Greetings!
I'm trying to reenter photography (well as much as the kids will allow)
mostly using my OM equipment. And I realize that I don't know the answer
to a question that had been nagging me decades ago!
I find the d.o.f. preview button not very useful since my eye can't
resolve near focus distances with sufficient precision in the viewfinder
(I bet yours can't either). So using a non-visual calculation of d.o.f. is
often useful to me. The markings on the lens are a good starting point for
estimates, but I would love some rules of thumb to work from those.
To wit, how are the depth of field indicators on Zuiko lenses calculated?
Basically, they need to arbitrarily decide on a value for the Circle of
Confusion. Is this 30 microns for all lenses (I read somewhere that this
is fairly standard in the 35mm format, but I can't recall the reference
or estimate its reliability)?
Since the allowable value for the circle of confusion should vary with the
anticipated enlargement (and to a lesser degree film speed/graininess), it
would be useful to be able to reestimate d.o.f. for different values of
the c.o.c. from the lenses as well. Is there a way to interpret e.g. the
f8 mark as giving the f8 depth of field at 30 microns, but the f16
indicating the same f8 depth but at ~100 microns?
Similarly, any tricks for extended lenses (especially with the 14 and 25
mm rings)? I find that my sense of d.o.f. is almost always off from the
finished product with my very amateur macro work (mostly with the 90mm f2
portrait lens which does a decent job pretending to be a macro lens)
I'll happily summarize off-list replies, but this group seems to do
everything on-list... :-)
Thanks in advance!
Eric
=====
Eric Pederson
epederso@xxxxxxxxxxxxxxxxxxxx (no "n" in "epederso")
Professional home page:
http://logos.uoregon.edu/uoling/faculty/pederson/pederson.html
Personal home page:
http://darkwing.uoregon.edu/~epederso/
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