someone.
--
Collin Brendemuehl, KC8TKA
-----------------------
"Get over it."
Dr. Laura
--
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